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Vince Virgilio
04-11-2010, 07:21 AM
Hello,

Warning, I'm real green. And it's not easy being green.

I'm installing 20"x20" porcelain tiles in a 13'x13' room. The subfloor is bare plywood with 16" joists; it's a very firm floor. Between the tile and plywood, I'll use DITRA with DITRA-Set.

I haven't laid any tile yet, and only cut the DITRA to fit. I did mix ~ 12 lbs of DITRA-Set and troweled it onto the plywood with a v-notch trowel. Apparently, the mix was too dry, and I had to remove it---there was minimal, if any, adhesion between the DITRA-Set and DITRA felt. This threw me, as I was very careful with proportions of water/dry-set in following the instructions on the DITRA-Set bag, i.e. 5-6 qts water / 50 lb bag, then scaling down to 12 lbs.

So I decided to run small experiments on a loose piece of 2'x2' 3/4" plywood, until I had a working solution. The first of the succes criteria would be proper adhesion between the plywood and DITRA felt.

I mixed a small amount, 1 lb., of DITRA-Set with more than the recommended amount of water (~ 6.5 oz, instead of ~ 4.2) until I had a cake-batter like consistency. This gave much better wet adhesion between the plywood and felt than my original attempt. I let it dry overnight. This morning I discovered that I was able to peel the DITRA from the plywood, with a little force. I think that means Failure. Please find attached a photo of the problem---poor adhesion between DITRA felt and plywood using DITRA-Set + water (not Latex).

So, again, I've done something wrong. And I suspect that I should have used a Latex additive instead of water. (I'm using water instead of Latex, contra bag directions, because of some advice I decided to follow, even though the advice was rushed and perhaps misunderstood my question.)

If I should mix in Latex instead of water, which Latex should/could I use with DITRA-Set? I'll experiment again on the loose 2'x2' plywood square. I'd like to continue this project today, so ideally the Latex would be available at a big-box store, which are the only ones around here open on the weekends. I don't think the '425' or '427' types of additives indicated on the DITRA-Set bag are available at the big-box stores, though I could be wrong about this too.

Could someone confirm that I've indeed mistakenly used water instead of Latex with the DITRA-Set on the plywood subfloor? Seems obvious now, but I'm wondering if the poor adhesion here could be blamed on something else, like a too-wet DITRA-Set mix.

Thank you for your time and attention,

Vince Virgilio

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John Bridge
04-11-2010, 07:39 AM
Welcome aboard, Vince. :)

Ditra-set is an excellent thin set, but it is not specified for plywood. For plywood you need a "modified" thin set that Ditra-set is not. Ditra-set should be used to set the tile to the Ditra, though. :)

Return to where you bought the Ditra-set and tell them you need a thin set that works on plywood. Or you can got to Lowes or Home Depot and buy a "modified" or "fortified" product. I'll warn you, though. The folks at the big box stores know next to nothing about thin set, so choose your product by reading the back panel of the sack. :)

Vince Virgilio
04-11-2010, 07:46 AM
John,

Thank you very much. I'll do so.

So the Latex additive, replacing the water, would not be sufficient to adhere DITRA felt to plywood.

I am the poster-boy for this now.

Regards,

Vince

jgleason
04-11-2010, 07:48 AM
And...looks like the mix is still a little too stiff. Also - you will be able to peel Ditra away from the substrate, even after a day. Peeling it up is not a valid method of testing. Get the proper thinset mixed loose but still able to hold a notch. Comb it out on the floor, lay the Ditra and embed it firmly. Peel back a corner to ensure you are getting 100% coverage with no ridge markls, aka tiger striping.

If you go to HD pick up Versabond for setting the Ditra to the plywood. Mix it with water, it is a modified thinset.

Definitely stay with the DitraSet for setting the tiles. :tup2:

DerekCr
04-11-2010, 07:49 AM
Priming the plywood might help too, but the ACRYLIC admix will definitely do it. You might end up needing a 3 gal. bucket of it so big box might be out of the question.

"APPLICATION
SCHLUTER-DITRA INSTALLATION: For plywood substrates,
mix with 425 Multi-Purpose Acrylic Latex Admixture or 447
Flex-A-Lastic Admixture. For concrete, gypsum, mortar bed,
and cement backer board substrates, mix with water only."

Vince Virgilio
04-11-2010, 07:51 AM
The turn-around time on this board is phenomenal. With excellent advice into the bargain. Fathom it.

Vince Virgilio
04-11-2010, 08:00 AM
@ DerekCr

Yes, those are the bag-instructions I referred to. The DITRA-Set bag suggests it can be used over plywood. But if, by my reckoning, it gave unreliable (overly general?) advice on the water measure, then perhaps it could mislead the uninitiated about plywood substrate as well.

Hum.

Vince

DerekCr
04-11-2010, 08:10 AM
The addition of the admix makes it "modified" which is required to go over plywood, admix or Versabond as suggested will do it. The adhesion properties of "modified" is greatly multiplied over the non modified. I would also recommend a universal primer but some might say that is going overboard. If you can't get the admix, save the Ditra Set for the tile and use the Versabond for the plywood.

Vince Virgilio
04-11-2010, 08:11 AM
Hello,

Can DITRA be cut into smaller pieces, say 3-4' lengths, for more convenient handling, without compromising its integrity (uncoupling ability, etc.)?

Or does DITRA work better in larger monolithic pieces (fewer cuts)?

Vince Virgilio

Vince Virgilio
04-11-2010, 08:14 AM
Derek,

Do you anticipate any problems over the areas where I removed (scraped off) the too-dry mortar? I used a razor-like 6" wide paint scraper for removal. Photo attached.

Thanks,

Vince

DerekCr
04-11-2010, 08:22 AM
No, it will actually help with the bonding, but won't be necessary with the modified.

Davestone
04-11-2010, 09:12 AM
Honestly i don't think it matters as long as it's not tiny pieces.

Crestone Tile
04-11-2010, 09:18 AM
As long as the area to be tiled is thoroughly covered by Ditra, it doesn't matter the size or how it's pieced in.

If it needs to be waterproof, that's a different story.

cx
04-11-2010, 09:47 AM
Welcome, Vince. :)

Please keep all your project questions on this thread so folks can see what you're working on and what's been previously asked and answered.

We can give it a more generic title any time you'd like to suggest one.

The bags of Ditra Set known to me are pretty clearly marked as exceeding ANSI A118.1 when mixed with water and A118.4 and A118.11 when mixed with one of Hydroment's latex additives. Pretty much the paragraph Derek posted above.So the Latex additive, replacing the water, would not be sufficient to adhere DITRA felt to plywood.That would not be correct. With the additive it would be more than adequate for the task.

My opinion; worth price charged.

dhagin
04-11-2010, 11:40 AM
If you haven't priced it, the cost of the additive alone will likely be more than the cost of a bag of modified for sticking Ditra to ply. I'd pick up a few bags of modified and return the Ditraset you don't use.

Certainly won't hurt to use the additive, but not needed IMO. :)

Vince Virgilio
04-11-2010, 03:37 PM
Again, I really appreciate all of the help in this forum.

I purchased a bag of Versabond, and am going to run the same test that I did earlier with DITRA-Set.

I have a V-notch trowel, where each side of the V is 7/32" long, and the top or opening of the V is 8/32" wide. (photo attached) Is this appropriate for Versabond between plywood and DITRA, or would someone recommend another?

Thank you,

Vince Virgilio

cx
04-11-2010, 04:26 PM
VersaBond's fine for installing your Ditra.

That 1/4x3/16" vee notch trowel is still on Schluter's recommended list for installing Ditra, I believe.

My opinion; worth price charged.

Keeney
04-11-2010, 10:02 PM
I would go slightly bigger on the trowl. From the photos, it looks like it is not even wetting, much less sticking to the felt on the ditra. Gray thinset will make it much more obvious where the felt is saturated and where it is still dry (there should be no dry spots if you pull it back up).

I ended up re-doing several sections of ditra I had stuck down with too small of a trowel. If stuck down properyl yes, you can peel it off, but you will have to wrk at it - it won't be loose to the touch.

Here are some of the things I did:

- pre cut all the ditra to fit the room(s)

- used a 1/4x1/4 square trowel.

- mixed the mud fairly wet to the point the ridges would just hold without slumping.

- only mixed 1/2 bag at a time to make sure I could use it up while still sticky.

- only spread out about 1/2 of the 1/2 bag worth of mud before embedding the ditra. Absolutely did not let it skin over.

- lots and lots of pressure with a 12" piece of 2x4 used to press and slide across all surfaces of the ditra, embedding it into the mud. I made sure I could actually see the mud everywhere through the back of the ditra - the gray mud helps with this a lot.

- used versabond.

- did't worry about the extra mud squishing out the edges and seams or smeared over the top - I cleaned that up with a wet mop after the ditra was firmly embedded.

Vince Virgilio
04-12-2010, 08:00 AM
Keeney,

Thank you very much for the considered advice.

I ran another experiment on a 20"x20" patch of DITRA, where I used Versabond between it and the plywood. As many suggested it would, the adhesion improved dramatically. When I pulled the DITRA up, most of the felt would not release from the Versabond, but ripped off the DITRA! Excellent, I think.

However, my mud technique is still lacking. When I applied the Versabond, the "wet" adhesion was spotty, at perhaps 80%. I didn't create full trowel V ridges (3/16") everywhere, so had to fill the low spots and retrowel. 1 lb + ~ 5.6 oz water was barely enough for the 20" square.

Which raises another point. I made the Versabond into a pancake-like consistency. This seemed correct, but only obtained with a more water than indicated on the bag. 5.6 oz / 1 lb = 8.25 qts / 50 lb bag, instead of bag instructions which call for 6 qts / 50 lb bag.

Perhaps pancake consistency is too loose. But it would seem to work fine as long as I make consistent ridges. On the other hand, I think the DITRA-Set mix between the tile and DITRA needs to be thicker, say, the consistency of peanut butter at room temp.

So a couple of Qs:

1. Is there an easily communicated technique that would improve the consistency of the V-notch troweled Versabond ridges? I'm not sure if a deeper notch would help, if I'm not putting down enough material in the first place. (Though I'm inclined to use the deeper 1/4" notch.)

2. This one's almost self-talk. Why am I finding the recommended water proportion on the bags (both DITRA-set and Versabond) too dry?

2.5 Would you agree that "pancake" consistency is about right for the Versabond, and "room-temp. peanut butter" about right for DITRA-Set (between tile and DITRA)?

Again, thank you. This is a golden thread.

Vince

bbcamp
04-12-2010, 09:14 AM
Thinset is supposed to be a bit looser for setting Ditra and Kerdi than for setting the tiles. The bag instructions are for setting tile, and a peanut-butter consistancy is the way most describe it.

Vince Virgilio
04-12-2010, 09:25 AM
FYI,

This morning Schluter Support confirmed to me via email that, for non-waterproof installs, DITRA can be cut to smaller lengths without compromising its integrity. I asked specifically about 4' lengths, and the answer was 'Yes that would be completely fine.' I suppose there would be no problem with other lengths that don't approach DITRA's cell-size.

I also asked if the DITRA squares (cells) needed to line up across seams. The answer was: "No the DITRA squares do not have to line up. DITRA can be pieced together any which way. "

Vince Virgilio

jgleason
04-12-2010, 01:58 PM
Also, the water proportions on the bags are more of a guide to get the proper consistency for setting tiles. Relative humidity and temperature can also impact whether more or less water is used as well as variations in the product itself.

Vince Virgilio
04-17-2010, 04:01 PM
Thanks for all of the advice so far. When it's time, I'll use Versabond.

Now I need to rewind a bit, and ask about subfloor deflection and sheathing curvature.

There are two rooms. The subfloors in each consist of 2x10 (1.5x9.25) joists, which are 16" oc, covered with a single layer of 23/32" T&G exposure 1 SIF plywood.

Again, I intend to install 20"x20" porcelain over Ditra-set over Ditra over Versabond (over ?) in each room.

Dimensions of the first room are 13.5' x 13.5'. The Deflecto tool say this exceeds L/360 deflection requirements.

The shorter dimension of the second room is 17', in the direction of the joists. Deflecto says this does not met L/360 deflection requirements.

I am not sure if Deflecto's negative result for the larger room is enough to justify an additional sublayer of, say, 3/8" plywood. (If I do, I'll add it in the smaller room as well, to give equal height.)

Further, /both/ rooms do not pass the "jump test" for deflection (I'm not surprised). However, I've read article "Position of Underlayment to Prevent Cracked Tile and Grout", by Woeste and Nielsen, which suggests that curvature across joists is the driver in cracked tile and grout (not deflection?). A Schluter article (http://www.schluter.com/print/5140.aspx) supports this, showing that curvature along joists is ~ 10% X across joists. So the focus should be across joists, where oc spacing is key, not the span. This seems to dilute the negative results of Deflecto for my larger room.

The curvatures mentioned by Bretzfield and Woeste in Appendix VIII of John Bridge's "Tile Your World" have a minimum of 353 in (F147-02). Even without a sublayer, I think that magnitude of curvature would be undetectable to casual inspection. So I don't think there's a way to check the actual curvature of my floor, except to infer it from the specs I listed above. Unfortunately, the table of curvatures in that Appendix VIII does not include by joist spacing.

Can someone help me judge whether my subfloor has enough curvature to warrant a sublayer under the Ditra?

Thank you for your time and attention,

Vince Virgilio
04-19-2010, 10:04 AM
With Schluter's permission, here is their response to essentially the same question about adding a sublayer.

Schluter screibe:

Hi Vince,

Thank you for all of the detailed information. Your floor seems to meet our requirements, so I think you are good to go. Obviously, if there is anything out of place (such as the floor being very bouncy or damage), you would need to address that first.

Please follow the instructions in the DITRA handbook and let us know if you have any other questions.

Best Regards,


Customer Service
Phone (800) 472-4588
Fax (800) 477-9783
csrusa@schluter.com
www.schluter.com

bbcamp
04-19-2010, 10:21 AM
Vince, the 17 foot span of the joists in your larger room is too much for a tile installation. I can't think of a wood species that would allow such a span and meet the L/360 deflection criteria. Adding a layer of subfloor isn't going to solve that problem.

Schluter and the rest of the tile industry have decided to pass the buck on floor framing requirements and focus only on the subfloor. They do say that the framing must meet local building codes, and most building codes point back to the L/360 deflection criteria that the deflecto tool uses. My guess is that your house was built outside of any permitting jurisdictions, or before such niceities arrived in your area. Since your own observations indicate that these floors need stiffening, you should start looking for ways to do so, regardless of any need to add another layer of subfloor.

Vince Virgilio
04-19-2010, 10:29 AM
Thank you Bob,

Then there's a good bit more to think about the larger room. But I think that answers the question about the subfloor. The room is over a basement, so is it safe to say that any solution would be applied from underneath, and thus not raise the height of the subfloor?

In your opinion (as ever, no strings attached) do I seem ready to proceed with the tile in the smaller room, since Deflecto says it meets deflection reqs (L/416)?

Vince

cx
04-19-2010, 10:39 AM
Vince, the room size has nothing at all to do with the requirements for the joist structure. And I think we know nothing at all about this joist structure.

What is the type, size, condition and unsupported span of your joists under the areas to be tiled?

In your first post you indicate "The subfloor is bare plywood with 16" joists," but I'm not at all sure what you mean there nor do I see any indication of the span.

Need to get that sorted out before we can tell you much more.

My opinion; worth price charged.

Vince Virgilio
04-19-2010, 10:47 AM
CX,

Got it.

The smaller room, 13.5' x 13.5' is over an inaccessible crawl space (no basement), so I don't know how to verify that the subfloor structure is identical to the larger room with the 17' span. My guess is that it is identical. But perhaps I can remove some house siding and squeeze underneath to check . . .

That larger room has 2x10 joists, spaced 16" oc, covered with 23/32" SIF, exposure 1 plywood. The longest span is 17'. The lumber has markings of "Mar 86". To my untrained eye, all wood appears to be in excellent condition.

Would more specs help? What am I missing?

Thanks.

bbcamp
04-19-2010, 01:50 PM
"Mar 86" may have been a good month for lumber, but even if it was select Douglas Fir (the grade and species of the lumber), the joists are overspanned for ceramic tile. The fixes are below the plywood, e.g. you must either shorten the span, increase the thickness or decrease the spacing of the joists so that each one is responsible for less of your floor and can thereby deflect less.

Not trying to beat a dead horse, but your tile work will be only as good as the supporting structure, and your structure isn't all that good, at least in the bigger space.

Vince Virgilio
04-19-2010, 02:01 PM
Bob,

Understood.

I'm actually considering a beam/post assembly underneath in the basement, to half the span. That might be the easiest, even with new concrete footings.

Complete sistering would be difficult against the ductwork. (But if piecemeal sistering would give a predictable improvement, I'd consider it.)

And, apparently, bridging/blocking is only effective at maintaining or approximating the span's theoretical performance, i.e. by keeping joists more vertical. I don't think bridging/blocking can improve over theoretical performance. Or not enough to give comfortable margin.

bbcamp
04-19-2010, 02:05 PM
Adding a support beam is the best bang for your buck. Do you need some help sizing it?

Vince Virgilio
04-19-2010, 02:07 PM
I will certainly need help spec'ing that thing . . .

bbcamp
04-19-2010, 02:14 PM
A beam made from 2 2x8s with support posts every 8 feet or less will work.

Vince Virgilio
04-19-2010, 09:12 PM
Bob,

I've attached a rough schematic of the two rooms I intend to tile. A couple of highlights:


Notice the proposed beam/post position. Any further toward the middle of the 17' span will intrude on a door opening (not shown

The 13.5'x13.5' room joists appear to be on concrete footings, over earth, not basement.


What do you think of this beam placement? Also, could I use a steel I-beam, instead of wood, for added strength and possibly thermal + moisture stability?

bbcamp
04-20-2010, 05:02 AM
The beam placement is fine. It gives you a maximum unsupported span on the long side of about 11.5 feet, which is within reason for 2x10s.

The joists must rest on the basement walls for you to consider the walls as support. Shim if the joists are not in contact with the wall.

If you want to use a steel beam, a C 3 x 5 (Channel, 3" deep, 5 pounds/ft) is the smallest you could go with. I'd consider using a C 5 x 6.7 if you could find it. It's a little deeper, about 1/3 heavier, but 4 times stiffer, which should make your floor happy. There are angles that will do the job, but I don't like them for this application, since they will be harder to mount between beam and post, and they tend to twist under load. There are also small I-beams that will work. An S 3x5.7 or M 4x13 would be good choices.

There's nothing wrong with using sawn lumber or engineered wood for that beam. If your basement has moisture or thermal issues that would affect the stability of a wooden beam, you've got bigger issues than tile for your floor.

What ever you do in the larger area, I'd do the same thing in the smaller area.

Vince Virgilio
04-20-2010, 05:09 AM
Thanks Bob,

The smaller area is not accessible from underneath or the side. It's about a 3 ft. footing. If I were to reinforce that floor, I see no other way in except through the top, by removing plywood. Agreed? At that point, sistering might be easiest . . .

Vince

bbcamp
04-20-2010, 05:22 AM
Maybe. I've seen guys dig footers (http://www.johnbridge.com/vbulletin/showthread.php?t=6821) while standing between the joists so they could reinforce the floor with a beam. It depends on how much interference with wiring, plumbing and HVAC you have to deal with.

In my own house, I have a portion of the crawlspace that is difficult to reach through the existing access door. I cut a new one in the foundation (standard 8" blocks, hole is 1-1/2 blocks wide and 3 blocks high) at the end of the house (non load bearing wall). I lived in my house for almost 20 years before doing it, and now I kick myself for not doing it sooner.

Vince Virgilio
04-20-2010, 07:43 AM
Bob,

The thread you linked was inspiring!

My concrete "footers" (barely know what I'm talking about) under the smaller room appear to be poured. They don't appear to consist of blocks. Also, they're less that 3': somewhere between 2 and 3, I guess.

How do I determine if the footers are load bearing? In my case, there is no 2nd level over the smaller room---it's a single level.

Back to the linked thread . . . I like the idea of digging between the joists. Just don't know how I'd get a full length beam in there, without pulling up a full "plus pattern" of plywood. But then, perhaps I should, to maximize the learning experience.

Thanks again!

bbcamp
04-20-2010, 09:34 AM
My concrete "footers" (barely know what I'm talking about) If you can see them, you can take a picture and post it. Then, we'll both know what you are talking about. :D

The beam in your smaller room doesn't need to span the entire room in one piece. You can support the ends from a single support post. For your 13.5 foot dimension, you can set three posts 6.75 feet apart. Two beams would span between the two outer posts and meet at the middle one.

Vince Virgilio
04-20-2010, 09:39 AM
If you can see them, you can take a picture and post it. Then, we'll both know what you are talking about.

Will do, after work.

Two beams would span between the two outer posts and meet at the middle one.

Got it.

Thanks,

Vince Virgilio
04-20-2010, 05:42 PM
Bob,

Here's a picture of the footer. The wall on the left is from the smaller room; the wall on the right is not the larger room.

Concrete height between dirt and siding is 16 inches. I don't think that'd be a good way under the floor. It's short, and it seems like it'd lose integrity if I cleared a hole through it.

Again, there's no second level over the left wall (but there is over the right one).

bbcamp
04-21-2010, 04:48 AM
OK, it looks like your options are to remove the subfloor and do any strenghtening from the top, or switch to vinyl or carpet. Assuming vinyl or carpet option is not viable, we'll need to see what interferences you might have in the joist bays that would make sistering a bad idea. I guess it's time to remove some subfloor.

While you have the subfloor out, check for any vapor barrier on the ground, and install one if necessary.

Vince Virgilio
04-21-2010, 07:24 AM
No vinyl or carpet. The only way out of this is straight forward.

I thought I'd try to scope the problem better with some minimally invasive surgery. Maybe a hole large enough for a trouble light and camcorder (a live feed). Just the hole should allow me to verify joist dimensions.

If there are no surprises, then the whole subfloor comes out? I think that involves a toe-kick saw to separate it from the wall plates. That becomes a permanent separation, since new subfloor would screw to new blocking on the inside of those plates (against the outermost joists, including the band joists?), and would not be integrated with the plates as was the original subfloor. Would this separation from the plates weaken the overall strength of the room?

(Again, my vocab is weak. I don't know if I should call the bottom horizontal 2x4 of a wall a "footer" or a "plate", or something else.)

bbcamp
04-21-2010, 08:41 AM
Depends on what you will eventually do about the joists. You may be able to remove only the middle sheets and work the material in, then close it up.

Get some pictures and we'll sort through the options.

Vince Virgilio
04-21-2010, 08:53 AM
Will do.

Should I cut the via in the middle of the room? That way, if it turns out that only the middle sheets need to be replaced, the hole would be automatically repaired.

Aside, I'm wondering how to do a partial replacement of T&G plywood with more T&G, into a rigid hole; does the T&G on the new pieces get sacrificed?

bbcamp
04-21-2010, 08:57 AM
Good thinking on hole placement.

Where you piece in a section of subfloor, you install blocking to support the cut edges. This can be as simple as a length of 2x4 laid on the flat, and straddling the cut. Screw and glue it to the underside of the fixed piece, then glue and screw the patch in.

Vince Virgilio
04-21-2010, 08:58 AM
Do patches compromise rigidity of the subfloor?

Thanks,

cx
04-21-2010, 08:59 AM
Patching T&G almost always involves removing a tongue or tongues and installing blocking under those joints. It's not difficult.

I would rarely bother buying T&G plywood for such a repair.

My opinion; worth price charged.

Vince Virgilio
04-21-2010, 09:02 AM
To remove a tongue, run a circular saw at correct depth along the tongue (edge)?

bbcamp
04-21-2010, 09:17 AM
Yes, or save a dollar and buy straight edged plywood.

Vince Virgilio
04-21-2010, 09:46 AM
I'll buy sheets without T&G, if available.

And during removal, I think I could free adjacent sheets locked by a tongue, by running the saw along the tongue at correct depth.

Also, is there significant risk of joist damage, when the glue between the joist and plywood pulls off? If so, would more careful prying action reduce that risk?

Thanks,

Vince Virgilio
04-21-2010, 10:32 PM
Bob,

The crawl space under my smaller room is all concrete. No dirt.

The joists are exactly 9x1.5, again 16" oc.

Pictures attached. The break in the concrete wall is under the entry to the smaller room, from the kitchen.

Under the floor, I see only insulation, some wiring for the security system, and a couple of (possibly) speaker cables. No other electrical, and no plumbing.

The concrete floor of the crawl space does not appear to be level.

Beam and post looks like the best solution. But would there be a way to avoid sinking new footings, and using the existing concrete? Are there semi-permanent self-leveling jacks with which I could support a beam under the span?

On the other hand, sistering is still an option. Except I don't know how I'd get the lengths under the floor.

bbcamp
04-22-2010, 04:43 AM
Change "post and beam" to "load bearing wall." A very short load bearing wall. Same effect on your joists, the load is spread out over the slab. As I see it, the live load this wall will be responsible for is about 475 pounds per foot of wall. No big deal unless the slab is only an inch thick. Drill a test hole or two to check, then fill them with some mortar.

Normally, a load bearing wall has some sort of sheathing on at least one side. As short as yours will be, that won't be necessary. Just use a pressure treated sill plate (2x4) on the slab, and 2 top plates, with studs every 16 or so inches apart. For this, it may be easier to mount the plates to the slab and joists, then cut studs and toenail them in.

Vince Virgilio
04-22-2010, 05:01 AM
Bob,

I've never built a wall before, so some questions:

1. Would you recommend a certain bit to use in a 3/8" drill to test the depth of the concrete, or do I need a different drill?

2. How do I attach sill plates to the concrete?

3. Should the top plates be attached to each other first before being attached to the joists? If so, with screws and glue?

4. Can I make the top and bottom plate in a couple or few segments?

Thanks again,

bbcamp
04-22-2010, 05:35 AM
1) A masonry (carbide tipped) drill bit in a standard 3/8" drill will work. A hammer drill would be better, though. I wouldn't go out an buy a hammer drill for this, unless you needed it elsewhere.

2) Tapcons. Concrete screws. You will need to drill some more holes, but again, a standard drill will work. You need a screw every 24 to 36 inches, just to keep the sill plate from moving as you toenail the studs. After that, gravity takes over.

3) No, attach the topmost piece to the joists (glue and screw), then cover with a second 2x4.

4) Segments. Use stud grade 2x4s for this. They are not the best lumber in the yard, but they will be good enough and cheap enough for this. Make sure the second 2x4 overlaps the joints in the top 2x4 by at least one joist bay. It's not essential that the ends of the top 2x4 end on a joist, nor is it essential that the studs align with the joists. On the other hand, you are toe nailing the studs, so you can put them where you want them.

As for toenailing, you can use screws instead of nails. Might be easier in tight quarters than swinging a hammer.

When fitting the studs, try to cut them to fit snug without lifting the floor. Don't create a new problem solving an old one. OTOH, if the floor has any sag in it, now would be a good time to correct it.

Vince Virgilio
04-22-2010, 06:03 AM
Got it.

I forgot to ask about the mortar mix to refill the pilot holes. What is "mortar" in this context?

I have an open bag of Versabond. If that would do, should I use the amount of water indicated on the bag (scaled down)?

Thanks,

bbcamp
04-22-2010, 07:46 AM
I was deliberately vague because any mortar will do. Just take a scoop (say about 1/2 cup) of powder and add a little water until it looks good, them smoosh it in the holes. It won't take much because your holes needn't be very big, just large enough to know when you stop drilling through concrete and when you start drilling in the dirt. If you drill more than a couple of inches without hitting dirt, you can stop, 'cause that's deep enough.

Vince Virgilio
04-22-2010, 08:53 AM
I'm willing to purchase a hammer drill if it will help later with the beam/post install under my larger room.

Would I be able to bolt those posts into the concrete? Or will they require concrete cut-outs and new footings?

Thank you,

cx
04-22-2010, 09:13 AM
The sorta concrete I think we're seein' in them pichers is not usually structural in nature, Vince. Usually more to cover and protect the vapor barrier installed over the dirt in the crawl space. I'm thinkin' it's not likely suitable for the base of a structural support.

But I been wrong before, 'specially when lookin' at the pichers posted here on the site. IzzOK, somebody alla time will correct me. :)

Do tell what you find it to be.

My opinion; worth price charged.

Vince Virgilio
04-22-2010, 09:21 AM
Interesting.

So the crawlspace floor and walls are poured separately, and possibly with different materials/mixes. (I'm creeping along the learning curve.)

Most of the basement is finished, and appears to be load bearing; I think this is obvious, as there are two levels above it, and I don't think /all/ of the load is carried by the outer walls. The unfinished part of same basement (with load bearing walls, correct?), under the larger room, shares the same floor as the finished part. Does this suggest that the type of concrete used for the basement, /not/ the crawlspace, is structural?

Lookin' for a guess to guide my thinking.

Thanks CX,

bbcamp
04-22-2010, 09:34 AM
Vince, until you poke a couple of holes in it, we're all just guessing. Sometimes builders will apply a very thin layer of poor concrete over the dirt just for appearances, errosion control, or some other non-structural reason. Good, finished concrete is not cheap, so they don't use it unless there is a good reason to.

If the concrete isn't thick enough for the wall, we're back to the beam and footers. The good news would be that the slab will be easy to bust out for the footers.

In the basement area, you could use a concrete pier block to spread the load from the posts, and you could add a third post to reduce the loads. It depends on the concrete in that area, so you'll want to drill some test holes there, too.

Vince Virgilio
04-22-2010, 09:36 AM
Understood. Will do.

Thanks,

cx
04-22-2010, 09:38 AM
What Injineer Bob said.

Vince Virgilio
04-22-2010, 10:45 PM
Bob,

I drilled three 5/8" holes in the slab under the smaller room, along where a future sill plate might go. The holes at either end had a depth of about 5", and the hole in the middle had a depth of about 4-5".

I drilled another 5/8" hole in the basement under the larger room, just about where one post might sit, next to the door. Its depth was about 3.5".

I had to apply some serious effort on the 5/8" wide, 6" long masonry bit to break through the slabs with my 3/8" drill. Demo, for me, would be horrendous, if not impossible.

Can these concrete floors reliably support the loads I'm considering?

Thanks,

Vince Virgilio
04-24-2010, 09:21 AM
Based on what Bob wrote earlier, I think the ~ 4-5 in. thickness of the slab under the smaller room is sufficient.

Bob wrote,

As I see it, the live load this wall will be responsible for is about 475 pounds per foot of wall. No big deal unless the slab is only an inch thick [emphasis mine].

So, unless I hear otherwise, I'll proceed with the construction of this wall.

Though it's still not clear to me if the ~ 4" slab depth of the basement under the larger room is sufficient to support a beam and couple of posts.

Thank you,

jgleason
04-24-2010, 05:53 PM
Hi Vince,

Thought you were doing a short wall with double top plates as Bob suggested, yes? The slab you've got will be adequate for that. The wall will distribute the load more evenly on the slab than a couple of posts and a beam.

Vince Virgilio
04-24-2010, 06:01 PM
Hi Joe,

I wasn't being clear.

Yes, I'm putting the short wall under the smaller room.

But, I think, 1 ~ 8' beam / 2 posts under the larger room span. Wondering if I need to put anything under those posts. Or, if they were adjustable steel posts, could I just anchor them to the concrete with a couple of 3/8" "concrete bolts"?

Thanks for the response,

bbcamp
04-26-2010, 04:37 AM
Use concrete pier blocks, like the ones used for decks, to spread the load under your posts. Set them in a bed of brick mortar.

Vince Virgilio
04-26-2010, 07:28 AM
. . . Set them in a bed of brick mortar.

Thanks Bob!

Do you think I should cut out a square of concrete for each footing, to fill with that bed of brick mortar? Or form the brick mortar bed on the existing concrete?

Seems that the first option at the following link would fit, which I think uses precast concrete piers (over the above brick mortar bed).

http://www.countryplans.com/foundation/index.html

bbcamp
04-26-2010, 09:25 AM
Use the "pre-cast pier on grade" idea, but put the pier on your slab, using a layer of brick mortar to level it and keep it from moving. No need to cut your slab.

Vince Virgilio
04-26-2010, 09:31 AM
Understood. And will do (when I get to it).

Thank you,

Vince Virgilio
05-01-2010, 08:59 PM
I used two pieces for each layer of the top plate (~ 8' and 6', overlapped by 2 bays), and intend to use two pieces for the sill plate, again ~ 8' and 6'.

However, with the wood placed, I just noticed that the floor is uneven enough to give gaps of up to 1" between the sill and concrete. I hesitate to try to pull those closed with Tapcons.

So while I am ready with the Tapcons, I thought I would instead set the sill plate in mortar. That would both fill the gaps, and keep the sill in-place for toe-nailing. It would also give me a level sill, which sounds like a good idea.

If this doesn't raise any red flags, could someone advise on the mortar? I have a bag of Versabond open. I found it patched the pilot holes fine, and also a crack in my sidewalk, so I thought it might apply between the sill plate and floor as well.

But does Versabond have enough load-bearing capacity? If not, should I use the brick mortar recommended earlier to set the pre-cast piers?

If I can go ahead with this, is there a recommeded consistency?

Thank you again,

cx
05-01-2010, 11:57 PM
Vince, I'd be afraid you'd just knock that mortar all apart when you tried to nail in your studs to that bottom plate. For sure if you try that you don't wanna try using anything like thinset mortar, though.

Our customary method of leveling up stud walls over uneven SOG is to shim it where necessary with wood wedges cut from dimension lumber. These wedges will be 8 or 9 inches long and taper maybe from 1" or 1 1/4" to nothing. You just drive as many under the bottom plate as necessary to make the top plate level and flat. You could likely use some construction adhesive on your shims to flatten out your sill plate and let it set up before you try to stud in your wall. Or you could shim the plate level and drive some small nails through the plate into the shim to hold it in place. I'd use the pookey, too, if I did that.

Ain't gotta be pretty, just gotta be sound, eh? If it look like you'll need lotsa shims, use lotsa shims.

I use KDAT lumber for my sill plates and for those shims.

My opinion; worth price charged.

Vince Virgilio
05-02-2010, 07:05 AM
Thanks CX, then shims it is.

By the way, the lumber I bought at Menard's was stud-grade and was marked as Kiln-dried. Does that qualify it as KDAT?

I'll be back,

bbcamp
05-02-2010, 08:45 AM
No. If you look at pressure treated lumber, you notice the green color from the preservative chemical. Dry treated has about the same look, but it is dry from the kiln instead of being soaking wet like pressure treated wood.

If you can't find KDAT lumber, use regular pressure treated, but find the driest and straightest boards you can find. Use extra fasteners because this wood will try to warp.

Another method would be to install some sort of barrier between regular kiln dried lumber and the floor. A couple strips of roofing would may work. Building inspectors may not find this acceptable if they looked, though.

Vince Virgilio
05-02-2010, 11:11 AM
Understood.

Should I be concerned that the Kiln-dried (not KDAT) top plate will absorb moisture and warp over time? I don't know year-round humidity levels in the crawl space.

I think probably not, since I don't think the wood (say, the 2x4 studs) in other unfinished parts of the basement are KDAT. At least, there's no mark that reads "KDAT". And those share the same air-space with the crawl, via the broken-out hole visible in one of the original pictures I posted of the crawl. (Don't know if air-flow restrictions might prevent the two spaces from ever reaching equilibrium.)

Thanks,

cx
05-02-2010, 01:16 PM
I would not worry about the KD top plates at all, Vince. That crawl space, if not conditioned or partially conditioned, should be well ventilated. If it's not, I'd wanna correct that.

My opinion; worth price charged.

Vince Virgilio
05-02-2010, 01:51 PM
Perhaps ventilation is the reason for the broken-out part of the wall, that leads into the rest of the house.

I'm callin' it good.

Thanks CX,

Vince Virgilio
05-05-2010, 09:35 AM
I found some KDAT. Very elusive. ~ $3.80 / 2x4x8'.

The yards mentioned Borate as a safer alternative (blue wood, I think), and cheaper by a few cents. They say Borate is not a wet product.

Can anyone confirm that Borate wood won't warp, in the same way KDAT won't?

Thanks,

bbcamp
05-05-2010, 09:49 AM
Depends on how they apply the borate solution. If they soak the wood in it, then bundle it for delivery, I'd say it would warp. If they stickered and dried it after treatment, then it's the same as KDAT. If they spray kiln dried lumber with it, then allow the excess to run off and the wood to dry, then there would be some chance of warpage, but not to the degree that regular pressure treated lumber does. I sprayed my joists with a version of the stuff with out noticeable warping.

cx
05-05-2010, 10:23 AM
Not sure what they expect the borate to keep you "safer" from, Vince, but it's not gonna prevent rot as is the intent with the pressure-treated woods. Borate will keep bugs from eatin' your plates, though.

If your slab was poured with a vapor barrier under it, a good quality KD lumber will last your lifetime under there unless you have some other water-infiltration problem.

I'd still buy the KDAT.

My opinion; worth price charged.

Vince Virgilio
05-05-2010, 10:31 AM
There's no water infiltration that I see. But, now that I've spent the effort on finding it, I'll just go with the KDAT.

I think Borate is safer because it doesn't contain arsenic, as pressure-treated wood does.

Thanks again,

cx
05-05-2010, 10:48 AM
Highly unlikely that you would encounter any treated wood containing arsenic (CCA) at your local lumber yard these days. Or any non-local yard.

Far more likely you'll find ACQ treated wood, which contains no arsenic.

Look at the little plastic tag likely stapled to the end of your KDAT lumber for those letters. I'll bet heavily on ACQ.

My opinion; worth price charged.

Vince Virgilio
05-10-2010, 06:47 PM
More-than-expected shimming necessary to achieve level.

Does the below picture show any structural sins? Or can I go with it (after I cut about 2X more such shims)? The spacing is ~ 6". Off the left side of the photo, not shown, the 2x4 gradually becomes flush with the slab.

I thought I'd tie it together with 1 1/4" brads (pneumatic: clean, easy, no disturbance) and a lot of construction adhesive. I could even put 2x4 blocking in most of the gaps under the 2x4 to the right.

cx
05-10-2010, 10:32 PM
I would make no attempt at all to achieve level in that manner. You got no need whatever for that plate or plates to be level, you can cut your studs to fit whatever space you end up with. I'd lay the plate on the concrete and shim only where there is no contact.

When I spoke of shimming wall plates like that (but not even close to that extent) it was for walls that area assembled with pre-cut studs and rolled into place after being constructed. We'd drive shims like that under gaps where necessary to level and flatten the top plate, but you've got a whole different game going there.

Lay your plate(s) on the concrete, and fill in the studs such that they're snug top and bottom. You can then shim under the bottom plates if you have some gaps under there still.

Sorry if I aided in misleading you, but what you have in that picture is not what I'd wanna do in your situation.

My opinion; worth price charged.

Vince Virgilio
05-11-2010, 05:11 AM
And I thought those little stacks were Things of Beauty. :)

No, obviously, I pushed the idea too far.

I understand the correction, and will "adjust".

Thanks again,

Vince Virgilio
05-12-2010, 06:20 PM
I think this is the way to shim.

The studs are spaced about under every joist, except where I had to slide one way or the other to get positive pressure.

I thought I'd shoot brads into the studs/plates to stabilize, then toe-nail. Then, thin nails through the bottom plate into the shims? And if glue, where? Between the shims, on the shims (before insertion) or both?

Before securing the shims, I'd thought I'd tap them in in a bit, carefully. Again, to obtain slight upward pressure on the floor. Unnecessary or not advised?

Thanks,

cx
05-12-2010, 11:49 PM
I like to pewt some pookey on both sides of the shim before final installation, Vince. You can poke in a brad if the shim wants to slide back out before the glue sets, but with the shims you have there it shouldn't be a problem. Just takes a little dab.

Lots of ways to skin that cat, mine is just one.

Looks much, much better this time. :)

The shims wanna make everything tight without moving anything. Unless, of course, something needs moved.

My opinion; worth price charged.

Vince Virgilio
05-26-2010, 07:18 PM
I've finished the supporting wall in the crawlspace, and am now replacing the 4x8' (nominal) sheet of subfloor I cut through for access. The original subfloor consists of T&G, width 47.5". The replacement piece is not T&G, and is 48" wide. So I ripped off what I thought was a 0.5". The actual cut is about 1/8" deeper in the middle. That, combined with some tolerance in the original cut-out of the T&G give a 0.5" gap between one side of the new piece, and the existing adjacent piece! The gap on the other side of the new piece is ~ 1/8".

If I can, how should I proceed with the 0.5" gap, to install DITRA over it? Do I need to plug it, or mesh over it, or when applying the modified thin-set, just try to fill the gap with that?

Thanks,

bbcamp
05-27-2010, 05:02 AM
Vince, consider the sheet you cut incorrectly as practice. Cut a new sheet to fit with the proper 1/8" gaps.

You are doing a lot of work, and spending a lot of money. Don't ruin it over the price of a sheet of plywood.

Vince Virgilio
05-27-2010, 05:30 AM
That's what I thought. Add it to my scrap pile, and and start over, more carefully.

Thanks Bob,

bbcamp
05-27-2010, 05:33 AM
Measure twice, cut once. ;)

Vince Virgilio
05-27-2010, 08:24 AM
Some detail for other amateurs . . .

I used a 100 in. rip fence (2 pc. aluminum, by Swanson), securely fastened to each end of the plywood, at carefully measured points, even accounting for blade width. I might have measured the fence alignment three times.

I wonder if the fence bowed in the center, where the pieces abutted (and are bridged by a third short segment). I only checked fence alignment at the edges, not in the center. This time, I'll also check the center, and the 1/4 points as well. Heck, maybe I'll spend some lead on this, and strike a line.

Vince Virgilio
06-02-2010, 11:41 PM
I finally closed the subfloor with a 4x8' sheet of BC plywood, max 1/8" gap on edges and ends. Glue between it and the joists, and > 2" deck screws as frequently as the original nails. I put the screws almost exactly between the original nail holes, as well as between the perimeter nail holes and adjacent plywood. I pre-drilled the new holes.

This time, I tapped in a few nails behind the rip fence (half and quarter pts) to eliminate any deflection, in addition to the C-clamps at each end. That gave a very consistent rip.

I notice in perhaps two places that the edges of the old and new plywood are not quite level, by max 1/32". I'd think that tolerance would be compensated by the modified thinset.

Q1. Should I sand the adjacent edges of new/old plywood until level?


Q2. Do I need a second layer of plywood, for 16" oc joists? I couldn't figure this out from the liberry. The current T&G subfloor appears to be in excellent condition. However, there is the "disturbance" of the new piece, which is not T&G. I'm concerned about adding much extra height to the floor, since there's only 1 3/8" between the subfloor and bottom of a french door which swings into the room. That clearance, I suppose, could increase with some woodwork on the door (not something I think I could do well). The tile is 3/8" thick.

Thanks again,

bbcamp
06-03-2010, 09:18 AM
1) I wouldn't, but it can't hurt if you did.

2) If you added blocking at the edges of your new plywood, then no, you don't need a second layer. If you didn't, you need to add at least 3/8" more plywood, and make sure you provide plenty of fasteners at the un-blocked edges.

Vince Virgilio
06-03-2010, 10:32 AM
Thanks Bob,

I didn't block the new plywood. But I discovered that there is limited access to the crawl space from an adjacent area in the basement. So I think I could still add blocking. From underneath, I'd try to glue in blocks that span new/old edges between joists. Then, while the glue is still pliable, drill through the subfloor into the blocks from above. And finally, apply the same deck screws as used on the rest of the new plywood. I suppose there'd be some difficulty in keeping the block in place while I drilled from above. Maybe I'd fix them better with brads, either "toe-nailed" through each block's corner into the subfloor, or (better?), shot from above.

Yes, I'm trying to avoid the additional layer of plywood. But if there is significant risk without it, I'll use it.



Again, I want to expression my appreciation to this forum for its excellent information, advice, promptitude, and civility. In my case particularly to John Bridge, Bob, and CX. I've recently run across similarly good forums elsewhere, but this one shines.

cx
06-03-2010, 11:25 AM
Your blocking for the between-joist joints in the subflooring needn't be attached to anything but the two sheets of plywood, Vince. Doesn't hurt to attach the blocking to the joists, but it's not necessary. I frequently use six-inch wide rips of 3/4" plywood for such blocking. Pre-drill, glue and screw from the top. Couple screws from the bottom hold it in place whilst properly attaching from the top.

My opinion; worth price charged.

If you've found other useful forums, feel free to name names. We alla time have folks looking for information on other subjects. Other tile forums are fair game, too. :)

Vince Virgilio
06-03-2010, 11:33 AM
So, to be remedial:


From underneath, fasten blocks with glue and a couple of (short) screws.
From above, to finish, predrill and screw?

dhagin
06-04-2010, 08:05 PM
1-yep, just to hold em in place while you screw from above
2-yep. Pre-drill probably not necessary.

Vince Virgilio
06-06-2010, 11:33 AM
Dana,

Thank you; got it.

CX, to name a name, the on-line Journal of Light Construction has a Ceramic Tile forum with some interesting info on DITRA installs, i.e.
http://forums.jlconline.com/forums/forumdisplay.php?f=13

Best,

cx
06-06-2010, 11:53 AM
Very familiar with JLC, Vince, although I rarely spend any time over there any more. Usta hang out in the trim carpentry forum quite a lot.

Do say hi to our friend Michael Byrne when you visit their tile forum. He and ol' JB are buddies from way back. :)

Vince Virgilio
06-06-2010, 01:26 PM
Not at all surprised by any of that!

By the way, there shouldn't be a problem using pieces of the old plywood for my blocking? They have some nail holes, but otherwise appear sound. (They're already cut.)

cx
06-06-2010, 02:15 PM
Old plywood's fine, long as it's thick enough and in good condition. I like 3/4".

My opinion; worth price charged.

Vince Virgilio
06-06-2010, 02:17 PM
Ah good---it's the original 23/32" (3/4) that I pulled up for access.

Vince Virgilio
06-06-2010, 08:59 PM
The blocking is in, with three screws on each side of the old/new edges between each pair of joists. Three seems to be enough. If no corrections, I'll proceed with the Versabond at pancake batter consistency for the DITRA. I intend to work with smaller areas this time to avoid skinning---I'm slow.

Also, I found a good bit of glue on my crown; I must've rolled in it while I was in the crawl. It peeled off, but took a good few chunks of my already meager hair with it. I hope PL Premium isn't super-potent enough to cross the blood-brain barrier and neuro-tox me.

Houston Remodeler
06-06-2010, 09:04 PM
If PL Premium were that toxic I'd be dead by now and the last time I checked, I'm still doing ok.

To help avoid skinning over don't use a fan, keep the a/c vents from blowing on the fresh thinset. I know its not comfortable, but I think that's why they call it 'work' :uhh:

Vince Virgilio
06-07-2010, 07:59 AM
Thanks Paul,

Good reminder---won't be a problem to work that way. At least I'll have daylight. Probably.

Don't know what it is with glue lately, but I just added a thick layer of Elmer's Super to a couple of fingers this morning, just before work, and no acetone in sight.

Vince Virgilio
08-22-2010, 08:58 AM
Use the "pre-cast pier on grade" idea, but put the pier on your slab, using a layer of brick mortar to level it and keep it from moving. No need to cut your slab.
__________________
Bob



I'm about to build the beam/post assembly to reduce my ~ 17' span to ~ 11', and am going to follow Bob's advice. Though before I begin, I need a clarification or three.

1. How thick should I make the layer of mortar? Above what thickness would I need to form it?

2. Will a thicker layer of mortar provide more strength? If so, is this important in this application?

3. Instead of mortar, could I simply use construction glue (liberally)? I imagine this would be too thin to provide any leveling. But if leveling is unnecessary, this might suffice to constrain lateral motion? (Still, I want a long-term solution.)

Again, thank you.


(No, no tile in anywhere yet. I've been . . . preoccupied.)

cx
08-22-2010, 09:18 AM
I went back about four pages and couldn't find that quote by Injineer Bob, nor the discussion of adding piers. Thought you took care if your joist support with that shimmed-up little wall under the floor. What am I missing?

Vince Virgilio
08-22-2010, 01:07 PM
CX,

Yes, I put the short wall under the small room.

But there's a larger room with a 17' span, which I'm going to reduce to ~ 11.5' with posts and beam.

Bob's advice for the post/beam assembly starts around here:

http://www.johnbridge.com/vbulletin/showpost.php?p=943866

Here is the schematic from me:

http://www.johnbridge.com/vbulletin/showpost.php?p=944072

More beam/post advice from Bob:

http://www.johnbridge.com/vbulletin/showpost.php?p=944144

and continues here, where Bob mentions piers and brick mortar:

http://www.johnbridge.com/vbulletin/showpost.php?p=946602

through here:

http://www.johnbridge.com/vbulletin/showpost.php?p=946673



Thanks,

cx
08-22-2010, 01:17 PM
OK, I just didn't go back far enough.

The mortar is just to provide a 100 percent footprint for your pier blocks, Vince. No, you don't wanna use construction adhesive, you want some sorta cementitious product.

If the floor is very level and flat, you could set the blocks in some thinset mortar. But if the blocks require some leveling, use the brick mortar as Bob suggested. You don't want it any thicker than it takes to level the block and give it a solid footing.

My opinion; worth price charged.

The Kid
08-22-2010, 01:51 PM
Im not sure if this has been said earlier but 2 things you can do to strengthen what you plan to do.

1)sheet at least one side of the support walls you are building below. THis will decrease lateral moveing in wall.

2)Fasten all joist to new wall plate to reduce independant movement of floor system. Toenail 2 16d nails per joist or simpson huricane tie.

cx
08-22-2010, 02:14 PM
The support wall he built is only about 18" tall, Jason. He posted some photos of his repair a few pages back. Not much sheathing required. :)

Vince Virgilio
08-22-2010, 06:57 PM
Thanks Jason! Your advice is still well-taken.

CX, should I attach the beam to the joists above, or just leave friction between the two?

Thanks,

Vince

cx
08-22-2010, 08:23 PM
Attaching the joist bottoms to the support beam is always a good eye-dee, as Jeremy suggests. As in nearly all parts of a subfloor structure, I favor screws for that application.

My opinion; worth price charged.

Vince Virgilio
08-31-2010, 08:11 AM
It looks like I'm going to use 4x4" wood posts to support a beam of two 2x8's (screw/glue). The beam will attach to the joists above and 4x4 posts below with some commodity Strong-Tie fittings I found in the lumber aisle at Lowes. The 4x4's would be treated lumber (no untreated 4x4s in sight) from around same aisle.

Now, I'm strongly considering replacing the concrete piers between posts and floor with some simple metal fixtures. Each is like a shoe for a 4x4 post, with a flange on the bottom. The flange has four holes, one in each corner. The shoe comes with a few lag bolts. (But I thought I'd replace those with large tapcons?)

The concrete floor under the 4x4 posts is in very good condition (~ 4.5" smooth slab), and is probably very level.

So the question is, can I use the metal shoes described above, as a long-term solution?

Thanks,

bbcamp
08-31-2010, 09:04 AM
Yes you can, since you verified the thickness of the slab. The piers were suggested to spread the load and reduce the stress on the slab. However, I think it might be easier to mortar the pier blocks than to drill and install the tapcons.