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Motordoctor 02-10-2015 06:10 PM

5 Attachment(s)
More pictures down the tunnel between the joists.....

cpad007 02-10-2015 07:48 PM


That's what I call a "Whole Lotta Fun!"


Motordoctor 02-10-2015 08:42 PM

Yeah, I'm thinking that putting tile in the kitchen isn't a good idea. The reason for it was to pretty up the house for sale, not to rebuild the whole house, one room at a time. The underlayment needed replacement, had a couple of rotted sections from water leakage. Took out a couple of the planks too. So that's not a total loss. Other than all the time I wasted trying to scrape off the old tile/glue/felt/schmutz/etc. The final fix was just to saw through the old plywood and pry it off. I spent less time prying up the whole floor than I spent scraping 1/4 of it. Like I said, it's a real shame because I think the tile would have made the kitchen. Now I have to figure out what to put down instead.

I've heard of vinyl tile that looks like ceramic with grout lines, may look into that. I put some snapstone tiles in the basement kitchen, problem with them is the floor (concrete) isn't flat and still has old vinyl tile glue on it that won't budge. I tried every chemical I could but nothing would budge that crap off. Heatgun, scraper, putty knife, etc. I first tried putting down some self adhesive vinyl tiles after putting a primer down, looked good for a couple of days and then the edges started to lift. Pulled those off, and tried putting a good contact cement on the tile and the floor. Same result, stuck good for a couple of days, then the edges started curling up. Lowes was having a sale on the Snapstone tiles, thought that might be a solution but since the floor isn't flat enough, the tiles rock. That project has been on the backburner too until I figure out what to do about that. Since the concrete floor seems to be the problem, and the area is too small to get any serious power equipment in there, I was thinking the only solution was SLC under the snapstones but I don't know if the bond issue is going to be a problem. So far the score is Tiles 2, Me zero.

A couple of old sayings come to mind:
You can't make a silk purse out of a sows ear.
If you don't have time to do it right, when will you have the time to do it over?
And of course this one :good advice is often given but seldom taken.
Being a motorcycle mechanic, I have to make that decision often. Do I spend an extra hour on the gasket surface to get it 100% or would spending 10 minutes to get it to 90% do the job? What it comes down to is this: what's it going to take to replace that gasket and do it right if it leaks. If it's easy, I will take the chance, if it's a PITA, then I take the time to do it right.
Putting 140 sq ft of tile down only to have to redo it a couple of months later isn't worth the risk.

cx 02-10-2015 08:56 PM

Lot of tile pros have learned that sometimes the job you make the most profit on is the one you walk away from. Most of'em learn the hard way, though. :)

Motordoctor 02-16-2015 12:51 AM

Well, I haven't given up on it yet. Just spent the last two days replacing the water heater. Never did one before, so it took me a while. I tried those flex hoses that HD sells since I figured #1 they look cool and #2 lots faster then measuring/cutting/cleaning/soldering copper pipes. Not a good idea. Never could get them to quit leaking at the water heater joint. As soon as you put water pressure to them, they would leak. Tried all I had to throw at it, could slow it down to a slow trickle but not the thing to have. Oh well, live and learn.
So the wife decided that she would really like the tile in the kitchen so I guess I need to make it work. Happy wife=Happy life. So on with the questions.

I'm going to take up the subfloor (diagonal planks from the 40s) and replace it with 23/32" Plywood. I've seen reference to the tongue and groove style but of course I don't see it at HomeDepot. Structurally that better than just plain (meaning not T&G) 3/4" plywood of the proper grade? Georgia Pacific makes the Sturd-I-Floor Plytanium and listed HD as being a vendor but it's not listed on their website. They do list a couple of other local lumber yards so I have to call to see if it's available.

Do you recommend gluing the subfloor to the joists as well as screwing it down?

Since I'm going to have access to the joist with the subfloor off, I can block and sister to my hearts content more or less. Are there some links on the proper way to sister a joist/blocking or should I say how to sister a joist in this instance? Does blocking help with the deflection issue?

So my current plan is now 3/4 AKA 23/32" plywood subfloor laid 90 degrees to joists, 1/2 AKA 19/32" plywood underlayment over that and 1/4" Hardi with a modified thinset over that. Gives me about 1 5/8" total thickness between the joists and the tiles.

Since I'm trying to stack the deck in my favor, I was wondering about a couple of other options.

Is the Ditra more forgiving if the floor is flexing? It says it's an uncoupling membrane but does that make your tile install more forgiving of a marginal floor? Since it would take about $275 worth of the stuff to do the job, is it money well spent in this case? If I put down the Ditra, would I put it over the Hardibacker, or just straight onto the plywood.

Do the modified medium bed mortars that are "flexy" AKA Flexbond/Megalite/Reflex/etc helpful here? Local procurement is limited to HD/Lowes/Bostik. Thanks again for your help.

cx 02-16-2015 11:51 AM

1. You must either have T&G panels or you must install blocking between panels at the between-joist spans. The T&G is usually easier, except when the confines of remodeling make it difficult to install correctly.

2. Yes. As a rule I prefer to glue every part of a subfloor installation. An exception is when plywood is installed over sawn boards or OSB.

3. Form your photos,you're gonna need to remove some of your wiring and probably move some plumbing to do any meaningful sistering. I'm still of the opinion that simply improving the wall you have in place is the easier and more effective method of reducing deflection in your application.

Between-joist blocking does nothing at all to improve design deflection of the joists.


Originally Posted by Dan
1/2 AKA 19/32" plywood underlayment over that...

. Nominal 1/2" plywood will be marked as 15/32nds" thickness.

If you have room for 19/32nds" plywood I would not remove the existing subflooring, but would install the nominal 5/8ths" (19/32nds") plywood over the existing diagonal board subflooring, saving a whole lot of labor and some material cost.

Originally Posted by Dan
Gives me about 1 5/8" total thickness between the joists and the tiles.

That total is not relevant at all, Dan. The important criteria is what is making up the subflooring thickness.

5. If the floor is flexing, you have a problem regardless the tiling substrate you elect to use. There is no industry standard for uncoupling membranes, so we can't really tell you what they will/won't do. The manufacturers have their own test data and their own subflooring requirements. Meet the requirements and their products should function as advertised.

6. There are no medium-bed mortars. There are thinset mortars (thin-set being a method, not a product type) whose manufacturer's allow their use in thicknesses above the industry standard maximum of 1/4-inch in some applications. The manufacturer's will tell you what to expect from each of their mortars.

My opinion; worth price charged.

Motordoctor 02-16-2015 01:26 PM


If you have room for 19/32nds" plywood I would not remove the existing subflooring, but would install the nominal 5/8ths" (19/32nds") plywood over the existing diagonal board subflooring, saving a whole lot of labor and some material cost.
So when I put down the 19/32" plywood over the existing planks, do I treat it as underlayment or subfloor? Meaning do I only screw it to the existing subfloor and not the joists? Thanks again for your advice.

cx 02-16-2015 01:30 PM

It's a second layer of subfloor, no matter what you call it, Dan, and you'll want to fasten it only to the board subfloor below after you've ensured proper fastening of those boards.

My opinion; worth price charged.

Motordoctor 02-17-2015 05:44 PM

I think I may have a solution here. Putting a mid-span beam under the joists in the basement. I talked to the guy at Ellis Manufacturing about it and he suggested using a 4x4 with their screw jacks to shore up the floor. Probably take about an 8~9ft piece of wood to do it (the beam). The screw jacks use a 4x4 as an upright to the bottom of the beam with a Purlin Splicer to attach it to the beam. The distance from the floor to the bottom of the joist is 84". If I can buy them around here, I was thinking that I should put a concrete pier under each jack to spread the load since I have no idea how thick the basement slab is. If not I guess I need to make a couple of them. On a google search they show up @ Home Depot but there's no price/availability.

They also have the option of using 3 2x6" side by side as a beam also. If I really wanted to get fancy I could make a wood I-beam using 4 2x6" screwed and nailed together. As far as the jacks go, would two of them be enough for a 8 ft beam or should I go with three? After looking at them, I could probably make those things way cheaper than buying them but getting metal around here is a real pain in the ass.

Sound reasonable? I took a good hard look at the existing wall in the basement and it's pretty flimsy looking. It's 2x4s with a single side of drywall. There should be enough room for me to put the beam right next to that wall, probably have to compromise a bathroom closet a little but what the heck.

Reinforcing the existing wall would really be a pain, half of it is more or less easy to get at. The other side is behind the furnace/water heater/return duct. I'm just looking for the cheapest/easiest/quickest solution so I can sleep at night not worrying that I really should have done more than I did. When you don't know what you're doing, overdoing it is better than under-doing it, eh? Ask anybody that wastes money on synthetic oil and changes it every thousand miles. I tell them if it lets you sleep better at night, go for it!

cpad007 02-17-2015 06:01 PM


Do you have any settling issues? I'm not quite sure why you'd need to use hydraulic jacks at all to add the support wall unless you need to lift several joists a bit. I suppose you could lift things a tiny bit, build your wall, and then let the jacks down to settle on the wall.

I think I would just build a regular old double-top plate 2x4 wall of whatever length you need, 16" oc studs. One thing you need to be sure about is the support from your foundation. You might also toss some 1x material at an angle across it for lateral stability or put up plywood. You might further be clever by using the wall for something useful like a closet or something.

Or are you looking to simply put a beam in with two posts and not really a load-bearing wall?

Motordoctor 02-17-2015 06:41 PM


Or are you looking to simply put a beam in with two posts and not really a load-bearing wall?
I just want to sleep at night knowing I did all I could to stop the dreaded cracked tiles/grout. The reason for the screw jacks is probably a stupid one. I don't have faith in myself to cut the uprights to the right length without a bunch of tries. Using the jack, it only has to be within 6" and I'm sure I can do that :) And if the floor needs some adjustment from sagging I can always crank a little up in a particular spot. I'm worried that cutting them a little long and whacking them into place will cause flatness issues on the floor. Although for the price of those jacks I might consider giving it a whirl since 4x4 posts are pretty cheap compared to them.

Houston Remodeler 02-17-2015 06:57 PM

Before we get too far - Have you checked the slab in the basement ?

I someone installed a post in my his first house and after a few weeks the posts went right through the thin slab. :x:

Motordoctor 02-17-2015 10:15 PM

Yeah, I considered that too, going to look for concrete piers like they use for decking. If I can't find those, I guess I will have to make some forms and pour them myself.

Motordoctor 02-19-2015 03:46 PM

4 Attachment(s)
More dumb questions from the peanut gallery. I put some mason's string on the floor spaced 1/4 off the ends to check the flatness. Checked it under the string over each plank. As it sits, the sub-floor varies a maximum of 1/4" on a couple of planks, most of it is 1/8" or less. My questions:

Is that enough to affect the underlayment 5/8" plywood I'm going to screw/glue over the planks? Or will the plywood and the subfloor come to an understanding about how flat to be? Will the screws suck up the low spots to the bottom of the plywood without creating a low spot on the top? Never measured a piece of plywood for flatness/thickness variance so I don't know if I'm being a little too anal here.

There is some "lippage" on the planks in a few spots which I could take a belt sander to and knock it down to match the adjoining plank. Needed or?

If the answer is "get it as flat as possible before you screw it down", what would I use to take up the low spots? Have to be something about 1/8 thick compressed in 7" wide strips.

I'm planning on using Loctite PL Premium construction adhesive under the plywood. Only thing HD had in the large tube size. That OK?

Under the Hardibacker board, recommended thinset? Their data sheet says modified or unmodified. The Bostik rep I talked to say their Reflex thinset would be good but @ $35/bag it's a little pricey. I thought I read somewhere on here that under the CBU it really didn't matter and it was a waste of money putting high priced thinset.

Putting down the CBU, screws or nails? I have access to a nailgun if I need it. Would speed things up I bet.

Thanks again.

cx 02-19-2015 05:23 PM

Dan, if some of those boards are cupped a bit, making high ridges on the outer edges, I'd likely use a 36-grit belt sander on those places and any similar protrusions. Otherwise, you'll pretty much wannna put your plywood over what you've got and screw it down really well. I would not recommend using any kind of construction adhesive between the board and your new plywood.

Once your new subflooring is installed you can check for flatness and determine what more, if anything, needs to be done.

Home Depot sells CustomBlend thinset mortar, the lowest rung on their product ladder, and bedding CBU in floor installations is one of the few applications for which most of us would ever recommend it.

Any salesman who would recommend thirty-dollar-a-bag thinset mortar for bedding CBU is someone I'd recommend crossing off your list of people from whom ever to seek tile installation advice.

The purpose of the mortar under the CBU panels is not to bond it to the subfloor, but to provide a 100 percent footprint for the panels. The mortar holds them up, the mechanical fasteners hold them down.

I would recommend screws for fastening the CBU panels.

My opinion; worth price charged.

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