4x6 Joists on 48" centers [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

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Val Brown
08-07-2004, 08:50 PM
Hi, great site you have here. I'm just browsing all of the catagories trying to find some similar questions but as yet have not found anyone with a similar subfloor. The house is about 30 yrs old and has 4x6 DF joists on 48" centers. The subfloor consists of 2x8 T&G DF with 5/8" particleboard underlayment except the bathrooms where they used 5/8 plywood underlayment over the 2x8 T&G.

We want to tile the kitchen, hall and one bathroom. The floor "feels solid" but I have resigned myself to either using 4x6's on new piers in the center of the 48" joist spans OR using hangers and using 2x6's on 16" centers under the areas that we want to tile. The 5/8 particleboard is covered with linoleum. We are going to put 1/4 inch Hardibacker over that.

Thanks for any comments and or suggestions.
val brown

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cx
08-07-2004, 09:32 PM
Welcome, Val. :)

Actually, there are a gaggle of threads out there on that same floor construction. Only thing we need to know is the spacing of the piers or other supports under the 4x6 beams.

If you really have particle board over that subfloor, it's gotta go. Your subfloor (the T&G 2x8s) is fine so long as you install a minimum of 3/8ths inch exterior-glue plywood, with a grade of C or better on each side, over it. You can install CBU over that and you're fine for ceramic tile.

Did I mention no particle board?

And we don't generally recommend installing over vinyl, especially cushioned vinyl, especially over particle board. :shades:

You need to remove the particle board, by the way, if I didn't mention that. :)

My opinion; worth price charged.

John Bridge
08-08-2004, 10:13 AM
Welcome aboard, Val. :)

I didn't notice whether CX mentioned the particle board. It'll have to go. :D

Val Brown
08-09-2004, 08:10 PM
Thanks for your timely response CX and yours also John. You guys rock , Or tile- whatever :) I did not like to hear your insistance on the particleboard removal as the local TILE CITY guy said that linolium over particleboard plus a layer of Hardibacker would "work". Bottom line is that I took your suggestion/insistance as I want the "tile job" to last. All of the particleboard is off except for a small strip that I will finish tommorrow when I rent the small saw to get next to the cabinets.

Now if you could help with the big questions. I was under the house today and the 4x6 DF beams are supported every 5-6 feet. The beams are on 4' centers. The subfloor is 2x8 DF T&G, layed perpendicular to the beams. I plan on replacing the removed particleboard with Plywood.

WHAT thickness and grade would you all recommend that I use??? And the 1/4 Hardibacker will go on top of the plywood. The particleboard had a vapor bar between it and the T&G.

Should I replace the vapor bar when I nail down the plywood?? And the Bigger question???? Will I need to support the subfloor with additional wood?

Your calculator seems optimized for 2X wood. Perhaps it is possible to double things to calculate 4X wood. Anyway what do you think? Do I need more support between the 4' centers? If so will a 4x6 post & beam work centered between the existing 4' centers? After crawling under the house, that seems like the easiest way. Not much room to swing a hammer for 2X6 joist hangers :bang:

Thanks for helping a novice out :cool: You guys RO--- well you know your advise valued and appreciated.
Thanks
VB

cx
08-09-2004, 09:55 PM
From my earlier response:Your subfloor (the T&G 2x8s) is fine so long as you install a minimum of 3/8ths inch exterior-glue plywood, with a grade of C or better on each side, over it. You can install CBU over that and you're fine for ceramic tile. That's my story and I'm stickin' to it. :)

Now that we know your beams are properly supported, your floor structure is fine. "How do I know that?" you might axe. I know that on accounta Injineer Bob done tole me that a number of times and Injineer Bob knows on accounta that's his job. :shades: No, you can't find it in the Deflectolator.

Don't put anything under the plywood, unless you just wanna glue it. I always recommend glue for layered plywood subfloor, but I'm not entirely sure the benefit is the same over boards - on accounta Injineer Bob ain't never tole me. But for sure don't use any sort of vapor barrier; you don't want to be trapping moisture (you'll dump a whole gaggle of water on it when you lay that CBU) in the plywood layer. It was a good idea for the particle board/vinyl guy, but not for the tile guy.

And if you don't have a height problem with your finished floor, half-inch plywood flattens things out better than three-eighths.

My opinion; worth price charged.

Val Brown
08-10-2004, 07:26 PM
You made my day saying that I did not need more subfloor support :yipee:

I'll be buying 5/8 CCX tomorrow. Is there anything particular that I should be aware of in how the plywood should be layed? Should all pieces end over a 4X6? Should the plywood be at right angles to the 2X8's OR to the 4X6's? I know these are probably very novice questions and you have probably answered them before.

The Tile city guy said to use roofing nails for the Hardibacker over thinset. Is that the correct way?

Thanks AGAIN!
vb

Peggy Donahue
08-10-2004, 07:58 PM
Right angle to the 4X6.

All sheets must end on the support...and the joints must be staggered.

Full Sheet - Full Sheet - Full Sheet - piece at the end ..next strip is

Piece at end - Full sheet - Full Sheet - Full Sheet

Do you know anyone that has an air compressor? and a roofing nailer?

If not, does your budget afford the rental cost? Wait until you hear how many nails you need to put in. :crap: :crap: :crap: If I remember right...every 6 inches. :eek:

Wait for confirmation from the 'GUYS'.

Peggy Donahue
08-11-2004, 05:56 PM
Bumping up so you "Guys" can give Val a confirmation on what I said.

Right angle meaning in the opposite direction of the floor joists.

Thanks,

bbcamp
08-12-2004, 05:30 AM
Peggy remembers her training well!

Second layer of plywood doesn't have to start and end at joists. In fact, Schluter company provides instructions to offset the joints by 4 inches.

Plywood face grain should run perpendicular to joists.

Hot dipped galvanized roofing nails may be used to attach the backerboard. Don't buy the electro-plated nails, the plating flakes off easily. If you do use a pneumatic nail gun, keep lots of weight on it as you shoot in the nails, so they are driven completely home. Otherwise, use backerboard screws. And don't forget the thinset under the backerboard or to tape and mud the joints.

Peggy Donahue
08-12-2004, 07:39 PM
Hi Val - Did you get your 5/8 CCX yet? Is it down? If it is, so be it.

I started thinking about my advice and have changed my mind. I missed the fact that you have the 2x8s perpendicular to the joist. So the ply (I believe) should go perpendicular to the 2x8s (not the joists). Probably doesn't matter that much anyway. Since I was thinking about you I figured I go back to my thread and find the rest of the info you will need. Id love a sign off on all of this from JBs people.

Here's it goes:

If you've put the ply down already, jump to #4 in the middle about screws.

1. Make sure the 2x8s are secure after you pulled all that particle board up. Put in some extra screws to be sure.

2. CX wasn't sure about the construction adhesive, but I would use it. You've got 4 feet between the joists and if the 2x8s or ply have any twists, warps etc., with the adhesive and screwing the ply down you'll get everything tight together.

3. So add construction adhesive. I'd go perpendicular to the 2x8s. But it probably doesn't matter here again. Zig zags, swirls maybe?

4. Put your CCX down perpendicular to the 2x8s landing on the joists (at least that's what they had me do). bbcamp..there's no schulter products being use above the CCX so I'm not sure why the difference in advice from my job to this one. Screw down with 2" screws to the joists every 3 to 4 inches (the extra labor to do every 3 inches is courtesy of TileGuyTodd and Jay F) and 1" screws every 6 to 8 inches in the field (again extra labor-but I did it). Start at one end and work your way to the other so you press out any warps. You don't say how many sq feet your doing. Mine was 200 sq ft and I used 11 1lb boxes of screw. Grip Rite Fas'ners - Primeguard Phillips Exterior Screw (green labeled box). Maybe you can find a place that carries the 5 lb boxes.

5. 1/4 Hardibacker should not line up with the ply joints and stagger the joints of the CBU by at least 12. The CBU goes down over cheap non-modified thinset (even if the bag says to use an admix don't-its just to fill any voids) using a x 3/8 square notched trowel. Using 1 roofing nails attach the CBU to the ply using the hardibacker nailing pattern (plus some more to keep some people happy).

6. Time to tile. I used Flexbond Premium Flexible Bonding Mortar mixed with water to put down the tile using the same by 3/8 square notch trowel. Put down a couple and then pull some up to see if youre getting good coverage on the entire surface.

7. Grout is next. Don't use ad-mix. Mix it up, let it slack 10 minutes, mix again and youre in business. (Actually this goes for both of the thinsets above, also). Spread it around with the float, pulling diagonally to get it stuck in the lines. Wait until it starts to harden. When you push with your finger it moves slightly but you can feel that its hardening. It takes practice. Youll get it. Then clean the tile, smooth the grout lines and clean and clean to get all the grout off the tiles.


Best of luck,
;) ;) ;)

cx
08-12-2004, 10:16 PM
2. CX glues everything.

4. Plywood goes perpendicular to the joists, no matter what. End joints of plywood don't want to fall over the joists, and you don't want to try to screw the plywood into the joists anywhere, only screw into the board subflooring. I would screw plywood of that thickness in a schedule of about 6 inches on the edges and no closer than eight to ten in the field.

5. If the CBU manufacturer's instructions specify a type of thinset, use that type.

7. Peggy means to let your stuff, any Portland stuff, "slake" not slack. Slack is what you do while the stuff is slaking. Or you can practice your standing around, either is acceptable. :)

My opinion; worth price charged.

Davestone
08-13-2004, 06:34 AM
For the full explanation of slacking go to Flatfloor. :)

Peggy Donahue
08-13-2004, 11:06 AM
[QUOTE=cx]4. Plywood goes perpendicular to the joists, no matter what. End joints of plywood don't want to fall over the joists, and you don't want to try to screw the plywood into the joists anywhere, only screw into the board subflooring. I would screw plywood of that thickness in a schedule of about 6 inches on the edges and no closer than eight to ten in the field.

7. Peggy means to let your stuff, any Portland stuff, "slake" not slack. Slack is what you do while the stuff is slaking. Or you can practice your standing around, either is acceptable. :)

QUOTE]


cx - Hummm...seems I got some different advise :confused: :confused: . :shake:

So if you're putting two layers of ply they both go with the joists? OK - I'll just go slaking away now and keep my big yap shut. :x: :x:

John Bridge
08-14-2004, 02:57 PM
As CX says, plywood, whatever layer, always goes perpendicular to the joists. Doesn't matter what type of subfloor sheathing/decking you have. And the subfloor layer is the only one that actually butts over the joists. All subsequent layers butt a quarter-span off the joists, as Bob mentioned somewhere a ways back. ;)

So right now, the CCX goes across the joists, and the sheets butt off the joists. A quarter span of four feet is one foot.

Then that floor would be a good candidate for Schluter Ditra. It's much easier to install than back board. Takes up less space, too. ;)

cx
08-14-2004, 07:57 PM
Well, Peggy, you see my disclaimer up there, eh? ;)

But I don't need it for that one. If you are using plywood for any application in which it is providing bending strength across a span, it must have the face grain perpendicular to the supports. There are a number of other applications in which it doesn't matter, but suffice to say it's always true on floor decking.

Please to bring whomever says otherwise over to the Hangout for some discussion. :)

Peggy Donahue
08-14-2004, 11:00 PM
CX - No linching mob needed. Just an oversight during my 3 million questions. My cdx was put down correctly (which was before I found this site and even thought about tiling it). I don't know why I thought the ply build up should be perpendicular to the previous layer of ply, but that's what I said I was going to do. Got no objection.

BUT WAIT. THIS THREAD IS ABOUT VAL BROWN. and we haven't heard from her/him.

Val ... are you out there?

Mike2
08-15-2004, 08:55 AM
My cdx was put down correctly.... :uhh:

Hi Peggy, I'm hoping that was a typo...like I'm really hoping that was a typo. If its not I suspect the gentleman from Bourne will be back with more to say about what type of plywood to use, and what type never to use.

Peggy Donahue
08-15-2004, 12:46 PM
Don't worry about it Mike. They know ALL about it. :bang:

Val Brown
08-15-2004, 08:57 PM
All of you folks were having a such a fine discussion, I thought that I would just keep on pounding nails. As I read now, I have made an error that I cannot now correct. I nailed the 1/2" CCX perpendicular to the floor joists but terminated the ends on the floor joists. 1/2" was used instead of 5/8" for finished floor requirements. The house is a 30 year old rental that my wife Laura and I are remodeling for our soon tobe new tenants. I would assume that the house has pretty much settled all its going to, but also assume u pros will have some other valid reasons for not terminating underlayment on the floor joists. Be that as it may, I will just have to accept the consequenses of not waiting for a pros answer. Anyway it was all worth it finding out that I did not have to crawl under the house and beef it up :) It is nice to be able to contact people who are knowledgable and willing to help. My fault not to have looked for all the info a few days prior to needing it. Thanks for the help.
73's
N7SEA
val brown

bbcamp
08-16-2004, 05:31 AM
Val, terminating the plywood on the joists has been done for ages, so don't sweat it. The method we describe has recently been shown to be superior, but the old method hasn't been shown to be bad.

So, go worry about something else! :D