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Old 04-10-2009, 07:21 PM   #1
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Evaluating my subfloor before laying tile


Hello all,

I recently had all new joists and a new subfloor put into a bathroom as part of a (very full scale) bath remodel. I still have an access hole from the top and I want to make sure everything is in good order before sealing up the subfloor and putting down backer board.

Details:

1) old porch walled up many years to make a room
2) the house: brick on brick construction, poured foundation; the bathroom: bandboard 2x10s around the perimeter, sitting on two concrete piers about 30" off the dirt floor
3) room is approximately 10' x 5.5'

Due to termite damage, the bandboards got new 2x10s either sistered on, or replacing existing boards that were too damaged to use.

I have 5 new 2x10x10 joists in the space. They are all sitting in joist hangers. They are all 16" OC, except for one small offset, which was done to accomodate a 3" toilet drain.

There is no bracing between the joists, unless you count the few boards thrown in by the plumbers to hang their pipes on.

The joist attached to the exterior of the house is held in place with Tapcons.

The subfloor is 3/4" Sturd-I-Floor OSB, nailed and glued in place (probably 8D nails).

My questions:

1) does the joist attached the house need any additional bracing underneath it, or are the Tacpcons sufficient?

2) do I need any bracing between the joists?

3) should I screw down the subfloor or are the nails and glue sufficient?

4) anything else?

Thanks in advance. I am "just" a DIYer, but I believe in doing things right the first time, so I can fix it and forget it. I don't want to cut corners to save a couple of bucks or a few minutes. So if you have suggestions, let's hear 'em.

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Old 04-11-2009, 10:52 AM   #2
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Evaluating my subfloor before laying tile


If possible put a few through bolts into the foundation wall to better support the band joist. For tile you want a minimum sub floor 1 1/8" thick so add another exterior grade 1/2" plywood. Leave 1/8" gaps all around and over lap the seams by at least 24" past the existing 3/4" plywood. Screws and glue are best. Use either Ditra or 1/4" cement backer board and thinset to set the tiles. Add blocking between the joists to reduce twisting of the joists.

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Old 04-11-2009, 01:36 PM   #3
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Evaluating my subfloor before laying tile


How big are the piers? The latest is not to use CDX ply because of the air pockets in that grade. It is not approved for floors. Another exterior grade is fine, as Bob said. Good read:

http://www.johnbridge.com/vbulletin/...ad.php?t=38913 Be safe, GBAR
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Old 04-11-2009, 10:20 PM   #4
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Evaluating my subfloor before laying tile


I have no idea why you need 1 1/8" of subfloor for tile. New houses have 5/8 or 3/4 inch subfloor ,ditra, then tile. A 2x10 is going to have VERY little flex over 10 feet. I would maybe put a few screws in the floor and add something other than tapcons. maybe a few concrete anchor bolts. If you want to be extra safe you could add some bridging midway between the joists.
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Old 04-12-2009, 01:29 AM   #5
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Evaluating my subfloor before laying tile


Quote:
Originally Posted by GBAR in WA View Post
How big are the piers?
Not sure of the dimensions and they're covered in insulation now, but here are some pix:



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Old 05-21-2009, 03:06 AM   #6
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Evaluating my subfloor before laying tile


I took a few pics of the joist that is right above the foundation.



I thought it was going into the foundation, but it's actually going into the brick with Tapcons.

Is this sufficient? The house is brick on brick construction, and there is another joist on the other side of those bricks - around the perimeter of the basement. Would it be overkill to go through both layers of brick and fasten those two joists together with some long bolts?

Given the short span (10') and the width to depth ratio of the joists (1:5), I'm assuming that cross bracing would be unnecessary.

One last question - if I have 10 mil poly down in this crawlspace, is pea gravel going to buy me anything?

Thanks again.
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Old 05-22-2009, 12:39 PM   #7
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Evaluating my subfloor before laying tile


Patrick, my assumption is that the band joist with the tapcons into the brick is serving as a ledger that the edge of the subfloor sits on and that other than the floor sheathing it doesn't have other loads from the walls above. Correct?

If so, that's the only thing that makes me feel good about the installation. If all you're supporting is the floor sheathing it'll probably be fine. Tapcons are certainly not enough to do the job if that joist serves as anything more than a nailer for the floor sheathing. Although the best idea would be to have an engineer come by and make recommendations, my only suggestion would be to consider beefing that joist's support up a little bit just as a little insurance. Tapcons into brick are good for holding little things like hose reels and mailboxes up but structural fastening into brick isn't all that reliable unless some really professional measures are taken. Instead, a 2x6 treated ledger strip could be bolted to the concrete foundation wall right below and tight to the 2x10 ledger supported to the brick. 1/2"x6" wedge anchors could be drilled into the concrete every foot or so to properly anchor the ledger to it. The 2x6 (and thereby the foundation wall) would then physically support the loads exerted on the brick. You might have to so some carving on the ledger to get it tight to the wall.

As for the floor sheathing discussion...
3/4" T&G sheathing and 16"oc joists is just fine for most ceramic tile provided the joists aren't overspanned. 5/8" would be insufficient for a good tile job in my professional opinion. 1-1/8" (they used to call that 2-for-1 and use 5/8" and 1/2") would be even better and would be what you'd probably be safer using for stone tile like slate or travertine. Remember that the 1/4" wonderboard (or Ditra if you're using that) offers NO structural strength or stiffness to the floor although it is definitely necessary.
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Old 05-22-2009, 12:41 PM   #8
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Evaluating my subfloor before laying tile


Quote:
Originally Posted by pmoe View Post
One last question - if I have 10 mil poly down in this crawlspace, is pea gravel going to buy me anything?
The poly needs to be secured, so some gravel on top of the poly is how it is usually done. I'd be sure to have gravel under it as well though.
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Old 05-22-2009, 01:10 PM   #9
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Evaluating my subfloor before laying tile


In the picture is a nail through the decking into and out of the joist. It will squeak. Pound it back up with a punch or ?.

Don't forget to insulate with a kraft facing towards living space.

Taking short-cuts on the layers of ply, at least bridge block the floor, to distribute the loads.

Two, little 12"x12" piers are not enough to support the new bath. Could you pour some more?
The tapcon joist is toe-nailed at each end? Could you pour a pier in the middle span at outside wall? Then beam, or dbl joist under the middle of joists, from pier to old concrete wall with a masonry beam hanger.

http://www.strongtie.com/products/co...UM_MASONRY.asp Be safe, G
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Old 05-23-2009, 11:47 AM   #10
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Evaluating my subfloor before laying tile


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Originally Posted by thekctermite View Post
If all you're supporting is the floor sheathing it'll probably be fine. Tapcons are certainly not enough to do the job if that joist serves as anything more than a nailer for the floor sheathing.
It's only doing a bit more than holding up the floor sheathing.

The wall on the exterior of the house was plaster on brick. When the rest of the bathroom was being partially framed, I had them build a wall on top of that wall, like so:



The roof joists are attached to an existing ledger board as well as the new wall. Those joists are now supporting a 3/4" TnG beadboard ceiling.

Does this change your recommendation?
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Old 05-23-2009, 11:48 AM   #11
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Evaluating my subfloor before laying tile


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The poly needs to be secured, so some gravel on top of the poly is how it is usually done. I'd be sure to have gravel under it as well though.
I can't resist - why do you need the gravel under the poly?
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Old 05-24-2009, 12:47 AM   #12
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Evaluating my subfloor before laying tile


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I can't resist - why do you need the gravel under the poly?
Nothing says you have to do it that way. Gravel facilitates movement of moisture, soil doesn't necessarily do that. Personally I'd rather have a little gravel and some air under the poly instead of just wet dirt (read: condensation) all the time. Just a suggestion, not a requirement.
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Old 05-24-2009, 07:55 AM   #13
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Evaluating my subfloor before laying tile


In the last pic you posted, there is nothing to nail the baseboard too on the far side. You should add another piece of blocking.
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Old 05-25-2009, 03:15 AM   #14
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Evaluating my subfloor before laying tile


Quote:
Originally Posted by GBAR in WA View Post
Two, little 12"x12" piers are not enough to support the new bath. Could you pour some more?
Not easily. I'm not sure of the exact dimensions of the piers, but they are closer to 15" or 16" square, and I assume they are original to the house (~95 years old).

I made a quick, not to scale sketch of the bath in Visio so this may be a bit easier to visualize.




Quote:
The tapcon joist is toe-nailed at each end? Could you pour a pier in the middle span at outside wall? Then beam, or dbl joist under the middle of joists, from pier to old concrete wall with a masonry beam hanger.
I actually don't know or don't remember how the band joist is fastened at the ends, and the ends are all buried under spray foam insulation now.

Pouring a pier at this point would be nigh impossible given that most of the subfloor is in place and the outside walls are vinyl siding over the original siding.

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