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Unread 01-05-2016, 05:13 PM   #1
longr27
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Seeking hope/advice - failed deflection for bathroom tile install

First time poster hoping to get some advice on a bathroom tile install job. Was planning to replace floor tile in our small main bathroom with a small porcelain hexagon tile. Ran specs in the deflectolator (to the best of my knowledge) and failed miserably with a result of L/243, apparently meaning any tile is out of the question.

Specs:
Wood: S-P-F (so I chose 'unknown wood in good condition')
2x10
16" o.c. spacing
15 feet long between supports

We live in a 1 story ranch with the bathroom situated over the main center beam of the house, about half of the bathroom square footage lies on either side of the beam (pretty small bathroom). The subfloor looks to be 42/20 C-D (which I'm assuming from what I've read is not the best).

Wondering if I have any options at all in the way of being able to tile. Any advice is greatly appreciated! Reference pictures attached.
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Unread 01-05-2016, 05:38 PM   #2
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Welcome, Rachael.

Given the stamp on your lumber, I can find you a span table that says it would meet L/360 deflection minimums by your description. That's the minimum requirement for building code and for the ceramic tile industry. For remodel work, I much prefer our Deflectometer, but that's up to you to decide.

The biggest problem you have is the bathroom location. When you have a live load in the center of one of those two joist spans, you'll get movement at the end of the joist where it crosses that support beam that has a tremendous force. Not a lot of travel, but a whole lot of force. If the two joist ends are well fastened to each other in that area, that would at least be somewhat helpful.

What is the thickness of your subflooring? Does it have T&G edges?

You're correct that is is not of a grade suitable for a ceramic tile installation, but if it's at least nominal 5/8ths" and T&G, you could add another layer of nominal half-inch plywood and be in pretty good shape. That would also help with the uplift forces over that support beam.

My opinion; worth price charged.
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Unread 01-05-2016, 07:25 PM   #3
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Agree with CX on the need to tie those beam sections together. I'd recomend through bolting the beam together with four 1/2 bolts; two staggered on each side of the joint.
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Unread 01-05-2016, 08:53 PM   #4
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That notched joist at the shower drain needs to be remedied. It appears to be notched about half way thru. Sliding in another joist as close as possible to the existing may take care of it... depending on the thickness of the plywood.

Let us know if that's possible and how far away from existing joist it would end up, along with ply thickness. For now, don't remove existing notched joist.
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Unread 01-05-2016, 09:11 PM   #5
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Looks like that support beam could use some work too. Perhaps some carriage bolts, washers and nuts.
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Unread 01-05-2016, 10:06 PM   #6
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Thanks for the great and fast responses!

The plywood subfloor seems to be only 1/2" actual thickness with cement board layer on top and thinner layer of plywood on top of that (sorry if that layer has an actual name - I have no idea). Can't tell if the floors are tongue and groove, is there a relatively easy way to determine that?

The joists seem only to be secured to each other with a number of nails at the end of each joist. So adding some bolts would be easy enough to do.

Ha! I was waiting for the huge notch in the joist under the shower to be mentioned. I also noticed this when taking measurements to plug into the deflectometer. If we added a joist, there would just be about 3/4" of space between the notched joist and the new joist. Another thing to add to the list!

I should also mention we need to remove and replace the subfloor around the toilet anyway, as there had been a previous leak apparently and that section of the floor is pretty rotted (the main reason for this whole project).

Here's a cross-section of the floor layers:
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Unread 01-05-2016, 10:36 PM   #7
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Quote:
Originally Posted by Rachel
If we added a joist, there would just be about 3/4" of space between the notched joist and the new joist.
That's good news as you can fill the space with plywood. Glue and screw the entire joist as one lamination.
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Unread 01-05-2016, 10:38 PM   #8
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I'd lose the top layer of plywood and the cement board below it. You'll find out quick if the bottom layer is tongue and groove at that time, since the edges of the sheets will deflect separately when you step on them.

If it is tongue and groove, I would add a layer of 1/2" plywood with a face grade of A, B, or C, properly installed. Then follow that with a tile membrane or cement backer, and tile.

I see the plywood below the cement board, but is that a joist below it, or something else?
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Unread 01-06-2016, 12:39 AM   #9
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That 42/20 stamp on the ply may be an older version of 5/8 nominal, which would measure something less than 5/8". Still no good for a floor without going over it with another layer of ply as noted.
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Unread 01-06-2016, 05:52 PM   #10
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Glad to know the notched joist is a relatively easy fix.

Kevin - the layer you see below the plywood is just a temporary patch we installed from the basement to cover that hole to keep cold air from coming up from the basement. For some odd reason when we bought the house that hole (about 2" diameter) was drilled directly through the tile and all layers of the subfloor, so there was just a random open hole into the basement..


What would you all recommend if, worst case scenario, we do remove the top 2 layers and discover that the initial layer is not tongue and groove. Can T&G be installed over that layer or would it all need to come out and T&G be installed directly over the joists?

Also, in doing all of this, we weren't planning to rip out the shower stall. Is leaving it untouched a possibility with the adjustments that need to be made to the floor?
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Unread 01-06-2016, 06:46 PM   #11
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If your first layer of subflooring is not T&G, you'll need to provide blocking under the between-joist seams.

Unless it's really only 1/2" thick, in which case I'd advise removing it all together and starting over with a minimum nominal 3/4" T&G material.

My opinion; worth price charged.
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Unread 01-06-2016, 11:00 PM   #12
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Quote:
Originally Posted by Rachael
Also, in doing all of this, we weren't planning to rip out the shower stall. Is leaving it untouched a possibility with the adjustments that need to be made to the floor?
You can leave it. If it's installed properly, then just be careful working around it so as not to disturb it. Leave about a 1/4" gap between plywood or backer board & the base, then fill these with polyurethane sealant. Then leave a grout joint width gap in the tile, about 1/8-1/4 minimum, and fill with silicone - color matched to the grout.
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