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Water leakage in small bathroom with 2x8 subfloor


Michael_G's Avatar
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03-08-16, 10:58 PM   #1  
Water leakage in small bathroom with 2x8 subfloor

It seems that 2x8 sub-flooring isn't something people talk about much in the these forums.
I was replacing the tile in a small 5x8 full bath when I noticed my toilet decided to leak. I pulled up the pressboard underlayment to notice some water damage in the subfloor. A section about 3x3' was very wet and some sections of the boards were very soft. I also noticed the hole about 2x4". Attempting to dry it out, I put some work lights on the area. I might have made a slight mistake because the area started to get some slight warping in those 2x8's. Now I'm at the point where I'm wondering what to do. The warping is slight (about 2 mm hight diff) and is where the toilet will sit so no one will be walking on it. I don't want to half ass this but at the same time I'd rather put as little money and effort into this as possible.
Check out some of the pics for a better idea of what I'm up against.Name:  Hole-in-bathroom-floor.jpg
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Size:  50.1 KBName:  Bathroom_Floor.jpg
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Appreciate the suggestions in advance,
Michael

 
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03-09-16, 02:55 AM   #2  
Well, to begin with all the particle board has to be pulled up and disposed of. Then you have a clear view of the framing and can correct any problems before you apply a new subfloor, usually Advantech. You say the subfloor is 2x8. What is the joist spacing and what is the longest unsupported span in that space?

 
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03-09-16, 03:59 AM   #3  
2 X 8's are talked about all the tile in the tile section.
Main reason, unless it's a really short span there not strong enough on there own to support tile unless there's some added support when laying tile.
If that was my floor I'd start by removing all that old subflooring right up to the walls.
That way it's far easier to work on the joist and you'll end up with a flatter surface to work off of with the new subfloor.

 
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03-09-16, 08:48 AM   #4  
OK, we know you have 2x8 joists - what's the spacing and unsupported span?

 
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03-09-16, 02:55 PM   #5  
You can not tile over a 2x8 subfloor - buy subfloor, you should mean 2x8's laying flat and attached to floor joists. If that is what you are describing, dimensional lumber has too much expansion and contraction to act as a stable platform for tile. You must introduce a layer of more stable plywood or OSB subflooring to build your base for tile. Minimum 1/2" plywood or 3/4" OSB would be in order. Then cement backer board, then tile.

Don't forget to answer other questions about the size, spacing and unsupported span of the floor joints themselves.

 
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03-09-16, 02:58 PM   #6  
Z, I don't think he has 2x8 subfloor, but instead particle board. The 2x8's are the joist sizing. Now, I did build a log home once with heart pine T&G 2x8 rail road box car flooring. I'd put a tank on that.

 
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03-09-16, 03:44 PM   #7  
Looks like a flat 2x8 subfloor to me... (more common in the Pacific NW) with probably 5/8" particle board underlayment on top of that. I would think getting rid of all the particle board is obvious... and if the 2x8s are largely ok, the hole isnt that big of a deal provided you are putting 3/4" t&g Advantech over it... then cement board. We will stay tuned for more info on the joists.

 
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03-09-16, 03:54 PM   #8  
I do believe y'all are right. I didn't get past the ugly of the particle board. Agree, Brant.

 
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03-09-16, 06:26 PM   #9  
You can see the particle board is removed and remnants of the felt paper and then distinct uiform striations of 2x8 planks in the second picture. Either way, you can not tile directly on that without a buffer of ply/OSB to stabilize.

 
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03-10-16, 07:53 AM   #10  
Thanks for all of your responses.
It appears I gave the wrong impression when I said I was replacing the tile. I'm actually just replacing it with vinyl. Not all of the pressboard was wet but I'm guessing you're all suggesting that I just remove it and replace the entire area's underlayment.
As far as using "Advantech", is there some advantage of this over plywood? Again, I don't want to do this half-assed but I'm selling the house and my local big box stores don't carry this product so tracking it down seems like more work than it's worth.
I will find out where the joists are tonight. If they are under the tub or under the vanity, I assume I'm going to have to insert a box to support that area. If so, I assume I can just make that out of 2x4's. That's, at least, what I've seen others online do BUT they also didn't have 2x8's planks as the sub-floor.

 
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03-10-16, 04:11 PM   #11  
Advantec is stronger, no voids, more water resistant, comes with a 50 year warranty.
Any Home Depot, local lumber yard or Lowes in my area carry's it.
No clue what you mean by building a box around a tub or vanity.
The tub can stay in place the subfloor gets cut out with a toe kick saw.
Unless it's a built in vanity it also come out to lay the new sub flooring.

 
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03-10-16, 06:31 PM   #12  
I think HD carries it in the brand name of Home Advantage

 
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03-10-16, 06:52 PM   #13  
No clue what you mean by building a box around a tub
I'm sure he is talking about if the joists go in the direction of the tub then there is no nailing surface for a new subfloor.

If you are going with vinyl, you need only repair the damaged floor with new 2x8's and then cover all with a underlayment grade 1/4" plywood (not luan) and skim any nail holes and seams. Must be super flat and smooth for vinyl.

 
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03-12-16, 12:02 PM   #14  
Unless it's a built in vanity it also come out to lay the new sub flooring.
I just put a granite countertop on that vanity. Pulling that thing off is going to be a nightmare.


Home Depot, local lumber yard or Lowes in my area carry's it.
Unfortunately, HD and Lowes don't seem to carry it in western Washington. I'll have to check some of the other non-big box lumber yards. The current underlayment is 5/8th.


I'm sure he is talking about if the joists go in the direction of the tub then there is no nailing surface for a new subfloor
Correct. I was under the impression that was called a "box" but I'll go back and confirm that.


Now, would it be "bad" to cut out the rot around that hole and replace it with a block of good wood? I'm thinking screwing/"liquid nail" it in there. It seems that after every dried out, there is only that small hole that's bad. I cut out a bit of it and it's good wood.
For the slight warping, sand it down or use some floor leveling compound. The greatest dip down is 3/16".

I feel like I'm getting into that area of "doing it wrong" but I'm down to one bathroom with three women in the house and just trying to get this bathroom put back together so that I can move onto the rest of the house.

 
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03-12-16, 12:44 PM   #15  
A rule of thumb is to remove wood so that the patch touches at least 3 floor joists. That would be optimal if you can. Then cover with your 1/4" underlayment and then your vinyl.

 
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