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Anything better than plywood for floor?

UTCoyote
Explorer
Explorer
Tackling a "soft spot" in the bathroom project...

I've got the bathroom floor all out. The sub floor was 1/2" plywood.

Is there a better/best type of sub floor material to use, other than simply replacing with the same plywood that was there before? As in, more moisture resistant and or stronger?

Figure as long as I'm doing it, and I only need one sheet of material, if there is something better to use, I may as well use it.

BTW... Pretty sure I've got the source of the leaks - from above and a plumbing leak hidden under the tub - fixed already.

Thank!

- Coyote
23 REPLIES 23

spadoctor
Explorer
Explorer
Don,t waste your money use exterior grade sheathing but 4 layer not 3. If your bath did not have excessive exposure to water....much more tha is normal...you would not have to be doing a repair. What brand rig do you have that has 1/2 in plywood I'm curious. Only one I know of is Open Range.

Empty_Nest__Soo
Explorer
Explorer
LarryJM wrote:
Passin Thru wrote:
Marine grade plywood won't rot.


I don't know where you come up with such an outlandish statement, but you are 100% WRONG. Marine grade plywood has no additional treatments to prevent decay/rot CLICKY.

For the OP I agree either MDO, HDO or pressure treated could be options with the first probably the best overall.

Larry

Not only does marine plywood have no added treatments for rot resistance, it is often made with exotic tropical hardwoods which are chosen for light weight or for appearance (when used with a clear finish such as varnish), not chosen for rot resistance.

As for wood species used, the best you can hope for in terms of rot resistance when walking in and buying marine plywood is Douglas fir. Douglas fir is the same wood that you can expect to buy with good quality A-B plywood. The old growth Doug fir was only moderately rot resistant; the stuff being harvested today, not so much.

Many of the tropical species used in marine plywood actually have low rot resistance. They are manufactured with an eye on other qualities desired in boatbuilding, and they depend upon proper design and proper maintenance to prevent rot.

Save your money and get a sheet of MDO.

Wayne
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LarryJM
Explorer II
Explorer II
Passin Thru wrote:
Marine grade plywood won't rot.


I don't know where you come up with such an outlandish statement, but you are 100% WRONG. Marine grade plywood has no additional treatments to prevent decay/rot CLICKY.

For the OP I agree either MDO, HDO or pressure treated could be options with the first probably the best overall.

Larry
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Passin_Thru
Explorer
Explorer
Marine grade plywood won't rot.

mosseater
Explorer II
Explorer II
I thought Advantech came in various thicknesses? Looks like good stuff but don't have any experience with it. Pretty salty to buy, but you're not going to need a bunch of it.
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GrandpaKip
Explorer II
Explorer II
Another vote for MDO, if you can get it. Next is a true marine grade, then AC or BC.
Good luck.
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myredracer
Explorer II
Explorer II
I used marine grade plywood for a deck on a car trailer once. Only lasted a few years before it disintegrated, rotted and fell apart. Pretty disappointing at the time.

Empty Nest, Soon wrote:
Pangaea Ron wrote:
SprinklerMan wrote:
I got some old signs from a sign shop , 5 x 8 sheets , yes 5 x 8 , this plywood is for outdoor signs . The guy sells the old signs for 5 bucks a piece . These sat out in the weather for 4 years and not a bit of rot at all . Go to your local sign shop see if you can find some


Use that, it's probably MDO (Medium Density Overlay) plywood.

Yes, MDO plywood is what you want.

As a boatbuilder, I can tell you that marine plywood is so graded because of the greater number of plies used and the absence of voids in internal plies. It is not usually rot-resistant wood -- it depends on the building techniques and barrier coatings to keep it from rotting.

MDO is a better choice for your job.

Wayne

Empty_Nest__Soo
Explorer
Explorer
Pangaea Ron wrote:
SprinklerMan wrote:
I got some old signs from a sign shop , 5 x 8 sheets , yes 5 x 8 , this plywood is for outdoor signs . The guy sells the old signs for 5 bucks a piece . These sat out in the weather for 4 years and not a bit of rot at all . Go to your local sign shop see if you can find some


Use that, it's probably MDO (Medium Density Overlay) plywood.

Yes, MDO plywood is what you want.

As a boatbuilder, I can tell you that marine plywood is so graded because of the greater number of plies used and the absence of voids in internal plies. It is not usually rot-resistant wood -- it depends on the building techniques and barrier coatings to keep it from rotting.

MDO is a better choice for your job.

Wayne
Wayne & Michelle

1997 Safari Sahara 3540

myredracer
Explorer II
Explorer II
I wouldn't use any type of pressure treated wood product either. You have to use nails and screws that are compatible with it. And if it's sitting on top of steel or aluminum joists or frame parts, you're likely to get corrosion.

I would go with a better grade plywood. Marine might be good but I don't think necessary and there's other choices. Go to a plywood specialty store if you have one nearby. Why did you have a subfloor problem to start with?

If the joists are spaced too far apart, you could try either thicker plywood or add some bracing under it like angle iron or 2x lumber on the flat. Not sure how you plan to put it back in, but I would use construction adhesive for overlapping joints or wood bracing. If you have access from below, you could double-layer the plywood and use adhesive.

If you don't have access and if there's no obstructions below, you could cut a couple of pieces of plywood about 1-2" oversized all around then cut it in half. Then feed each piece in and glue it and screw from the top. Then add the final patch piece. If too many obstructions below, cut strips of plywood say 2-4" wide and put them under the floor to support the final patch piece and screw & glue.

nomad297
Explorer
Explorer
carpetguy2 wrote:
I wouldn't use treated sub floor if you plan on putting any type of flooring down.Unless it has been dried out for awhile. Holds alot of moisture in it.from being treated


Yup
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carpetguy2
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Explorer
I wouldn't use treated sub floor if you plan on putting any type of flooring down.Unless it has been dried out for awhile. Holds alot of moisture in it.from being treated
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UTCoyote
Explorer
Explorer
Thanks for the idea folks, I appreciate it.

Looks like marine grade plywood is what I'm going to go with. I wish I could step up to 3/4", or even 5/8", but it needs to have linoleum transition smoothly to the rest of the floor that is not being replaced. Needs to fit under existing walls, cabinetry etc. too, so sticking with 1/2" it will have to be.

- Coyote

Dog_Folks
Explorer
Explorer
Marine grade plywood. Step up to 3/4"if you an. I did and am very happy with it.
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westend
Explorer
Explorer
Marine grade plywood AB, in my area the good glass filled stuff is $125/ 4'X 8', in 1/2".

An alternative is span rated OSB or exterior plywood BCX and seal it. Either one is serviceable for RV floors. I seal both sides/edges and make sure the sealant is OK with any glue application if retrofitting vinyl sheet goods as a finished floor. This means an acrylic sealer.
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