t1-11 plywood ? for floor material ???

[rustytoolss]

With all the concern about plywood not holding up to water/moisture/rain etc. What about using T111 exterior plywood siding for the floor ? Most T111 siding that I've seen has held up very well. I know that having the grooves cut into the plywood may not be the best thing. But I'm thinking that the bottom could have the solid surface. And the interior surface could have the grooved side. The grooves could be filled in with some type of filler (bondo?).
Or a top layer of 1/4" plywood.
I really do not know the price differences in T111 and good plywood.

[GPW]

But isn’t that ’treated’ ... Poisonous ???

[rustytoolss]

I do not know, I'll check into that.

[rustytoolss]

Just checked lowes and HD. Both said T1-11 was untreated. Lowes said limited lifetime warranty. HD said no warranty.

[MtnDon]

Exterior grade simply means that waterproof adhesives were used. You can buy exterior grade smooth face plywood and avoid all the issues about filling the grooves and dealing with the rough finish of the grooved side. The only difference between a sheet of T1-11 and plain exterior plywood is the grooved and rough sawn appearance of the side that is to face outwards on a building.

[Nobody]

Whan I build my TD in 2006 I used 1/2" CDX atop a 2x2" (actually 1 1/2x1 1/2" ripped 2x4s) framework. I covered the underside of the floor assembly with the black, sticky, roof/post asphalt coating, then placed 1" Dow 'blueboard' styrofoam in the 'voids' on the underside of the floor. 10yrs & near 30K miles in every kind of weather (sun, snow, sleet, heavy rain) & most every kind of road/terrain the floor is still as solid as the day it was built. In June 2010 on the way to Cloudcroft, NM for a gathering, we drove thru flooded streets in Hobbs, NM & several other towns. So much so that my wheel bearings 'took on water' & needed replacement/repacking when I got home. The floor withstood all that except the 1.5" high wheel wells seams separated & the TD took on water & wet our bedding. New seals at the seams cured that problem 'til the TD was rear ended later that year, causing considerable damage to the HF chassis but no damage to the floor except the wheel well seams opened again. That was an easy fix (the wheel wells, not the HF chassis, that was harder). That was 6yrs ago & the floor exhibits NO deterioration. As for road damage to the Dow blueboard, it still looks very good & shows little or no damage from road debris. Pic # 5 was made within the last year or so...

[Andrew Herrick]

Some good advice in this thread. If you can bear a little math, here's another reason to avoid T1-11 siding ...

You probably won't find siding in 3/4" (23/32) thickness, like a standard subfloor. Instead, it will be 5/8" (19/32) at best. Doesn't sound like a big difference, right? Well, it is :/ It'll have almost twice as much bending stress and twice the deflection. In other words, now your floor is half as strong. And that doesn't even factor in the grooves, which makes the situation worse

Especially if you're planning a kit trailer build, where the cross members are 24 inches apart, I wouldn't go with 5/8" anything! I know a lot of builders use 1/2-inch or 5/8-inch flooring, but I figure, with all the money you're pouring into this thing, why not build a little extra "oomph" into where it counts: the floor!

[Fenlason]

I would look at Advantech. It comes as sheathing and flooring, and it greatly repels water.

[rustytoolss]

I would look at Advantech. It comes as sheathing and flooring, and it greatly repels water.

Who sells that ?

[Andrew Herrick]

I would look at Advantech. It comes as sheathing and flooring, and it greatly repels water.

Who sells that ?

Usually available at the big box stores (Home Depot, Lowes, Menards, etc. ) It's usually sold as a 3/4-inch (23/32) tongue n' groove OSB subflooring. It's made in other thicknesses, like 1-1/8-inch, but those are harder to find. If you can't find it at a big box store, it's REALLY popular with portable building manufacturers.

[booyah]

Especially if you're planning a kit trailer build, where the cross members are 24 inches apart, I wouldn't go with 5/8" anything! I know a lot of builders use 1/2-inch or 5/8-inch flooring, but I figure, with all the money you're pouring into this thing, why not build a little extra "oomph" into where it counts: the floor!

So fun fact

I have the norther tool chassis, I have 2x2 frame build up same as Nobody, but my floor is 1/2" 5ply CDX. Floor is as solid as anything. Never any flex when in use. I did that to reduce weight.

Side walls are 3/8" lined with 1x2s, and and insulated with 3/4" R5 foam board. interior walls are 1/4" luaun plywood. ceiling is 1/8th birch outside, and inside with 1x2s and 3/4" insulation between.

Two years and about 5k miles so far and no issues with it at all.

No idea on the t1-11 stuff, but my 1/2" has been solid as all get out.

[Andrew Herrick]

Especially if you're planning a kit trailer build, where the cross members are 24 inches apart, I wouldn't go with 5/8" anything! I know a lot of builders use 1/2-inch or 5/8-inch flooring, but I figure, with all the money you're pouring into this thing, why not build a little extra "oomph" into where it counts: the floor!

So fun fact

I have the norther tool chassis, I have 2x2 frame build up same as Nobody, but my floor is 1/2" 5ply CDX. Floor is as solid as anything. Never any flex when in use. I did that to reduce weight.

Side walls are 3/8" lined with 1x2s, and and insulated with 3/4" R5 foam board. interior walls are 1/4" luaun plywood. ceiling is 1/8th birch outside, and inside with 1x2s and 3/4" insulation between.

Two years and about 5k miles so far and no issues with it at all.

No idea on the t1-11 stuff, but my 1/2" has been solid as all get out.

Obviously, using 1/2-inch or 5/8-inch flooring isn't a deal breaker Thanks for your input! And I'm glad it's worked for you! I'm trying to think 20-25 years down the line. For the extra $15-$20 to upgrade to 3/4-inch, you get a floor that's exponentially stronger and stiffer, especially if you use tongue n' groove subflooring. It's like a factor of safety. It does add about 25 pounds to your build, though.

Your walls and ceiling sound very robust, but that's because they have those 1x2's adding that extra depth, see? That's what I'm after with the floor.

One of the reasons why 1/2-inch floor "works" in teardrops is because we usually don't load them up with anything heavier than our bodies. And if you're comfortable with that limitation, then your choice of wood will certainly work. But for an extra $25 and 25 pounds, I can get a floor that I never have to worry about, no matter who's inside, what I'm hauling or what sort of roads I'm driving on. Just my $0.02. But seriously, thanks for the comment! Great to share ideas.

[Fenlason]

I would look at Advantech. It comes as sheathing and flooring, and it greatly repels water.

Who sells that ?

I get it from my local lumber yard.

[bobhenry]

Advantech is part of the zip panel family of engineered woods. I can not say enough good things about their products. I have some cut off scraps 3' x 4' I have had laying in the weather in my flat bed trailer since march and there is no swelling and no degradation of the osb portion of the product. What ever the binder is, it is bullet proof when it comes to weather.