Floor build

[AKRefugee]

Hello all. I am starting my first build. It will be the Benroy style. I have my frame built and am now ready to build and attach the flooring.
I will be insulating the trailer starting with the flooring.

After reading through the directions for the flooring in Step 3 I am a bit confused. It talks about using roof tar to coat the underside of the floor and then pressing the EPS into the wet tar. This is the part that confuses me.
Every video I have watched so far looks like the EPS is not in contact with the roofing tar.

The plans also talk about screwing the EPS into the recesses with 1 1/4' SS panhead crews and fender washers. Again something I have not seen in any of the videos.

The way I "think" it should go is 1/2" plywood, 1x2 frame glued down, 1 1/4" SS crews screwed through 1x2 into the plywood (THIS WILL BE THE BOTTOM SIDE), cover plywood side only with roofing tar, after dried attach to frame. glue EPS into cavities, another layer of 1/2" plywood, screw through plywood into 1x2, patch over screws with putty, sand, seal with urethane (THIS IS NOW THE TOP SIDE or the INSIDE THE TRAILER).

Does this sound correct?

Thanks for your assistance

[saltydawg]

The easy way, but costs a little more.

!/2 inch ply coated on the outside with epoxy or the mix, thoroughly soaked and sealed on the "bottom". Then a layer of foam covered by another layer of ply, use epoxy to hold it all together. If you use 1/2 ply for both the bottom and floor and 1 inch foam you wind up very a very solid 2 inch thick floor. Depending on how your going to attached the walls you can put a 1 inch tall board that goes in 2 inches around the edge, ie make the foam 2 inches smaller on each side. You dont need a floor frame when done this way. Just finish the floor as you want after the epoxy cures.

I personally would use epoxy and seal and coat everything wood, then you have as close to a rot proof floor as possible with it being made of wood.

Some say a few coats of quality outdoor latex paint is fine too, I like epoxy. No need for the tar.

[tony.latham]

...cover plywood side only with roofing tar...

There's a reason that tar was used in the 1940's. (They used what they had.) But this is 2020. I might suggest epoxy or two or three coats of thinned oil-based polyurethane.



If I used tar, I'd be sleeping in the shop.

...is 1/2" plywood...

1/4" ply for the top and bottom skins is fine. Unneeded weight builds up during a build.

Here's my frame:



The temporary gussets are to hold the parts in place until one side can be sheathed.



Tony

[bobhenry]

Here is an end shot before adding the end board. This floor is built like a hollow core door. It was filled with closed cell foam to add strength and then the interior floor was added from 1/2 " plywood.

The black you see is $6.00 a gallon non fibered fence post coating. I use it on 3 builds. It takes a few days to harden up. In later builds I have gone to 2 or 3 heavy coatings of white mobile home roof coatings. ( Polar Seal or Kool seal are a couple of brands I have used )

[EZ]

There's a reason that tar was used in the 1940's. (They used what they had.) But this is 2020. I might suggest epoxy or two or three coats of thinned oil-based polyurethane.

I agree with Tony. That black gunk is what was available long ago. It is sticky and thick and overkill. Epoxy or the mix or poly is a good idea. I just use a few coates of whatever gallon of 100% latex paint I can get for $3 at Home Depot (returned for wrong color). When you think about it, old travel trailers were built with OSB as the floor (maybe they still are!) with nothing covering it and they last decades. Never understood using tar or truck bed liner - it will still be there when travel hovercraft only are allowed.

Ed