Wood floor on top of metal frame

Carlosclark · 05-09-2020, 07:52 PM

Hi I just joined Skoolie.net because I just purchased a ford E450 shuttle bus and have started converting it into my new home !

The previous owner had it cabinets and flooring in the bus but there were some leaks and mold so I decided to rip everything out and start new. When I got to what I thought was the last layer of plywood before the metal floor I was shocked to see straight through to the road upon ripping up the first section of wood.. after searching on here I have found that it is actually common for shuttle busses and trucks to be manufactured this way with the specially engineered wood straight on top of the metal frame.

I am not sure what to do here because it is a 15 year old vehicle so the floor probably needs replacing anyways. Any advice on whether to swap the wood for brand new wood? Replace with aluminum sheet metal welded on? Or just leave the existing floor (maybe reseal and add another undercoating)??

Any and all input would be super helpful!!

musigenesis · 05-09-2020, 08:17 PM

Welcome to skoolie.net. If you click on User CP in the upper left, you can edit your details and then people here will know where you are and what sort of bus you have.

musigenesis · 05-09-2020, 09:11 PM

Aluminum sheet would be pretty expensive for this, unless you have some sort of cheap source of it. There's somebody on reddit that is repairing a floor like yours with aluminum sheet, but I'm seeing prices like $200 for a 4'x8' piece of 16 ga. aluminum, which would make that a pretty pricey way to go.

I would definitely replace the old plywood with new, however. As long as it's treated properly on the underside it should be fine. I unfortunately have no idea what the proper treatment should be, although I researched this a while back when I was considering rebuilding part of my steel bus floor with wood.

Danjo · 05-09-2020, 09:53 PM

how Are the walls attached?

Carlosclark · 05-11-2020, 06:45 AM

Thanks ! This was very helpful. I think I'm gonna opt for the wood floor. Reached out to https://www.radwoodproducts.com/contact/ to get a quote. I found them in another thread for someone with similar bus. I'm wondering if it is super expensive I can do it myself by just buying hardwood plywood like Oak and paint with chemical undercoating to protect it.

Carlosclark · 05-11-2020, 06:46 AM

I am pretty sure the metal walls are welded to frame rails and any gaps are just sealed with some spray foam and other sealant product.

Carlosclark · 05-11-2020, 07:04 AM

Thanks! I think I am going to opt for wood floor. I found https://www.radwoodproducts.com/contact/ on another thread someone with a similar bus. I reached out to get a quote for my bus still waiting to hear back. I am curious if it is too expensive if I can do it my self by just buying some hardwood plywood like oak and painting with some chemical undercoating that normally goes on underside of vehicles.

I am pretty sure the walls are metal and are welded to frame rails. Any gaps appear to be filled with spray foam and other sealant products.

banman · 05-11-2020, 08:54 AM

Quote:

Originally Posted by Carlosclark

I am pretty sure the metal walls are welded to frame rails and any gaps are just sealed with some spray foam and other sealant product.

In that case I'd use a high quality 3/4" CDX plywood. Don't use pressure treated wood, the chemistry won't play well with the metal.
Paint the bottom side and edges of the plywood with an automotive undercoat or bedliner. You want an untextured bedliner if you go that route. If you're on a painful tight budget use a thin roofing tar... I would pre-cut all your pieces to ensure good fit and then take 'em all out so you can get a good coat on all the edges. Let the undercoating dry a day or two and then reinstall. Now use an wood paint on the top. Might even add a mold inhibitor to it...

Make sure you found all the leaks

musigenesis · 05-11-2020, 09:16 AM

There are a number of types of bus that have a metal frame with plywood floor like yours. These buses seem to use very strong (and presumably expensive) plywood because that's all there is to the floor (other than a thin matting on top) - passengers walk around on this so it has to be pretty rigid. The protection on the underside is provided by the quality and durability of the undercoating, not by the strength of the plywood itself (undercoating will stick just as well to crappy 1/4" plywood as it will to marine-grade 3/4" - maybe even better since the surface is usually rougher).

You are presumably going to have insulation on your floor and then plywood decking on top of that, so I think maybe you do you not need your bottom-most floor layer to be high-quality plywood. In fact, you could pre-build your subfloor as units with the crappy 1/4" plywood on the bottom, then a layer of XPS between joists of 2X wood, and 3/4" plywood on top, and then just drop these into your bus and attach them (somehow) to the open frame.

(The "somehow" I would do would be to weld threaded posts to the frame and then bolt these floor sections down onto them, which would allow you to pre-treat the underside and not have to get underneath the bus to do it. This is basically what I did with my floor rebuild, which was similar to your situation although with a different type of bus.)

Carlosclark · 05-11-2020, 10:14 AM

Do you see any concerns with moisture getting in without the pressure treated plywood or should the undercoating take care of that?

banman · 05-11-2020, 10:23 AM

Quote:

Originally Posted by Carlosclark

Do you see any concerns with moisture getting in without the pressure treated plywood or should the undercoating take care of that?

You need to find and fix all the leaks from above regardless of what your floor is...

re-read post #8...

Carlosclark · 05-11-2020, 09:31 PM

So after looking again at how the walls are attached I can see only the frame rails on sides are spot welded to frame rails on floor. The gaps are filled with these metal or wood pieces and sealed into place (see pictures).

I think I'm going to go 1/2 inch cdx plywood at the base, frame in some insulation with 2x3s and then another 1/2inch plywood on top.

Native · 05-12-2020, 02:03 AM

Quote:

Originally Posted by banman

You need to find and fix all the leaks from above regardless of what your floor is...

re-read post #8...

The OP may have meant water/moisture from below through the undercoating.

To the OP ... if you use the technique described by Banman above (an excellent proceedure) make sure you seal the plywood to the metal frame with something like Locktite PL-S40 or Dynatron 550.

Danjo · 05-12-2020, 08:58 AM

I found this page that describes plywood moisture resistance.

https://www.christinedemerchant.com/...ood_glues.html

Carlosclark · 05-12-2020, 07:58 PM

Does anyone know if the rails on the bus floor that the seats used to hook into are structurally integral to the frame of the bus? They pose an interesting challenge to build the floor around and I’d honestly rather take them out if possible.

NotAClue · 05-16-2020, 04:00 PM

Enclosed trailers do not have pressure treated flooring and the underneath barrier is tar and their floors seem to last for a long time. I believe they give the product name at TrailerShowroom . I have made interesting conversion of enclosed trailer to camper in past.

Brian S · 05-16-2020, 11:30 PM

I have an 06 E450 with Collins body. The floor consisted of really thin decintigrating galvanized sheet metal overlaid with plywood. I removed all floor down to the cross members and for new galvanized sheet metal laidddown and pink insulation board overlaid with plywood and flooring. My thinking was that plywood would retain moisture if left exposed. That of course may be an incorrect assumption. I will be driving on lots of muddy roads and in snow country.

jimburke77502 · 05-17-2020, 07:35 AM

Look into a product called Advantech. I've referenced it on this site before. They make a few different types. One where just the edges of the sheeting is treated with a resin. Then there's one that the entire sheet is treated and impregnated with a resin. When they 1st came out with this, they gave it a 50 year warranty. In my opinion, this stuff puts pressure treated and marine grade plywood to shame. They also manufacture it in multiple thicknesses, up to 1 1/8".

neverforgetyourtowel · 05-21-2020, 11:08 AM

Quote:

Originally Posted by banman

In that case I'd use a high quality 3/4" CDX plywood. Don't use pressure treated wood, the chemistry won't play well with the metal.
Paint the bottom side and edges of the plywood with an automotive undercoat or bedliner. You want an untextured bedliner if you go that route. If you're on a painful tight budget use a thin roofing tar... I would pre-cut all your pieces to ensure good fit and then take 'em all out so you can get a good coat on all the edges. Let the undercoating dry a day or two and then reinstall. Now use an wood paint on the top. Might even add a mold inhibitor to it...

Make sure you found all the leaks

I've got the same type bus as OP and am planning on doing what you've suggested here as most of the thin sheet metal is rusted out under my plywood subfloor. I'm having a hard time finding CDX that isn't pressure treated though. If I'm gonna seal the plywood with bedliner, can I use something that's listed as roof sheathing?

cweiss · 06-29-2020, 08:12 PM

I'm also watching this - I've got the same style bus and am trying to decide whether to replace the existing floor or just re-cover it.

I've also got the same seat rails along the walls and flooring. I was thinking I'd keep them because they would provide a temporary, yet solid mounting point for furniture. With t-slot bolts, it'd be easy to move things fore/aft or even take them out altogether.

You may also like: