Subfloor Installation

[Scratchy]

Hello All! Long time reader, first time poster. I’m looking for some clarification and advice on installing a subfloor. I’ve purchased a 1996 Thomas - 65 passenger bus. My game plan is based on reading the posts in this forum. I’m looking for some confirmation I’m going down the right path and any advice or suggestions if I’ve missed something….

1. Remove seats, old flooring to bare metal skin of bus.
2. Clean, sand and repair any existing rust spots
3. Silicone seat bolt holes along with any other gaps, cracks, holes in the floor.
4. Paint the metal floor with Rust-Oleum.
5. 1’’ Owens Corning Foam Insulation – taping the seems tight.
6. Lay a “Vapor Barrier” down – 6 mil polyethylene plastic sheeting
7. ¾’’ plywood subfloor and painted again with Rust-Oleum.
8. Once all my wall studs have been seated - Laminate Flooring.

Vapor Barrier
I’ve read a lot of contradicting posts in regards to the Vapor Barrier – one says between the metal and insulation, other says between the insulation and the plywood subfloor. Which is it or both? One states plastic on top of metal traps moisture and another says if the plastic isn’t against the metal, the insulation is exposed to moisture. Not sure which to believe…

Fasteners
Typically, how thick is the bus metal flooring? Reading other posts, I understand some have fastened their plywood subfloor with wood-to-metal screws. Any recommendations on the type of fasteners to use? How far are they screwing the fasteners into the metal floor? If the fasteners go through the floor, wouldn’t be just as practical to bolt the floor down? By screwing down the subfloor through the insulation and vapor block am I not exposing myself to potential moisture problems? Is there another ways to fasten the subfloor to the bus?

Plywood Subfloor Thickness
I’m planning on using ¾’’ plywood for the subfloor as I mentioned above. When it comes to roughing in stud walls or securing bunk beds to the floor is there any recommendations or best practices? I intend to fasten to the roof for additional support on the opposite end of the stud for additional support, but I am having a hard time grasping the ¾’’ plywood is strong enough to hold on its own through toe-nailing screws or am I being overly concerned?

What else am I missing or need to be aware of? Thanks in advance for your assistance. Also, thank you to all who have posted pictures and how-to tips, they’ve been very helpful.

Scratchy

[the_experience03]

I used furring strips to affix my plywood. The furring strips were affixed with good self drilling screws countersunk into the wood. Look for TEK screws as these suckers drill and hold. However, the screws aren't my primary form of attachment. I actually used liquid nails for much of my construction. The screws just held it in place while it cured. Everything that I used liquid nails on has held up beautifully. Other things that I just used screws on have not due to body flex shearing the screws. I think a lot of this has to do with the terrain I have taken my bus across, but I am a big fan of construction adhesives now.

[newbusser]

I plan to seal holes in floor with fiberglass, then a coat of rust-o-leum, then a thick coat of bedliner without the grit.

Plywood will go on top of this and them finish flooring.

Not using much insulation in floor because this will be parked during the colder months and used primarily during summer.

[TygerCub]

Originally Posted by newbusser

Not using much insulation in floor because this will be parked during the colder months and used primarily during summer.

Don't forget guys, insulation isn't for any particular season. Insulation merely helps maintain the interior at a more comfortable temperature than the outside, no matter if it is hot or cold. It can keep the heat/cold inside, or out.

It also serves another function... sound barrier. Road noise, neighbor noise, your noise (don't come knockin' if the bus is rockin') ... whatever the situation, even a little insulation will help.

It's just an opinion, of course, but insulation is one area I wouldn't skip. Even if you don't see a need for it now, it's not something that's easy to add later.

[Scratchy]

Howdy folks.

Thanks for all the suggestions and reassurances. Just a quick update on the progress, the seats are out and the floor was stripped down to the bare metal. What a project - I couldn't believe how well the old plywood floor was secured to the actual metal floor - yikes. I have a couple hours of silicone ahead of me to do in filling all the nail holes. Surprisingly enough the floor was in really good shape. My main rust spot areas were the wheel wells and the back door. I've wire brushed the surface rust areas and used a product called "Ospho" as recommended from another post/thread here on Skoolie. It’s a rusty metal treatment product used in preparation for painting old rusty surfaces for better adherence of the paint. I only used it over the wheel wells and the back door - again b/c the rest of the floor was in good shape. I must admit the stuff stinks to high heaven - make sure to have good ventilation, but works wonders and cheap. I'd recommend it for no more than what it costs. My first coast of Rusty Metal Rustoleum Primer has been put down. I’m going to put a second coat of primer – just b/c I have excess. Next I’ll paint and start prep for subfloor installation.

Just thought I would share my thoughts on the Ospho product and give an update on progress.

Scratchy

[turtle]

Originally Posted by mightybus

My formula is; steel floor. red rosin paper,then plywood, last; wood, vinyl, marble, carpet etc. finish floor.
The rosin wicks away moisture and condensation from the steel (the actual moisture barrier), and contains it until the moisture can migrate up and out.
You can completely forgo the plywood and or keep it and add foam under it if you choose.
This way your bus won't ever feel damp or stinky and moldy.
The foam is not really needed in my opinion.

I've painted (with Kilz oil based paint) and sealed (with silicone) what wood was already attatched to the steel floor. I feel it's too late to use it under the pre-existing wood at this point. I have the red rosin paper thinking it went on top of the wood. Would red rosin paper still work to help in this case?

Turtle

[Seeria]

While we are on this flooring topic...

Is it possible to use radiant barrier type goodies http://www.radiant-technology.com
THEN put plywood down rather than putting in foam boards? Would it still be the same effect Rvalue wise?

[turtle]

Originally Posted by mightybus

Hi Turtle. I assume you did not tear up the original plywood. And painted over it. Well of course it doesn't matter much now, but believe it or not you shouldn't have painted the plywood unless it was your finished floor in my opinion because the paint will trap moisture in the plywood to a certain degree. I would use red rosin paper on top of the plywood because it will wick any moisture away from the top of the painted plywood and any material you may place on top of it. I would make micro pricks or small drill holes through the painted plywood so moisture can escape in my opinion. Red rosin paper is by far the greatest thing you can put in or on your floor in my opinion.

Ya, I'm thinking I over-sealed. Perhaps the holes, then the red rosin is the best solution at this point.

Turtle

[turtle]

Now that I've faced reality and tore up the plywood to start from the steal base, I'm wondering about sealing the holes in the floor. Would it be helpful to actually leave holes in the steal for better ventilation for your red rosin paper(or vapor barrier) and plywood? Why seal the holes at all?

turtle

[Sojakai]

While those holes will let stuff out, they will also let stuff in. Better to paint the floor and then seal the holes with fiberglass or caulk or something.

[ramairws601]

I agree, I intend to prime my floor first so the primer gets in all of the holes good, then seal the holes up. anywhere you let water in is only gonna cause trouble. When I stripped my wood flooring out I realized they put the floor down and then put the trans cover ontop the wood. that left the entire edge of the wood around the trans exposed to water being splashed up and also allowed it to get under the floor. when I do it I am sealing my cover down metal to metal and cutting my wood around the cover.

[EricW]

I figured I'd just use this thread instead of start a new one..
So I have used roof sealant on all the roof seams and am recaulking all the win does which should bring me to the point of being able to put my subfloor down. The holes in floor are patched with silicone and aluminum tape then primed and painted with rustoleum. Also used ospho to clean up the rust before painting. The materials I got for the subfloor are 1in 25 psi foam board insulation and 3/4 plywood. I also got 1/2 in plywood that I cut into 2in wide strips. I was planning to stack 2 strips and run them around the perimeter using the self tapping TEK screws and PL premium. I was also going to put one runner down the middle and possibly one where each plywood seam will go. I was planning to screw the plywood into the strips but not through the metal. It seems it would also be wise to space the plywood sheets by 1/8 in and away from the walls by 1/4 in. How far apart can/should my screws be on either application? I got some 30 roofing felt... should that go under the plywood or under the insulation? If it goes under the insulation should I put plastic over the insulation so it doesn't squeeking against the plywood? What is best to put between my gaps of plywood to fill the cracks? Also should I space my runners that go around the perimeter away from the wall? Should I even use the runners around the perimeter? Any advice or opinions welcome as I am tackling the floor tomorrow. And I already bought the plywood Nat so probably gonna do this in some fasion. Hehe. Not a lot of the build threads seem to go into much detail and I'm a little ocd and feel the need to ask before tackling it but thanks to this website I was able to get this far with a plan

[Josiahdr]

Hey EricW,

I Just did the same thing roughly. I used great stuff to fill in the cracks and it seemed to work great. On one board i did not cut it small enough and it seemed to bow. That would be my biggest tip if using great stuff, just leave room for it to expand. I put screws in every 6" or so and a couple extra on the corners. Here is how I did it, hope it helps.

https://www.youtube.com/watch?v=ABrj...SqeoRRfRuYHtAl

[California Dreamer]

I want to forewarn anyone that's going to put in insulation on your subfloor that as you can see in the video this enthusiasts built up the floor so much that his head is now hitting the ceiling. This is not a factor in most buses since there's plenty of height room. Be very careful on what subfloor you choose and what insulation and how you're going to install it because you're going to be making your floor thicker and thicker thus removing headroom . Ouch I already hit my head just watching the video

Originally Posted by Josiahdr

Hey EricW,

I Just did the same thing roughly. I used great stuff to fill in the cracks and it seemed to work great. On one board i did not cut it small enough and it seemed to bow. That would be my biggest tip if using great stuff, just leave room for it to expand. I put screws in every 6" or so and a couple extra on the corners. Here is how I did it, hope it helps.

[California Dreamer]

And he doesn't even have the interior roof set up yet . Ouch I just hit my head again

[slaughridge85]

Originally Posted by California Dreamer

And he doesn't even have the interior roof set up yet . Ouch I just hit my head again

He may be planning on doing a roof raise...

[EricW]

I unfortunately am not doing a roof raise due to my lack of knowledge and time but don't plan on doing a crazy amount of standing. Cooking may be a pain but perhaps I'll devise a comfortable way to sit or kneel like a memory foam topped stool type deal. I figure most of my time will be spent sitting, laying down or adventuring outside the bus. I think the extra insulation will be of more value than an extra inch of headroom.

[PoolRoom]

I JUST got my bus down to the metal floor. I have NO extra headroom... what is the best minimal thing to do to the floors!!??

[Robin97396]

Linoleum?

If I had no room to insulate I'd put down carpet during the winter. Disposable carpet. It actually insulates quite well by itself and reduces condensation during cold weather. Synthetic materials would the best.

[EastCoastCB]

Originally Posted by PoolRoom

I JUST got my bus down to the metal floor. I have NO extra headroom... what is the best minimal thing to do to the floors!!??

Wear slippers.

Or-