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Old 05-25-2022, 07:07 AM   #1
Join Date: May 2022
Posts: 40
Time to put new subfloor in

Hey guys! Me again.

I finally got things dried out and most of the rotted OSB subfloor out (one tiny area left next to the slide).

My question is, should I simply glue new plywood down with a very strong adhesive or should I also screw the floor in? I only see a couple of spots where the previous OSB subfloor (now removed) was screwed and that’s along a metal rail. As shown in the photos I have to replace an L shaped piece of flooring from the kitchen directly in front of the slide out going toward the bathroom and the entire bathroom subfloor (minus what’s under the sink/vanity).

A few things I discovered:
There’s a thin piece of sheet metal (rusty where water sat on it for so long) going from the vent in the bathroom all the way out toward the kitchen (see photos) - not quite sure what this is for but it’s sort of “pushed in” and I feel it’s going to cause my new plywood subfloor to be off level when I do put a new piece in.

There’s a metal cross beams (support I presume?)

There’s an area in the kitchen where I cut to that there’s no foam under the OSB and it’s a straight drop down to the slide out motor and mechanical parts of the slide out (I took a flash light and looked down there). Luckily I don’t have to cut that far just thought it was odd. I attached a photo with my finger pointing to it.

I do have some fairly strong adhesive and I’m not looking for a “professional” job I just want to be able to use this damn motorhome that I bought and have had many issues with. So any advice is highly appreciated.

When I was pulling the wet/old OSB subfloor off it was glued the entire way.

Another couple of questions I had were can I somehow use epoxy (west system) to reinforce the new floor when I get it down?

Is it ok if I get the new plywood subfloor down using multiple pieces of plywood? I highly doubt I’ll be able to get it down with one piece. I would imagine 2 or 3 minimum. Will this cause issues?
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Old 05-25-2022, 07:44 AM   #2
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I had a ~6'X4' section I had to replace.

On my coach the manufacturer only used a vapor barrier to protect the underside of the OSB plywood to protect against the road elements, I had tow layers of ~5/8" OSB. I was able to salvage this and made an attempt to adhere it the underside of the new plywood I put down by spreading liquid nail and then using a foam roller from underneath once the new plywood was dropped into place. Hope it works.

I decided to use a 3/4" piece of treated plywood for my first layer. I used exterior primer paint on all sides, painted the bottom and sides first, then laid it down and pained the top. I did put some additional plates underneath at the seams to tie the pieces together. The 3/4" is stronger then 5/8" for the spans between the metal "joists" underneath.

I then had to make up the difference with a a different sheet and had a piece of exterior siding that was "close enough" to use and this has a 50 year warranty so it is very durable. It is a very dense product also.

I then put down Pergo LVP flooring.
Jim J
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi
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Old 05-25-2022, 08:56 AM   #3
Join Date: May 2022
Posts: 40
Thanks. I just read your thread.

Unfortunately I just came across another problem. Underneath that sheet metal in the hallway is an empty space. Not sure how far it goes down but that’s besides the point.

It appears I’m going to have a hell of a time trying to glue the plywood down in this area. The sheet metal is pressed down and wobbly so even if I can get an L-shaped cut and fit it in with glue, the pieces with glue aren’t going to touch the sheet metal.

I’ll take a video and post it

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Old 05-25-2022, 07:19 PM   #4
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From what I am seeing, I think the sheet metal is ductwork for the furnace. Using cleats along the edge where the sheets abut each other with lots of adhesive should do it. The heating ducts don't normally support the floor, they just lay there beneath and the cross members are the support. If not enough room for wood cleats, a strip of metal which has been tapped for flat head screws and extending an inch or so under each piece would do. West System epoxy thickened with silica is very strong and would be great between the sheet edges. Good luck.
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Old 05-25-2022, 07:35 PM   #5
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The structure of my coach is all metal and there are floor joists that go from side to side. The original subfloor was screwed to the joists, I do not believe anything was glued down.

When I installed new flooring I screwed it to the metal joists using self taping screws. Ain't going anywhere!
Jim J
2002 Monaco Windsor 38 PKD Cummins ISC 350 8.3L
2005 Jeep Grand Cherokee w/5.7 Hemi
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Old 05-26-2022, 07:41 AM   #6
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Thanks for the advice and knowledge everyone, I highly appreciate it!
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