Replacing entire subfloor one piece at a time.

[Cruiseomatic]

'06 Cavalier. Starting total remodel/rebuild. Starting from the bottom up and thinking about the sub-floor. It has some patches but in 2 places. Factory floor is particle board and the dealer replaced the rot with OSB that has swollen in couple places. I was thinking of replacing it all with 4X8 sheets of 5/8" or 3/4" marine grade plywood one sheet at a time so not to disturb the wall framing. Once cut, knocking the old sub-floor out shouldn't be that hard. Should only take 7 or 8 sheets. I also am replacing the undercarriage sheeting with "plastic cardboard" and thinking of sistering 2X4s on both sides of the factory floor studs with either 1/2" bolts with washers through them at set intervals or screwing them together to mount the plastic board and add strength. This is about a month or two in the future but it has been bugging me and I can't find much online about it. Not too worried about cost as I am doing it right the first time to last a long time. Once this trailer is done, It will basically be a park model. I do know that pulling the sub-floor will be a pain but it will be worth it. Thanks.

[westend]

keymastr wrote:
I disagree heartily. I would ONLY use marine grade plywood and I would also waterproof it before installation making sure to coat all edges so water will not be a problem in the future. I would treat any wood I replaced this way. Your labor is the big investment, why take a chance? A trailer WILL get wet at least once.

Your post belies that you've never used marine grade sheathing. There is no need to treat edges.

The last time I priced marine plywood, it was 8 times the cost of CDX. Probaly 3 times the weight, also. A half gallon of paint across both sides is a lot cheaper and, for this use, is still overkill.
The original, unsealed 5/8" CDX decking in my trailer was still good after 45 years. It was only damaged where long time leaks had let an outer edge become immersed constantly and underneath the water heater that must have leaked at some point.

I'd advise the OP to open the walls before starting on the decking. He'll need to remove fasteners and pry it up (at a minimum) to remove and replace the subfloor. It will be much easier with wall paneling removed.

I'd also advise the OP to get paper in hand and outline the schedule of construction processes before removing a nail. I've done this restoration thing and it would behoove anyone trying to at least get a preliminary plan in order. That is, unless you enjoy tearing out your new work to accommodate another forgotten piece.

Check out the thread in my signature line, "The Cowboy/Hilton" for some ideas.

[keymastr]

I disagree heartily. I would ONLY use marine grade plywood and I would also waterproof it before installation making sure to coat all edges so water will not be a problem in the future. I would treat any wood I replaced this way. Your labor is the big investment, why take a chance? A trailer WILL get wet at least once.

[kcfissel]

If you are planning to reinforce the floor joists, you might consider strips of the marine grade plywood on each side attached with screws and a good construction adhesive. I would think you would save some weight as opposed to (2)2x4s.

[Dr_Quick]

For a sub floor "Marine Grade Plywood" is not Necessary. Marine grade means that plywood has a high quality surface for a natural finish, and it is VERY expensive.
Standard CDX waterproof plywood sheathing/subfloor will work fine. I have used CDX in two trailers to rebuild floors and it has worked fine.

[Cruiseomatic]

The leak was taken care of long time ago and the trailer is now in a 12X45 garage. Yes, the floor extends under the wall. This is a build to last for a life time. After measuring it tonight, the running studs are 1.5" thick and 2.5" wide. 2X3 maybe? I was thinking of replacing it one sheet at a time. All the fasteners are getting replaced. Once the floor studs and sub-floor is finished, I had planned to use a closed cell spray insulation underneath then on top use a bondo type filler for joints and imperfections. My fear is mostly structure integrity. Once the floor is complete, the walls are next with their staples...

[westend]

I removed and replaced some of my floor in sections. As Bob said, the subfloor is installed underneath the walls. I was able to remove the sections under the walls by cutting fasteners, prying out the old, and sliding new sections underneath the walls. A right angle grinder and reciprocating saw were my friends. I had the walls opened up so attachment through the wall sill was easy.

The original sheathing in my trailer was 5/8" plywood and most of it was OK. Where i had damaged sheets, I replaced with the same. Marine grade sheathing is overkill. It will add considerable weight and expense for small improvement. If you have concerns about future damage to the floor, painting the plywood or sealing with marine varnish should deter that.

One thing I did as an improvement was filling the floor joist cavities with extruded foam. That greatly increased the R-value and comfort level. Since I replaced the original carpet with an underlayment of rubber and laminate flooring, I only had to fill the joints and screw holes lightly with a floor leveler. If an owner chose vinyl as a finished surface, attention to achieving a smooth surface would be necessary.

Good luck with your floor!

[BobsYourUncle]

I once replaced the entire floor in my TT.
Big job to do it right.
The floor sheeting goes all the way to the outside edge front to back.
I literally disconnected everything and jacked the entire walls roof everything up off the floor and replaced rotten joists and plywood in one piece edge to edge.
I used 5/8 T&G
Big job but it can be done.

Then I put new lino down, one piece all the way through front to back.
Then put the walls back down, partitions etc.

[ScottG]

Sounds good but dont you need to fix what ever is allowing moisture in and damaging the floor?

[azrving]

Does the floor go under the walls? Sounds like a big job but you will know it inside and out when done. We love pics.