Bathroom Floor Replacement

The following directions were written for a mobile home bathroom floor replacement project. Bathroom floors are the most common floor problem in mobile homes. However, the same process works just as well for floors in any room of the mobile home; it’s just lots easier because you have more room to work and don’t have to deal with the plumbing cutouts.

Buy enough A-C 3/4″ exterior grade plywood to completely cover the bathroom floor. You will also need screws long enough to go through the plywood and the existing flooring and the new vinyl or carpet you will be putting down (I really prefer vinyl). Since mobile home bathrooms are often small, you can usually find inexpensive remnants that will be as large as you need. You will need a new wax ring and possibly new flange bolts to re-install the toilet.

Vinyl, especially cheap vinyl, will quickly conform to any holes or bumps in the material it is laid on. If you don’t cover every screw head you will soon be able to see each one and tell whether it was a Phillips or straight drive. To make sure the new floor is absolutely smooth you are going to want to countersink the screws and make sure any seams in the floor wood are filled.

I know two ways to do this. Floor Leveler is a concrete based product sold at home improvement centers. It is mixed with water and the mortar is troweled into the holes and voids to smooth them. It has to dry at least overnight but is cheap.

I prefer to use Bondo which is plastic filler used by automotive body shops. You mix as much as you need with a catalyst and it will be hard enough to sand in 30-45 minutes. You need good ventilation and if you are only doing one job will have a lot left over.


Shut off the water to the toilet. Many homes lack a stop on the toilet supply line. This leaves you a choice: (1) turn the water to the home off and hope you finish before someone needs functional plumbing, or (2) figure out a way to cap off the line. I prefer to cap the line. It will come in handy later, and it gives you more options if you run into surprises while working. Next remove the toilet and get it out of your way. Remove old carpet if present and hammer down or pull nails etc.

Cut the plywood to fit the floor as exactly as you possibly can. You are not likely to be able to cut one piece and get it into the room. There just isn’t enough room to slide it around as much as you will need to. Make sure that the cuts you are forced to make place any seams as far away from the toilet as possible. The toilet is the place most likely to leak and it also gets the most use.

With plywood in place and the holes cut for the toilet and water supply line, use two pieces of scrap wood to make a collar for the toilet drain line. Get them against the drain line below the flange and drive screws to hold them in place. This will make sure that when you go to mount the toilet you don’t have to try and figure out how to hold the drain line up while you set the toilet on it.

Fasten the plywood in place with lots of screws. I liked to make sure I hit the floor joists if at all possible and had a screw about every 16″. Fill the seams, edges and screw holes with Bondo or floor leveler, let set and then sand flat.

Hopefully you have had the new vinyl unrolled in a warm place and it is now willing to lie flat. Cut it to fit the bathroom, spread the adhesive and smooth the vinyl into place. You may want to use a roller to get all the bubbles out from under it or may find that for such a small space any bubbles can be worked out by hand or with the help of some scrap lumber. If you salvaged the baseboard trim strips and did a really good job of fitting the plywood you may find they are enough to cover the edge of the new vinyl. More likely you will either decide it looks OK as-is or will want to put down some quarter round to cover the gap at the walls. It will also help make sure the vinyl doesn’t curl up at the edges.

Remount the toilet, reconnect the water supply line, and check for leaks.

You will probably need to put down some sort of trim strip at the door(s) to make sure no one catches their foot on the edge. These come in a multitude of shapes and you should be able to find one that does what you need without making an unacceptable ridge.

{ 37 comments… read them below }
very informative…..but why lay the new flooring on top of the old one?
It saves a lot of work. If I take up the old I have to cut the old flooring free and clean nails, etc., I have to make sure the new flooring is carefully measured and cut so it is properly supported on all sides. That’s not a big deal if you have carpentry skills and the right tools. For many, it is a serious issue.

Teresa in Texas
I had to completely remove all the partial board – 8 ” from the tub forward; it was like a flaky sponge falling apart and I did this by my self. I drew lines on the floor to carefully start cutting out the partial board by using a reciprocating saw-a little at a time. Then beat the heck out of the floor with a hammer being careful about locations of boards, electrical and existing plumbing since I had no idea where these were located. A helpful tool was my digital camera-I could stick it under where I was working, and check and make sure what was there while I was working . Finally got all the bad board out, then I sistered up the 2 x 6 joists and re-enforced between them with 2 x 6′s as well- making sure that everything stayed level.
then I had to cut the 3/4 inch plywood into sections-reason being because of existing plumbing. I measured and re-measured and finally got everything cut to go around the plumbing, screwed down everything. There were gaps between the pipes and plywood, and between where I butted up the plywood best I could. I used the spray “Great Stuff” being very careful with it to fill in the gaps. Making darn sure I had on latex gloves and plenty of paper towels and only filling in the gaps half way because this stuff swells up and cut the excess off with a serrated knife. So far so good now, I am letting it dry over night before proceeding with the bondo.
I am glad I found this web page about the bondo-excellent idea! I didn’t want to use the leveler compound for my 5 x 5 bathroom. At least with the bondo you can fill in the cracks, and counter sunk holes from the screws, and keep leveling it up until you get it just right.
Teresa 12/30/2010
I get asked why I suggest just covering the old floor with the new. Can you imagine the price I would have to quote to bid a job done this way?
Glad the Bondo suggestion helped. Nice use of the digital camera. You should end up with a really nice floor. If you have any before and after pictures you would like to share email them to me.

I own a 1978 8×40 park model (living area is 8×37), and just purchased a 1970 mobile home with a 12×40 living area. I’ve approached floor repair in the way Paul suggests and in the way Teresa used. Even though Paul’s “overlay” method may use more material and address areas of the floor which may not need repair, it’s safer, easier and a much better investment of one’s time.
I would use the method Teresa describes again only on a small area that was not affected by rot or water damage–for instance, if someone dropped a weight and dented the floor–and where I could peel back the floor covering or replace “press and stick” tiles. If you’re looking at a kitchen or bathroom floor that’s rotted-out, it’s worth it to shut off the water, lift the toilet & possibly the lower cabinets, and lay down plywood.
To address the uneven edge, get creative. Depending on your needs & preferences, if the overlay needs to transition from one living space to another you could use an angle grinder or a router on it. There are all manner of products on the market for transitioning between one type of floor covering to another–look at them for ideas & see what works for you.

With our floor in our mobile home, the flooring between the bathtub/shower and the toilet is slowly “dropping”! It is already bad enough that the toilet is sitting at a slight angle and the tub/shower is not in the best condition so we were planning on changing out the tub/shower with a jet tub when we decide to redo the floor (Needs to be really soon). If we are having to take out everything in the bathroom anyway and the floor is warped to the condition of what I mentioned, is it still better to apply the new floor on the old one or should we take out the old floor? We bought the place like this but need to fix the floor! I’m afraid of the old floor having mold! If I put the new floor right on the old floor, then how would I level the new floor in the areas that are already sinking? Thank you greatly if U can help!
Have you found and fixed all water leaks? That is the first priority.
My logic for putting new flooring down on top of the old is that it requires much less skill. If you take out the old flooring you have to measure and fit the new material so it is properly supported. The floor joists will be 1 3/4″ wide so your measurements and cutting have to be accurate enough to use all of the 7/8″ that is available. Notice we are talking in eighths already. That isn’t so easy to do.
If you put down 3/4″ plywood it won’t matter if the floor has sunk under it because the plywood can handle the weight. If the existing floor is destroyed over the joists you will want to shim (place wood strips) on the joists to bring the support level up to where the other parts of the floor are.
I hope this helps.

Jean Brrrrrrr MN
I have a 1996 Dutch home we bought the home with carpet in the bathroom. Our toilet starting leaning we tore out the carpet and much to our suprise all the sweating the tank does in the summer (no a/c warm temps don’t hang around) ruined the floor. Also to our suprise we only have one floor, no sub floor. So I elect to keep orginal floor and add sub floor because it will help insulate my floor better. Anything I can do to keep warmer in 34 below zero temps I’ll do.

Can I lay 3/4 inch plywood right over existing linoleum and floor in the kitchen? Can I butt the new plywood up to the cabinet and door area then screw or nail the new plywood into the existing plywood (right over existing linoleum and old floor), and put some kind of trim over the uneven areas against the cabinets and door? Tearing up the old just does not appear to be an easy “do it yourself” option. This is 1971 doublewide. Please help
That always worked for me. I would use screws, not nails, to anchor the new floor. I would try to hit floor joists with the screws, not count on the old subfloor to hold well.

I am in the same predicament as a couple of the last people. I pulled up the carpet in my parents bathroom which had vinyl under it. The particle board is a mess and is swelled. I will need to pull the wood up and install 3/4″ plywood. I am handy and have a CS License. I never fooled around with a mobile home before. It sounds like from some of the comments above that I will be able to screw into 2×6″ floor joists. Is that what I will see when I rip the particle board.
Yes. They should be a lot heavier than 2 x 6

I had carpeting in my master bath 2000 Fleetwood, doublewide. I pulled up the carpeting and found that part is vinyl. It appears the vinyl is under the shower unit and toilet is partly around the rest of the flooring (halfway through the bath with big staples on the outside edge). The entire floor appears to be at least B plywood with many nails and dents. I am not sure what kind of flooring to replace the carpeting with now??? I was going to go with the cheapest (not carpet), but underlayment does not appear to be the best. Please advise, thanks.
One of the reasons carpet is so popular with mobile home manufacturers is the sins it will cover. You can’t put vinyl directly onto the old floor because all the dings and dents will quickly show. At the same time, I can understand not wanting carpet in a bathroom.
I had some luck preparing floors for vinyl using an automotive dent repair product called Bondo. It can be sanded after it hardens to make a really smooth surface.

All good advice.. I’m getting ready to do my own repairs to an older mobile home I am buying. The floor in the main bathroom is mushy and will be replaced or a new one laid over it, depending on what I find under the carpet. I like the idea of just laying a new floor over the existing floor because it sounds a lot simpler but no one here has addressed the issue of the bathtub.
If the floor is mush under the tub as well is that tub going to have to be lifted out to repair it? But if the floor is ok, do I just butt the new floor up against it? And then add the usual caulking/sealing at that point once the vinyl has been laid down?
I guess the question you will have to answer is if you think the old floor is strong enough to support the tub properly. If you get someone heavy standing in one end, will it hold their weight? If not, certainly you need to fix under the tub too.

I have two bathroom floors that need replacing due to sewer back-up in the park. Under the toilets water came out on the floor and ruin the partial board and warping the whole floor. The floor is now dry, what is the best for me to do, tear apart the floor and replace it or overlay with 3/4″? Also what do I do with the toilet drain, is there a way to get a tight fit without leaks? I think my biggest problem is the drain, I’m not sure how to approach this, and suggestions?
My personal preference was to overly the old with new plywood. It seemed like that would be less work than cutting out the old, possibly tearing up a saw blade(s) on nails, and then pulling nails and scraping old glue off the joists to make a smooth surface. If you have the right saw and experience cutting to a specific depth it may be easier to remove the old.
As far as the toilet drain you just make sure the flange is fastened tightly to the new plywood and a new wax ring takes care of any leak concerns.

I’m planning to rip out the master bath in my 1977 Barrington MH and replace everything. In reading these posts, particularly Dee’s, it appears I can lay 3/4 AC over the existing floor. There are no wet particle board issues in this case. The question is, will the floor and 2 x 6 joists support a cast iron antique claw foot tub? If not, is it possible to reinforce the floor in some way to make this tub possible? Or should I bag the idea?
Thank you.
I am not an engineer, but I wouldn’t think the tub would be any heavier than a piano or filled bookcase. With 3/4″ plywood the weight should be distributed well.

ok so i have a question if you put the new floor down over top of the old if there is any water damage doesnt that create a place for mold to grow and wont it make the new floor rot even quicker?

I am assuming that any water leaks have been fixed and that the area has been completely dried before you put down the new floor. In most cases people are covering failed particle board. That stuff comes apart from just getting wet, it will fail before it has time to rot.

How do you determine if a mobile home bathroom floor needs removing prior to replacing with a new one ? The floor appears to be rotten. If I put plywood over the existing floor, might it fall in ? As a few other people mentioned, the toilet is sagging. Thanks,
I guess in some ways it’s a judgement call. I would remove old flooring that would break away easily with a hammer and/or which was obviously swollen up or soft. I would smooth the exposed joists and put a strip on top of them to bring the level up. I would install supports between the joists to support the edges of the replacement plywood.
I am assuming that everyone doing this kind of repair is using 3/4″ exterior grade plywood. That is much stronger, water resistant, and inflexible than the original particle board.
With the floors I worked on I thought covering the old saved time and money. Of course I live in a dry climate so the the old floor had usually dried completely before I worked on it.
Thank you very much for your help.

Complete newbie looking for guidance! We were given a free mobile home (1984 Redman double wide.) The guy died many years ago, but his cats stayed in it for some time. Ew. We’ve ripped up the carpet and padding, and the floor is made of particle board. Thanks to a leaky roof (fixed) and leak in the kitchen (fixed) the floor swelled up like crazy and “refreshed” the cat pee smell. It’s AWFUL! We would like to save as much of the floor as possible due to money constraints, but we’re also concerned that the smell might be an issue even on the particle board that isn’t swollen.
My question is do we replace the entire floor or do we just cut out the swollen, bad parts, replace with plywood, then Killz the whole thing to seal in any possible smells?
There is a lot of swollen particle board throughout the house, I’m wondering if replacing the whole floor with plywood would be easier than all that cutting and replacing each swollen piece, considering the extent of the damage, or is it possible to bleach it, Killz it, then cover the whole thing with plywood? (Even the swollen stuff?) There are some holes in the floor that obviously need to be patched as well. HELP?
Wonderful word “free”. You should always look a gift horse in the mouth
It sounds to me like you would be ahead to cover the entire floor. You are right that there may be smell from what looks like undamaged flooring. The urine can also get into/onto the walls. I think thorough (as much as is possible) cleaning, bleach, Kilz followed by new plywood would be the way to go. That will leave you with a floor that feels wonderfully solid, with no worries about weak spots.

I just purchased a 1974 DW, of course a gut job…I was wondering if I should go over current sub-floor before I re-level? or should I spend the expence to even re-level the MH..Thank you
In my mind leveling and floor repair are two different issues. If the home isn’t level that needs to be done at some point. I don’t see any reason it has to be done before you work on the floors.

I just began floor repairs on my 1981 14×70 mobile home and wish to share my experiences in case they help anyone.
I had a waterheater go nuts while out of town and the result was major water damage. I got the usual sagging and falling through floor, but also got huge waves that were high spots because the swelling floor had nowhere else to go than up.
His idea of just laying 3/4 plywood over the top of your existing subfloor is ideal! Circular saws have guides on them that prevent you from cutting the old floor flush at all walls, cabinets, etc. So if you cut the old out and piece in the new, your seams will be 2″-4″ into the room at every wall. With vinyle sheet floors, this seam WILL show through in time. So now you are forced to spend more by laying 1/4″ luan over the plywood you put in.

Here’s what I did: I cut all the high spots out of the old particleboard floor. In the sections I had cut out, I used 1×4′s to shim the joists up level to the remaining particleboard (since a 1×4 is really only 3/4″ thick. I then laid tar paper over the entire subfloor (overlaping the seams and taping them with duct tape…also allowing the tar paper to run up the wall several inches). I then laid 3/4 plywood over the tar paper and screwed it down into all joist locations. (remember to measure and mark where your heating vents are, and then with a hole bit, drill a hole through the new floor at the marked vent locations and then use your jigsaw to cut the vent hole to size). From there, just lay your flooring of choice, trim the tarpaper down low enough so your baseboards will cover it, and then put the baseboard trim on. (I recommend running that tarpaper layer up behind the baseboards, because often old mobil homes develope leaks in the aluminum siding and this will prevent water from leeching into your new subfloor).

I forgot to mention that this process can lead to one problem: will your front door have clearance to open over the extra 3/4″ of floor?
Here is my thoughts on that: lets all face it, your average factory trailer entry doors are flimsy aluminum cased styrofoam. I can attest from a time I lost my keys, one swift kick in the center folds this door up enough to bypass your lock and open it lol.
What I did: I bought a used, prehung HOUSE steel door with jamb. It will be taller than your typical trailer entry door, so carefully remove paneling, remove flimsy door frame and the header, and build a new door opening of 2x4s to the proper dimentions of a real house door. (There is plenty of room for the taller house door and a proper header). I used a 2×4 on the bottom of this door opening like when framing a wall, so this brought the new door up high enough to clear my added layer of subfloor and even left room for hardwood floor on top of that!

Hello. I have replaced floors in a trailer, bathroom and other rooms, using both methods mentioned here. I do agree that the putting the new on top of the old is much, much easier. However, I also use a layer of plastic, the 3 or 4 mm thickness, between the old and the new boards as a water/moisture barrier. That is particularly useful if the belly of your trailer is not 100% and you live in a climate with lots of rain or snow. The plastic will stop any moisture from getting up to the new boards and causing them to rot.
I put the plastic in with a staple gun. Just a small staple gun will work and then use an exacto knife to cut out any holes that need to be cut out.

The new boards are then placed over the plastic as mentioned here.
Also, when you use the new boards you may have to get an extension for your toilet hook-up. The extension goes on the end of the drain pipe that comes up to the flange. Usually it will be a part that will include a new flange. The flange is the part that the toilet bolts goes into.
The best way to make sure that it fits your drain pipe is to remove the old piece, clean it up a little bit, and take it with you to the store. The plumbing section person should be able to match it up with a new piece.

The problem with this is that sometime the new piece will actually be a little too tall and your toilet will rock. That can be fixed simply by getting some 1/4″ board and making a cut out that will fit under the edges of your toilet. Don’t forget to cut out the area for the drain. The 1/4″ board can be painted to help stop any moisture from condensation affecting it. The paint will also make it less conspicuous.
I also tend to use OSB instead of plywood for the floors. The blue edge OSB is preferable and it will often have an interlock cut into the edges of it. 3/4″ thick blue edge OSB is heavy and should be handled with care.

I’m getting ready to lay the plywood down. My problem is how I’m going to figure out where to make the holes in the plywood for the plumbing directly under the toilet. I’m stuck and any assistance would be appreciated.
I remember the time I had to cut the faucet and shower pipe holes in a replacement shower surround.
What if you drive nails into the four walls so that sting stretched between the nails mak and X over the center of the drain hole. Take the string off, put down the plywood, re-tie the strings and X should mark the spot.

Dear Paul, thank you, thank you, thank you! Most mobile home owners are on a tight budget and have to do the repairs themselves. Because so many of these homes are older, it’s hard to find information on how to do this properly. I still haven’t finished my bathroom due to relying on my family for help, but it will get there. The main thing is there are no new leaks.

Paul, I may have missed this question, im wondering how to make the floor in bath match up to the floor in living room? it will be 3/4″ higher than original flooring..i havent started yet, but had bad water break at toilet and toilet falling in. thanks for you wonderful help, im retired and like a lot of m/h owners on a small budget..thanks again
Hi Barbara,
You are correct, it will be higher.
That said, when I thought about the effort needed to remove the old flooring and install new versus putting plywood over the old, the 3/4″ level change seemed like a small issue.

It also seemed like there were a variety of modifications that would reduce the tripping hazard. For example, you could bevel the edge of the plywood so there was no sharp transition. If there is carpet in the hallway outside the bath door you could add a little padding (or replace the old, beaten down pad) to make the levels match. There is a wide variety of thresholds available at places like Home Depot that would make the transition more gradual.

As always, the correct answer is “It depends” on your individual circumstances but those are my thoughts.
Thanks for posting,

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