How do I know the subfloor is rotting/rotted?
March 17, 2010 10:44 AM   Subscribe

How do I know the subfloor is rotting/rotted? Plumber came by and mentioned this about the bathroom; how bad is it?

Plumber came by last night to fix a little problem with the fill tank of the toilet…While he was here, he mentioned that the subfloor had rotting wood; that the toilet rocked and it was going to be a problem.

Yes, I know to get someone else to look at it, but since he's been good for the last 5+ years, let's assume he's telling the truth...

Is this something homeowners insurance does cover? Is there a type of insurance that does cover stuff like this? To rebuild the subtloor, I think he threw out a number like $4k.

Beyond everything else, it's the only bathroom in the house. How long should this sorta thing take?

Is there a way I can tell how precipitous the problem is? Is there a way to see if I have two weeks, two months, two years that this could still go on?

...oh yeah, I guess a subfloor is the part of the plumbing that is underneath the floor?
posted by Towelie to Home & Garden (11 answers total) 2 users marked this as a favorite
Dunno about fixing, but the subfloor is part of the floor, not part of the plumbing -- it's the even floor-type thing below the tile/linoleum/carpet/whatever -- probably some sort of plywood or something like that.

(can you tell I totally know what I'm talking about?.... but that might help a little)
posted by brainmouse at 10:50 AM on March 17, 2010

A subfloor is what's underneath the floor; it's not plumbing. For example

I had a carpenter put a tile floor in my bathroom last year; parts of the subfloor were a bit dodgy and were replaced, and this was part of a lot of other work so I can't put an accurate price on that but I don't think more than $1,500 went to the whole flooring job, tile included. I'm sure it could've stayed as it was for years had the previous floor not been ugly, too... I don't think the whole thing took more than two days, and I was not rushing things; with two people working it could've been a one-day job, I imagine.

I can't imagine that insurance would cover it. Houses get old, this stuff happens. But it doesn't sound like a big deal and $4k seems a bit rich, though I suppose a lot of that depends on where you live. Replacing parts of the subfloor here was just a matter of pulling up the old stuff and cutting new plywood to replace it. Not within my skill set, but also not something that costs a lot in materials or anything like that.

Ask your neighbours if they know a good carpenter/contractor type. If you like the plumber, ask him for a name.
posted by kmennie at 10:55 AM on March 17, 2010 [1 favorite]

I agree with the above. $4K is almost certainly a ridiculous estimate. This doesn't mean your plumber is being dishonest; he's a plumber, not a carpenter or handyman. Subfloor repairs are not his department.
posted by jon1270 at 11:04 AM on March 17, 2010

I discovered our subfloor was rotting when I punched a neat pencil-sized hole through the linoleum walking into the bathroom in high heels.

The subfloor is the layer(s) of wood (usually plywood laid on top of boards that rest on top of your floor joists) that's under your tile or linoleum. [diagram]. In bathrooms, the part around the toilet is prone to getting rotten if the wax seal at the base of the toilet leaks. The reason the toilet is wobbling is without firm wood for the foot of the toilet base to rest on, it's just balancing on top of the closet flange, which is about the size of a CD [diagram]. The more the toilet wobbles, the more likely the wax ring starts to leak and the more rotten the wood gets. As you can see in the linked photo, once the subfloor rots through, there's nothing down there but whatever is under that floor: either your basement, your crawlspace or the top of the ceiling of the downstairs floor.

You don't have to replace all of the subfloor if it's not rotten but fixing it is important as it doesn't get better on its own and the rot will spread. Fixing it will require determining how much subflooring needs to be replaced (crawling under the house should be part of this inspection; if you have linoleum you can check it yourself by trying to push a screwdriver through the floor moving away from the toilet), removing the tile/linoleum/hardwood/carpeting above the rotten areas, cutting out and replacing the rotten subflooring with new plywood and waterproof underlayment. Your current flooring is a loss unless it's tile and you have enough boxes of spare tiles hidden away somewhere.

$4k sounds way too expensive unless a) your plumber is assuming the entire bathroom subfloor has to be replaced or b) your flooring is an expensive-to-replace material. Get some bids from well-referenced contractors. It's a 2-3 day job for tile; any other flooring, it's a 1 day job. You'll be able to use the toilet for most of that time, but it will have to come out for a few hours during various phases of the job (note: the job goes much faster if the handyman doesn't keep having to reseat the toilet).
posted by jamaro at 11:14 AM on March 17, 2010 [3 favorites]

As some of the others mentioned, the subfloor is just the "floor under the floor". It's typically some type of wood. If that wood has been exposed to water, it can rot. When wood rots, it starts to quickly lose it's strength. It has nothing to do with the plumbing, other than if the plumbing, other than the plumbing leaking may have been the cause of the problem (and what caused him to notice it).

What type of floor is in your bathroom now? How big is the bathroom?

I replaced a rotted out subfloor in my new house last summer. It will typically involve removing anything in the bathroom (toilet, vanity, etc) and tearing out the floor. It was a small bathroom and I did it with myself and a couple of friends. It took a couple of days, but that was mainly because the demolition phase took longer than normal due to rotten wood.

If you house has a basement, you might be able to visibly inspect for rot. If not, does the floor seem more springy than in the rest of the house? A rotted floor will typically seems a bit bouncier than an intact floor.

This is most likely not an emergency repair that needs to be done immediately. However I am not a fan of having wet or rotted out wood holding my house together.
posted by PhillC at 11:17 AM on March 17, 2010

You'll want to get quotes from carpenters and/or general contractors willing to take on really small jobs. The final price could get a bit steep if you have to redo the entire floor, or if the rot/water damage has extended to the joists underneath. Your best case scenario is them only needing to pull the damaged sections and nothing else needing to be fixed, in which case $4k should pay for it several times over.

Be careful about mission creep, though. That's when you start saying, Well, since we are pulling up the floor anyway, why not install radiant heat, and redo the drain lines, and retile the bath, and move the sink, and and and. That's what will turn a small and cheap job into something expensive in a hurry.
posted by Forktine at 11:21 AM on March 17, 2010

Is there a way I can tell how precipitous the problem is?
Do you have a basement? Crawl space? The best way to see the extent and seriousness of the problem is to have somebody (who knows what they are looking for/at) get access from beneath the floor, at which point they can poke around and see the extent of moisture/damage/rot. It could be contained to just the subflooring (1x boards that run directly on top of the floor joists, or in newer houses, plywood/OSB), or you might have moisture issues in your floor joists themselves, which is a bigger problem (not a big deal, just more money).
posted by misterbrandt at 11:56 AM on March 17, 2010

We got new tile put in our bathrooms last year, and the flooring folks ripped out the plywood subfloor and installed cement backerboard in its place. You may want to consider this if you plan on spending a long time in the house.
posted by infinitewindow at 12:10 PM on March 17, 2010

We got new tile put in our bathrooms last year, and the flooring folks ripped out the plywood subfloor and installed cement backerboard in its place. You may want to consider this if you plan on spending a long time in the house.

I sure hope they replaced the plywood before installing the concrete backer. Backer board is great tile substrate, but it is not a subfloor or a substitute for one.
posted by jon1270 at 2:20 PM on March 17, 2010

$4K estimate is mental. It's possible that only the area immediately around the toilet drain has rotted, so you can just replace that area and then you're ready to install a new floor. Linoleum, vinyl and cork tiles need a layer of thin, fancy grade plywood or ceramic needs a layer of concrete backer boards.
posted by bonobothegreat at 2:40 PM on March 17, 2010

I've done this repair. You can see to some extent how bad the damage is by pulling the toilet, which costs only time and a new wax ring. But , really, I wouldn't recommend checking it out because it's easier just to start fixing it at that time. Worst problem is replacing the floor covering. If it's tile, it's a lot harder. Here's what's involved:

Pull toilet. Look at damage. Probably pull up the floor covering. If it's vinyl flooring, just pull it all up if it's a small enough room. If tile, be more judicious and hope you can find replacement tiles. Cut out damaged sections (probably with a reciprocating saw, maybe a circular saw). Buy 2x6 (or whatever is being used) blocking, and subfloor-rated plywood, and a wax ring. Install cleats/blocking so that all plywood flooring edges are supported (I suck at nailing, so I use hefty screws or brackets). Cut subfloor to fit and install (easier to nail, now). At this point the toilet may be temporarily installed if needed. Now, or later (if you put the toilet back in), you would install the flooring (vinyl is fast and cheap), and plop the toilet back down.

Maybe $50ish in materials. Less than a day for a pro, about a day for a non-pro. It's impossible to know how bad the damage is, but in my experience water damage is *always* less than you thought/hoped (don't ask me how I know this). I would not leave it longer than I had to; people have had toilets fall through the floor. There's really no way to know how bad yours is until you start.
posted by RikiTikiTavi at 4:06 PM on March 17, 2010 [1 favorite]

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