Home>Discussions>BATHROOMS>Rotted subfloor and NO subfloor - bizzare!
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Rotted subfloor and NO subfloor - bizzare!

Subfloor around apron/edge of tub rotted (see photo). As it stands now I ripped out that portion of the subfloor and there is 1/2 inch gap between the apron edge and joists.

The 1/2 inch subfloor only extends 8 inches inward/under tub on each long side.

There is NO subfloor in the middle underneath of the tub!

I am trying to convince my husband that it is well worth getting rid of this ugly yellow tub and putting a 3/4 inch subfloor as required and a subsequent new white tub.

Why would there be no subfloor? Did they not do this in 1967?

Re: Rotted subfloor and NO subfloor - bizzare!

I would remove the tub, the rotted wood, remove any rotted drywall, inspect the studs and joists (if your bathroom is on joists), replace any damaged framing member, clean the rest and start from scratch.

Your minimum subfloor thickness required can be easily determined following the deflection formula that can be found on john bridge tile forum.

Why there is no subfloor under tub is not important at this point. Maybe they wanted to save a couple of dollars, maybe they ran out of plywood, or the framers left access opening for plumbing purposes. You will subfloor the entire bathroom, allowing enough space for a plumber to do his connections. A tub has to sit on a solid subfloor plus an horizontal ledger before you can hook up the drain line.

Re: Rotted subfloor and NO subfloor - bizzare!

Thank you. Due to your post and another post on the John Bridge Tile forum I have been able to convince my husband that we should demo the whole thing.


MLB Construction
Re: Rotted subfloor and NO subfloor - bizzare!

many, many, many older houses do not have a subfloor under a cast iron tub. sometimes i've seen the sub floor butted up aginst the tub skirt and other times there is 1"-2" of sub floor going under the tub skirt. yes, sometimes tubs were just resting on the joists. there's nothing really wrong with this practice that i'm aware of, i guess it's just the way they did things for ease of plumbing. obviously the wall side of the tub has to have a ledger board attached to the studs. if i were redoing the bathroom and tub, i would install a subfloor. if the tub was going to stay and not be replaced, i would leave it as is.

MLB Construction
Re: Rotted subfloor and NO subfloor - bizzare!

the more i think about it, maybe they started putting subflooring in for fire stopping or heat/cold transfer from a unheated basement.

Re: Rotted subfloor and NO subfloor - bizzare!

Great post!
Thanks for sharing.


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