Leveling bathroom subfloor


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Old 10-25-04, 09:05 AM
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Leveling bathroom subfloor

i'm in the midst of redoing an upstairs bathroom in a concrete slab built house that's about 36 years old. the toilet, tub, vanity have already been removed. the original 1" square tile floor was laid on plywood. this underlayment consisted of two layers of plywood; the top one being 3/8" and the bottom 1/2". I've removed the top plywood layer which was confined to the bathroom with about 1/8"-1/4" gap between the ply and the bottom of the wall framing enclosing the room. the remaining 1/2" layer of ply runs beneath the wall stud plates, i presume the length of house.

about half the floor is level, and the other half not. the bathtub/toilet drain side of the room is not level and dips down towards the tub/ toilet drain side of the of the room. placing my flat edged 2' level in about the middle of the room, it rocks back and forth. if i move the 2' level towards the drain side of the room, the bubble shows the floor is not level and i have to lift one side of the level about 1/8"-1/4" off the underlayment to achieve level.
immediately adjacent to this side of the room is the master bathroom tub and toilet. both toilets share the same water supply and drain.

through a small access panel under the exterior soffet by the front door, i've already noted that the main drain placement required 1st floor ceiling joists surrounding the drain that are not 16" center-to-center. this was necessary, i suppose, to accomodate 2 toilet drains, 2 tub drains, 2 sink drains and water supply lines. i suppose as a result i have insufficient floor support on this part of the room.

i've noted that the drain side wall framing in the bathroom i'm working in is nailed directly into the 1/2" plywood subfloor which travels under the framing from one side of the house to the other. unfortunately, there does not appear to be any support (a joist or otherwise) directly under where the framing is nailed to the floor, at least by the toilet/tub drain portion of the room. in other words, the wall stud plate is held in place by nails that only go into the 1/2' ply.

i'm thinking that since there is no support directly under this wall framing that gravity and time have caused the drain side of the floor underlayment to drop. in fact, i can observe about a 1/8th gap between the top of the wall studs and the upper plate to which the studs are nailed.

the bathroom is directly above our front entrance hall.

i'm thinking that i have two options to achieve a level floor for 12" square ceramic tile:

option1: replace underlayment in its entirely down to subfloor and shim new underlayment to achieve level.

option 2: remove front entrance hall ceiling and affix new supporting joists so that i'll have level joists to screw new underlayment into.

of course, i would prefer option 1 to be a viable alternative.

any expert advice in this regard will be much appreciated.

by the way, this was quite a challenge to adequately describe my situation. if i've been unclear about anything, please let me know.

thanks in advance.

bob
 
  #2  
Old 10-25-04, 09:46 AM
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option 3???

just thought of a 3rd option...

with all bathroom floor underlayment removed and 1st floor ceiling joists exposed, fasten new level joists to nonlevel existing joists to achieve level floor objective. this would mean that it's not necessary to drop the 1st floor ceiling directly below the bathroom.

bob

bob
 
 

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