weakened wood subfloor over a concrete slab...


  #1  
Old 12-22-04, 12:41 PM
Salieri
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weakened wood subfloor over a concrete slab...

Hello
I have a brick building with three apartment units in it.
The lower unit is about 2-3 feet below grade, the floor in this unit is a wood floor, or subfloor rather, finished with resilient tile and carpet, built over a concrete slab.
Damage over the years(it is a 80 year old building) has lked to some areas of the floor being very weakened and collapsed. Termites caused much of this old damage and a new batch of them have to be dealt with this year again.
Most of the units floors are intact but a bit springy.
The unit was an old dental office and I am using it as such now. I will not be here for more than 5 years , when the building will be sold. The new owneres, if they folloe the trend in this neighborhood, will renovate this floor to use as a residential unit. I need to dress the place up with new tile and flooring.Question: Can i reinforce the flooring areas that are not too bad by simply laying plywood 3/4" or cement backer board down to stiffen up the existing floor and then finish the floor over that? I know this will necessitate new baseboard and moldings and door casings but that will be done anyway. Tp rip up the entire floor and place new joists(it is about 4-6 inches of space beneath the floor now0 is not a project I would like to do.
What do you think?
Thanks.
Salieri
 
  #2  
Old 12-23-04, 10:01 AM
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Hello Salieri and welcome to the forums!

Considering the termite damage you've referred to I think it would be best to rip out the subfloor, framing, everything down to the original concrete and replace it. The framing should be treated lumber since it's in direct contact with the concrete and for tile this should be framed up on 16" centers and then covered with two layers of 5/8" ACX plywood at the least if you intend to put down ceramic or stone tile. I would add 1/2" cbu over that as well if possible or else use a ditra membrane under the tile.

Problem I see with trying to simply lay plywood over the existing flooring is that the framing beneath has been weaken presumably from insect (termite) damage, so you just laying good material (and $$) over bad, not a good or logical decision IMO.

Guess that's my $.02 worth on this subject, only thing I would add as a point of fact, cbu isn't structural and adds no structal support to the mix, plywood is and would stiffen things up, but only for a short period of time.

HTH and Happy Holidays! :glocke:
 
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Old 12-23-04, 12:46 PM
Salieri
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ok then.. thanks for the advice on this..
i will pick and choose the areas that I will rip up and try to keep it to a minimum...
 
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Old 12-24-04, 03:04 PM
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Sounds like a better idea, any of the joists which are damaged should really be replaced with new treated lumber. Then what you might also think about once the framing is dealt with and you patched in the subfloor directly above the repairs is to just cover the entire thing with a single layer of luan underlayment, Glue & screw that down and you could install carpet or vinyl tile over it without a problem. Like I said before, if you were wanting to redo the floor with a ceramic, porcelin, or natural stone tile, the subfloor would need to be beefed up more.

Good luck & have a good holiday!
 
 

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