2 inch concrete slab over wood subfloor
#1
12-30-07, 06:56 PM
2 inch concrete slab over wood subfloor
Hello,
half my house is original 1906 old raised foundation with wood subfloor. In the late 80's they made an adition behind the kitchen on slab foundation. Basicacally since the house is on a slight incline, the addition was slightly higher then the original house, about 2 inches. So in order to avoid a weird low/high spot were the two foundation floors meet, and since a transition piece wouldn't adapt properly to the meeting point, they decided to level the kitchen floor to the back adition by pouring about 2 inches of concrete over the entire kitchen wood subfloor instead. Is this comon practice? The building inspector said it was no big deal, but everyone else seems to think that this puts to much weight on the old wood subfloor, and is prone to cracking. What would be another solution? would it be better to have raised the level of the lower kitchen floor with 2 sheets of 3/4 inch plywood and then finish it off with a thin layer of leveling concrete?
half my house is original 1906 old raised foundation with wood subfloor. In the late 80's they made an adition behind the kitchen on slab foundation. Basicacally since the house is on a slight incline, the addition was slightly higher then the original house, about 2 inches. So in order to avoid a weird low/high spot were the two foundation floors meet, and since a transition piece wouldn't adapt properly to the meeting point, they decided to level the kitchen floor to the back adition by pouring about 2 inches of concrete over the entire kitchen wood subfloor instead. Is this comon practice? The building inspector said it was no big deal, but everyone else seems to think that this puts to much weight on the old wood subfloor, and is prone to cracking. What would be another solution? would it be better to have raised the level of the lower kitchen floor with 2 sheets of 3/4 inch plywood and then finish it off with a thin layer of leveling concrete?
#2
12-30-07, 07:05 PM
How is the original floor constructed? 2''x6'' or 2''x8'' or ????
16'' on center or ??? What's the overall span of the floor? /Floor joists?
It all depends how well the original floor was constructed. Personally, I would have built it up with wood, (Actually did some of that with our house). but that would be more work i.e. more expensive.
16'' on center or ??? What's the overall span of the floor? /Floor joists?
It all depends how well the original floor was constructed. Personally, I would have built it up with wood, (Actually did some of that with our house). but that would be more work i.e. more expensive.
#3
12-30-07, 10:11 PM
the subfloor is old douglas fir strips, 3 inches wide and random leghts, suported by joists. The floorspan that is being built up with slab concrete is in our kitchen about 60 sf. If I decided to have the slab removed, and built up the diference with wood, would I still have to put a thin layer of some kind of leveling compound to make up for any difference? Also, what kind of wood did you use to build up your floors, plywood?
#4
12-31-07, 06:23 AM
I used plywood & luan. We had anywhere from a little to 1 1/2" difference in floors since the house has been added onto several times. In the worst cases I would put down the luan first and sandwich it with 1/2" or 3/4" plywood. I did have one spot in front of the office door that had a slight dip in it in about a 3-5' area. I used leveling cement there & then put plywood sub floor over it, then laid carpet. The biggest determining factor on load bearing would be how long the floor joists are between supports. Those old douglas fir joists are tough old pieces. The original part of our house is well over 100 yrs. old (Square nails). The rafters are true 2''x4'' douglas fir. After all these years there is no sag in the roof at all. I wouldn't want to cover that same span with the 2''x4''s we have available today.
#7
01-01-08, 06:08 PM
RE: GAry,
no, it was done in the 80's, the entire kitchen is built up with cement to match the level of the back adition. The joist are 4feet apart. I keep hearing people say that old doug fir is good for homes. But then again why does it seem so soft and scratch so easily when used for flooring?
The thing is the floors do seem to bow and creek at the joining point where the cement is. Maybe they were already bowing before, and the cement weight has nothing to do with it. But the built up slab in the kitchen has cracked, on the tiles on top have shifted. I'm conflicked as to just fix the cracks and leave everthing as is. Or, jackhammer the cement and level it the way you did.
no, it was done in the 80's, the entire kitchen is built up with cement to match the level of the back adition. The joist are 4feet apart. I keep hearing people say that old doug fir is good for homes. But then again why does it seem so soft and scratch so easily when used for flooring?
The thing is the floors do seem to bow and creek at the joining point where the cement is. Maybe they were already bowing before, and the cement weight has nothing to do with it. But the built up slab in the kitchen has cracked, on the tiles on top have shifted. I'm conflicked as to just fix the cracks and leave everthing as is. Or, jackhammer the cement and level it the way you did.
#8
01-01-08, 07:34 PM
Is there any crawl space room where you can get under it to shore it up? Maybe run a beam under the joists supported with screw jacks?
I had a wall between the living room & the bedroom (Since been removed to make it all living room) that had an old chimney built in it with a knee brace. The weight of that chimney over the decades put a 2''-3'' sag in the floor. I tried to jack it up but couldn't get it even. I ended up tearing all the flooring & sub flooring up and re-leveling each joist separately. Some I had to scab a sister joist onto, to straighten them out. It's all level now, solid & no creaks & squeaks, but it was a LOT of work.
I had a wall between the living room & the bedroom (Since been removed to make it all living room) that had an old chimney built in it with a knee brace. The weight of that chimney over the decades put a 2''-3'' sag in the floor. I tried to jack it up but couldn't get it even. I ended up tearing all the flooring & sub flooring up and re-leveling each joist separately. Some I had to scab a sister joist onto, to straighten them out. It's all level now, solid & no creaks & squeaks, but it was a LOT of work.
#9
01-02-08, 12:50 PM
yes there is a crawl space, but basically if I do jack it up, the 2 inch layer of leveling concrete wil crack. Basically I'm guessing that I have to start fresh, and remove this damb leveling concrete, straighten out the subfloor, and then level the kitchen out with the plywood like you did.
#10
01-02-08, 04:48 PM
Is the floor sagging bad or just minor cracks? You might be able to snug the jacks up under the floor, just to keep it from getting worse. Then patch the cracks. It's really hard to say without seeing it in person. Just thinking out loud. Hope it all works out for you.
Also, in addition to another water infiltration source, I suspect the aforementioned source has been flooding our dirt crawl space for several seasons and may have something to do with the large crack in the adjoining stem wall. What would be a good product to fill this vertical crack?
Thanks for taking the time to read my post and consider my questions
Howard