Basement Sub-Floor Using Sleepers - Need Some Pointers

[CHDinCT]

So I'm soon to start on putting a sub-floor over my poured basement concrete slab. The house is 25 years old and we've never had leaks or standing water in our basement, but we have a LOT of dampness and get a lot of efflorescence, and the slab get a mottled look (blotchy dark areas), so I want to cut down on the dampness and avoid tracking that white power all over our upstairs hardwood floors.

I've gone back and forth on how to do it, using either PT sleepers over 6 mil plastic, then 3/4" T&G subflooring glued and screwed, or those dricore 2'x2' squares. I've done a search here and saw some other products mentioned, but none of them seem to be sold anywhere near me, only the dricore product. My problem with using dricore is that the concrete floor is very uneaven and I would need 6-10 bags of floor leveler first. Dricore can be shimed, but only up to 1/2" per the spec's I've seen, and I have some places that are over that. Plus, using cedar shims to level the sleepers would be a whole lot cheaper and faster than floor leveler I think. Also, about 20 years ago, I tried to cut down on the dampness by putting down a product called Thoroseal (normally used to seal concrete walls), then putting epoxy paint over it - didn't work and most of the Thoroseal flaked off over time, but not everywhere). So I'm not sure I can get a good bond using floor leveler.

So assuming I go with sleepers my questions are:

- Is 2' on center, with Styrofoam in between enough, or do I need to ge 16" OC like normal wall/floor framing?
- Planning on using a Ramset to nail the PT sleepers down, but I read somewhere that they tend to deflect if there's any space between the board and floor. Will I have any issues shooting them through 1" PT and say up to 3/4" of shims? Never used a Ramset so I'm not sure what to expect.

Any other rec's are welcome as well. Thanks

 

[Cord]

Honestly, it sounds like you have moisture wicking through the slab. I'd be afraid of creating a mold issue by over framing the floor. Would you be willing to use a ceramic or porcelain tile?

 

[CurlyDave]

I would be more concerned with the nails the Ramset shoots being properly galvanized for the pt sleepers. Today's pt is a lot more corrosive than many people realize.

 

[ace10]

I put down 2X4 PT sleepers under my basement floor. I don't have any moisture issues whatsoever, but wanted a softer floor under foot and also the option of using real wood flooring.

I didn't use any plastic.

Shot all the sleepers into my 12 year old slab. It was no easy task. Expect to use hot loads in the .25 cal gun. Driving the ringed 3" nails coated for PT direct contact.

I did not shim the sleepers, instead I actually planed each one down according to the pitch of the slab. Which was an absolute time suck. Crazy, crazy, crazy amount of effort. Around the sump, I had to shim the joists up a bit, and yes, the nails did want to deflect a bit. Maybe 25% of them gave me trouble.

I used Polyiso ridgid insulation between the joists. 3/4". Used scrap strip of the insulation to pad the sheet out to flush with the top of joists.

Glued and ring shank nailed the 3/4" decking to the joists.

Joists were 16" on center. Probably could stretch them out to 24" OC given the 2" extra width of the joists. Maybe compromise and go 20"?

 

[merlynr]

Check into cork tiles. I think they can be snapped locked onto a concrete floor with the recommemded vapor barrier. If something would happen and you have a moisture problem in the future you can remove them and dry things out and you're good to go again. I put them in a basement room in place of an old carpet and they are nice to walk on and they are organic from a cork tree.

 

[CHDinCT]

Honestly, it sounds like you have moisture wicking through the slab. I'd be afraid of creating a mold issue by over framing the floor. Would you be willing to use a ceramic or porcelain tile?

Yes, definitely have moisture coming through but no standing water. I put in an industrial dehumidifier that pumps itself out last year to see if that would solve it but as expected, it only takes the moisture out once it evaporates into the air. I was thinking the plastic would stop 98% of the moisture migrating through the slab. Going to talk to a neighbor who did the same as I'm planning years ago, but I don't know how much moisture he had in his basement.

Tiles would definately require a lot of floor leveling. I think the concrete guys must have been drunk the day they poured my basement slab. Plus the Thoroseal I applied was left rough in a lot of spots (wasn't thinking about finishing the basement back then).

 

[CHDinCT]

I would be more concerned with the nails the Ramset shoots being properly galvanized for the pt sleepers. Today's pt is a lot more corrosive than many people realize.

Good thought. I will check to see if the nails are rated for today's PT (ACQ?)

 

[CHDinCT]

I put down 2X4 PT sleepers under my basement floor. I don't have any moisture issues whatsoever, but wanted a softer floor under foot and also the option of using real wood flooring.

I didn't use any plastic.

Shot all the sleepers into my 12 year old slab. It was no easy task. Expect to use hot loads in the .25 cal gun. Driving the ringed 3" nails coated for PT direct contact.

I did not shim the sleepers, instead I actually planed each one down according to the pitch of the slab. Which was an absolute time suck. Crazy, crazy, crazy amount of effort. Around the sump, I had to shim the joists up a bit, and yes, the nails did want to deflect a bit. Maybe 25% of them gave me trouble.

I used Polyiso ridgid insulation between the joists. 3/4". Used scrap strip of the insulation to pad the sheet out to flush with the top of joists.

Glued and ring shank nailed the 3/4" decking to the joists.

Joists were 16" on center. Probably could stretch them out to 24" OC given the 2" extra width of the joists. Maybe compromise and go 20"?

Thanks for relaying your experience. I'm looking at a 27 cal. semi-automatic gun and thinking of using 1x4 sleepers so I was hoping to only need 2.5"
nails. It looked so easy watching Youtubes of people shooting nails into concrete, but as usual, it's just never that easy. Like you, I may need to shave a few boards down if I hit a few unexpected high spots. Spent some time with a few levels and a string line to try to find the highest spot, so I could work out from there - don't have one of those fancy rotating laser levels. If I use rigid foam insulation (Owens Corning Foamular) I was thinking 2' OC would work since the floor won't actually span any voids (well theoretically anyway).

 

[CHDinCT]

Check into cork tiles. I think they can be snapped locked onto a concrete floor with the recommemded vapor barrier. If something would happen and you have a moisture problem in the future you can remove them and dry things out and you're good to go again. I put them in a basement room in place of an old carpet and they are nice to walk on and they are organic from a cork tree.

Hmm, didn't think of that. I will check it out, but I may still need to level the whole area first, but maybe not if they're flexible enough. Thanks

 

[JimRB]

The pourable floor leveler is some pretty neat stuff. I have used it and have watched "pros" use it. Personally I would rather pour than shim, and do tile afterwards. That moisture coming up concerns me for any floor covering that supports mildew.