Leveling a really bad basement slab....

[Jeff Duncan]

OK I know the topic of leveling basement floors has been covered to death all over the net, the problem I'm having is it seems like all that info is for floors not really all that bad in the first place. How bad you ask? Well my floors drop almost 3" from the foundation wall to the lowest point about 6' away! Way to deep for self leveling compounds. Most of the concrete type products I can find are either for really thin to a feather edge, or really thick....no feather edge. So anyone know about options for going from 3"+/- to a feather edge? I don't want to use sleepers and ply if I can avoid it since there's little headroom already. Also haven't fully committed to a flooring, but probably tile.....safest for a basement in my mind anyway. Total area would be under 400 sq. ft..

Also don't want to have to bring in a "specialist", house isn't worth a huge investment and its just to have a play room for the kids and to move my rowing machine into....so I can still not use it, but in a nicer space:D

thanks,
jeffD

[Brian W Smith]

Had a 600 sq ft slab "ground" yesterday,for some fancy coating(business,not personal).Anyway,might have missed it in your post...have you assessed the "problem" in the structural sense?Meaning,what caused the issues and what's keeping them from getting worse?

[Mike Cutler]

Jeff

You would pretty much have to pour a slab on top of the slab and get everything to less than an inch and then try the self leveling compound, unless you're willing to lose some headroom and do the whole slab to a minimum thickness.
How much headroom do you have now? Either method is going to take away headroom, it's just a matter of how much.
You're looking at a lot of work no matter which way you go my friend. To pour a slab, on top of a slab, there are a lot of prep steps, a few special tools and machines, and some somewhat nasty chemicals involved. Then comes the tile work. BTDT ;)
Have you looked at something like Dri-Core on top of sleepers? A Co-Worker used their system, available at Home Depot, for his basement, and it came out pretty nice. His floor wasn't as bad as yours but it had also a downward slope and had rolls in it. This method would not include any tiling at the end, so there would be a 3/8" height savings.

[Malcolm McLeod]

Jeff, ~22yrs ago my in-laws incorporated a 15'x40' covered porch into the conditioned space of their lake house. Porch had original ~3-4" slope for drainage, and was levelled with a self-leveling underlayment, basically a fly-ash product. It was done in a single lift/pour, and then ceramic tiled. House was sold a couple of years ago, but I know of no issues with the floor to date. ...So, it can be done.

Couple of items may have contributed to their success: 1. House was slab-on-grade construction and both house and porch were part of monolithic pour; 2. Southern, sandy, and stable soil, so nothing was moving or heaving.

[Jim Becker]

Jeff

You would pretty much have to pour a slab on top of the slab and get everything to less than an inch and then try the self leveling compound, unless you're willing to lose some headroom and do the whole slab to a minimum thickness.

This is very similar to what I was going to reply if you're going to stay with the hard/concrete floor. If it's going to be living space, you could custom cut wedge sleepers to level and then insulate and install a wood subfloor on top of the sleepers.

[Jeff Duncan]

Thanks guys!

Ok so as to what caused the problem.....no idea. The house is not new, so it's been like this for a very long time. Also the PO apparently had a lot of work done in the basement as the house was sinking in the middle. So there was a lot of concrete added at that time. At this stage I don't think it's going to move a whole lot more. But you never know.

As for ceiling height.....at the highest point in the floor it's roughly 6-11", which is also about average for what the rest of the basement is. That's the part that stinks, the area I have to work with is the worst part of the basement floor. In fact I just measured and it may be even more than the 3" I thought!

I've seen those Dri Core tiles and combined with flooring on top they would eat up a lot of headroom. I'd go sleepers before those, but I'd rather not do that either. Truth is I'm not a fan of wood on the floor of old basements. All you need is one pipe to leak, a water heater to go, anything, as all water heads down to the lowest point....and that's the basement floor! So having any kind of wood on the slab thats not PT is just invitation for problems.

So if I had to pour another slab anyone know what's the minimum thickness? If it could be say an inch, that wouldn't be too bad. But if it needed to be say 3" now it's easier to use sleepers. Also who should I look for to do this type of work? If I could do a small area I'd do it myself, but don't think I could handle pouring several hundred sf of slab in a shot. Would I call a tile guy or a mason?

thanks again!
JeffD

[Neil Gaskin]

You should call a concrete contractor. I do not believe a tile or mason contractor are a good fit. The only way to fix this properly is to remove the old slab and pour a new one. There is not a good solution for going from 3 in to nothing.

Self leveling products are designed for minimal height varience and pouring new concrete to anything less than 3 in is going to crack up and fail. You could try a highly fiber Reinforced concrete but even that will not likely work and will not bond well to the old concrete.

Cost should not be to much more than a "repair" and you can address the sub grade issues that caused the problem.

[Bill Jobe]

I watched a home improvement show once (This Old House?) and they were dealing with a similar situation. They brought in a company that used a process similar to mud jacking but instead they used liquid foam insulation and pumped it under very high pressure until the floor was level. An added benefit was that the process raised the floor temperature by about 10F.
Costly, no doubt but great idea.

[roger wiegand]

It might be cheaper, easier, and with a much better result to jackhammer it out and re-pour the slab correctly, including a good gravel substrate, piping for french drain/radon mitigation, and insulation while you're at it. If your basement is a walk-out it wouldn't be too bad a job; if the old material would need to go out via an interior stairwell then probably not such a great idea.

[Al Launier]

As a DIY project would renting an electric jack hammer to remove the high area(s) & then pour a minimal layer of concrete be an acceptable alternative? That would establish level & minimize impact to head clearance,.

[Sam Murdoch]

I don't know Jeff - but if I were doing this, the PT sleepers sounds completely acceptable. Really how many floods do you expect in your house in your time there? PT sleepers with or without insulation between can be dried out pretty thoroughly with dehumidifiers - if it ever came to that. 3" in 6' is a huge drop but cutting tapered sleepers with a track saw is a cinch. Then you can apply a good sub floor and whatever finish you like with no fuss.

Yes - I have sleepers on my slab with insulation in between and yes I did have my 100 year flood - SuperBowl 92. An on demand water heater (not properly installed on that level) froze and burst. Had 2" of water over a 35' x40' area before I noticed the problem. Lots of scrambling with wet/dry vacs and a week of dehumidifiers working full bore got it all dried out. NEVER a sign of mold or mildew or any residual effects at all in the short term or to this day.

Otherwise I'm thinking take out the old concrete and/or simply pour new. Holy smokes - the 1st is heavy loud and dirty work. Don't know how thin concrete can be poured. In my part of the country tile guys would be way out of their league with this kind of work - you would need a foundation guy. Good luck how ever you proceed.

[Steve Peterson]

It might be cheaper, easier, and with a much better result to jackhammer it out and re-pour the slab correctly, including a good gravel substrate, piping for french drain/radon mitigation, and insulation while you're at it. If your basement is a walk-out it wouldn't be too bad a job; if the old material would need to go out via an interior stairwell then probably not such a great idea.

If you go through this solution, is it possible to dig down a few inches to gain a bit of ceiling height? You would have to dig some dirt out to put in gravel.

Steve

[Jim Mackell]

I'd certainly drill a few test holes to see how thick the slab is. Many of the old time floors were only and inch or so. Might be really easy to take out, deepen and repour.