Concrete basement floor - advice? - PeachParts Mercedes-Benz Forum

cornblatt · #1 06-07-2009, 08:40 PM

I have a concrete basement floor that is ~95 years old. It resembles the surface of the moon; it's lumpy and uneven. The 'craters' range in diameter from 1" to about 1', and their depth is between 1/2" and 3/4".

In addition to being unsightly, it's impossible to keep clean because the pits trap dirt and little bits of concrete grit, and it is not pleasant to walk on. I would like to smooth out the surface to address these issues.

The local concrete specialty shop recommended a self-leveling compound (this one: http://www.mapei.it/Referenze/Multimedia/NovoplanEasy_TDS_EA.pdf) but it is $24 per bag, and I'd be lucky if a bag will do more than 10 square feet. For an 800sf basement, that's about $2000. Plus, the floor is not level from end to end, so when I dump in the $2000 worth of leveling compound, it may all end up in one corner of the room. And, it doesn't appear to be marketed for use as the final floor finish; they say it is just an underlayment. The products that are marketed as a final floor finish are twice the price. So, I think this is not an option for me.

Someone else suggested that I make my own sand mix (1 part portland cement, 2 to 3 parts sand) and just trowel it on. This would be less expensive, and the surface would only be as good as my troweling abilities, but it would probably do the job. I am not sure if it would be strong enough in areas where it is thin though - I don't want it flaking off if it doesn't bond well to the existing concrete.

I'd also like something that provides a bit of a moisture barrier (it's not damp to the touch, but if you leave a cardboard box on the floor for a week or two, the cardboard gets soft). A third person told me that there is some sort of penetrating sealant product you can paint on, but they didn't recall the name of it.

Do you guys have any thoughts or ideas on how to tackle this project? I don't want to spend a lot of money on it (a few hundred $ max) because the basement is dumpy and only used for storage. The ceiling is too low to ever turn it into a usable living space.

Hatterasguy · #2 06-07-2009, 08:53 PM

I'd paint it with some epoxy basement paint and call it good. Thats what I did to an old house I sold last fall, it came out pretty good. Cost me $150 and a days work. Roll it on heavy, don't be shy.

The only way to really fix it is a ton of work. Jackhammer the old slab out and pour a new one. My uncles partner did it once on a house in West Haven, its horrible work.

If you get water in the basement, no paint or sealer is going to fix it.

t walgamuth · #3 06-07-2009, 09:08 PM

The dampness will make it tough to get paint to stick I think.

Although its a lot of work I would advise breaking out the old concrete, leveling the earth, putting down visqueen vapor barrier and wire mesh and pouring a new floor.

If that concrete is really 95 years old (I doubt it) it will probably break out pretty easily. Get a large pry bar (6' or so) and start in a soft spot and just get under the slab and pry.

You will spend mostly labor here but you will get a new floor and a vapor barrier. It will add value to the house too.

mpolli · #4 06-07-2009, 09:22 PM

I wonder how much to grind it smooth? That's a pretty big area. You might get a quote on busting it out and repouring. I don't think I'd want to do that myself.

t walgamuth · #5 06-07-2009, 09:42 PM

Quote:

Originally Posted by mpolli

I wonder how much to grind it smooth? That's a pretty big area. You might get a quote on busting it out and repouring. I don't think I'd want to do that myself.

I bet it would cost more than digging it out and replacing all the concrete.

Hatterasguy · #6 06-07-2009, 10:12 PM

Quote:

Originally Posted by mpolli

I wonder how much to grind it smooth? That's a pretty big area. You might get a quote on busting it out and repouring. I don't think I'd want to do that myself.

Probably to thin, those old slabs are often skim coats. Concrete is heavy when doing it by hand. So the old guys often cheated, at least from what I have seen.

Can you get a cement truck close enough to pour it? Can they get the shoot in? Mixing that much concrete is for the birds, buy it by the yard off a truck. Its not that much.

Just remember the trucks weigh 80k pounds, so they will do some damage to your driveway, like break it into ruts...

Its a horrible job, so I would pay someone to break it up and shovel it out. Than load it into the dumptruck with the backhoe myself. I wouldn't dig out much, since you could undermine the footings. Just lay down some plastic and rebar and pour a new 4in slab. Pouring concrete sucks, I'd have our concrete guys do it.

pawoSD · #7 06-07-2009, 09:27 PM

I'd bust it up and re-pour (myself)....might be icky work, but the smooth nice end result would make it all worth it.

jt20 · #8 06-07-2009, 09:43 PM

dry-loc is one of those sealant /paints.

Personally, if I wanted to finish the floor in the future, I would set up a matrix of level strings across the floor and determine my high and low spots with respect to the overall tilt of the entire floor. If the entire floor has a natural slope to it... leveling it is out of the question.

But this would help you do what T Walg. suggested: Take out the high spots, and fill in the low spots according to what your future plans are. If all you want is to paint it, getting one that sticks will make cleaning the floor and its imperfections much easier.

cornblatt · #9 06-08-2009, 01:03 AM

Thanks for all of your comments and ideas! You guys are great!

It's a rental property, which adds a lot of constraints to the decision making process. I should have mentioned this earlier but I didn't think it was important when I made the original post.

Quote:

Originally Posted by t walgamuth

Although its a lot of work I would advise breaking out the old concrete, leveling the earth, putting down visqueen vapor barrier and wire mesh and pouring a new floor. It will add value to the house too.

Quote:

Originally Posted by pawoSD

I'd bust it up and re-pour (myself)....might be icky work, but the smooth nice end result would make it all worth it.

If I lived there myself, then yes - I would definitely be chipping up the floor, digging down another foot (ceilings are currently 6'7"), and pouring a new slab.

But, as a rental, I would never recover the cost of a project like this through rent, and the scope of the project is also limited as I don't want to disrupt my super-nice tenants any more than necessary (in terms of time and mess/destruction). If I was to sell the house, it's likely that it would be torn down to build something new, so anything I do won't really add resale value to the property.

If I had more time/money, this would be the right thing to do though.

Quote:

Originally Posted by MS Fowler

Why not place a wooden floor, ( 5/8" OSB) over a 6 mil poly vapor barrier right over the concrete? You could use 2X4 as joists to let you shil it level if you want. Leave the concrete like it is.

It's actually too lumpy to put plywood on - truly the worst concrete job I've ever seen. The basement ceilings are low as it is (maybe 6'7" to the bottom of the floor joists for the main floor) so I can't go over top with anything thicker than about 3/4"; putting framing underneath to level it would be too thick. The furnace, hot water tank, etc. are also sitting on the existing floor and would be buried if I add anything with substantial thickness.

Quote:

Originally Posted by jt20

dry-loc is one of those sealant /paints.

I will look up the dry-loc product - thanks for the tip. Your matrix-of-strings idea is a good one - I will do that tomorrow night just to get an idea of how bad it really is.

Quote:

Originally Posted by Hatterasguy

What are the basement walls made out of in this place?

The foundation walls are poured concrete as well. The house was built in 1912. I'm not sure if it's true, but I've been told that it was common at that time in this area for them to make the concrete using the sand / silt they obtained from digging the hole for the basement (the house is near a river and once you get down 2' the soil is very sandy). It's not quality concrete by today's standards, but it holds the house up. Neighboring houses have crumbly foundation walls, so I think I got lucky with this one. The concrete on the floor is only about 1" to 1.5" thick (just a skim coat, like you said).

My goal is to turn the basement from a negative feature of the house into a neutral one with minimal expense / time commitment... it just has to be clean looking so that the tenants aren't creeped out by it.

The cost and time restrictions have led me to the idea of topping it with something (e.g. self leveling compound or sand mix as I mentioned in the original post, with a primer/bonding agent applied first to the existing floor), but I'm not sure what the best option is or if there's something else I should consider.

Thank you again for all of your ideas! I have to come up with a plan by the end of next weekend, so if you think of anything else, please let me know.

kerry · #10 06-08-2009, 09:07 AM

Quote:

Originally Posted by cornblatt

It's a rental property, .

In that case, just leave it alone. It's been there for a hundred years and can stay there until you're long gone. If you're worried about what your tenants think of it, lock the basement door and keep them out. I've got rentals with dirt basements.

Hatterasguy · #11 06-08-2009, 08:02 PM

Quote:

Originally Posted by kerry

In that case, just leave it alone. It's been there for a hundred years and can stay there until you're long gone. If you're worried about what your tenants think of it, lock the basement door and keep them out. I've got rentals with dirt basements.

Oh I didn't see that part. Screw it than don't waste the money.

Only clean it up if you plan on selling it.

TMAllison · #12 06-08-2009, 08:33 PM

I'd go with a topping from someone like Ardex or equalivent. They have products that aren't self leveling too and that are designed for 1" type fills.

Another option would be to speak to your local concrete plant and see what mix designs they have for a 1" topping pour. Bonded, it should work fine if the original is dimensionally stable and free of contaminants. I once did a 3/4" concrete topping over visqueen, over slabs on as well as above grade which was used as a temporary pedestrian traffic surface until I could get some special order slate hand sorted in India to do the job to the silly owners satisfaction. Even though it was an unreinforced, floating topping it was still in reasonable shape 9 mos later when we demo'd it and tiled it.

Chas H · #13 06-07-2009, 09:55 PM

Talk to your local concrete mixers. There are smooth flowing, self-leveling mixes for radiant heat floors that may be applicable for your case. And be very careful about removing a basement floor as it likely stabilizes the foundation; in fact the floor may well be part of the foundation.

t walgamuth · #14 06-07-2009, 10:06 PM

If that floor stabilizes the foundation heaven help that foundation.

If you can explain how to pour a foundation and floor together I would appreciate it.

Chas H · #15 06-07-2009, 10:12 PM

Quote:

Originally Posted by t walgamuth

If that floor stabilizes the foundation heaven help that foundation.

If you can explain how to pour a foundation and floor together I would appreciate it.

The house is 95 years old for starters. Who knows how it was constucted.
Have you never heard of a raft foundation. You can do the search.