Basement floor cracking

[Bryce]

House-hunting: Saw a ranch built in 1997. Basement floor is concrete, scored into approximately 12-foot squares. The slab has cracked along each score and the cracks opened up to 1/8-3/16 inch wide. There is no evidence of vertical displacement across the scores. Are cracks this wide normal? Due to shrinking of concrete during curing? Or?

I could see sand laying on some of the crack edges. There is a sump pump, so maybe a pump failure led to water rising under the slab and washing sand upward through the cracks. If this were my house, I'd caulk the cracks with a good silicone sealant ... or maybe that's a bad idea.

We chose to continue shopping for a house. This will be our first house with a sump pump. Should I be concerned about a basement floor like this?

[Tony Miklos]

I'd worry about it needing a sump pump and wouldn't worry about the cracks.

[RicodJour]

The scores in the slab are called control joints. They control the inevitable cracks that occur in concrete, and insure that the cracks are not running across the slab randomly. This is a good thing.

If you were to use a sealant in the cracks, you would not use silicone. A self-leveling polyurethane sealant is the standard, though any good quality polyurethane caulk would work.

The sump failure is a conjecture, as would be any remote diagnosis of the situation.

R

[Vic Smith]

Just walk away. A cracked up 14 year-old basement floor is just bad news. Don't let anybody tell you what you saw is "normal." If it was, why are you even mentioning it? Your instincts are working. You're house hunting. How many cracked basement floors are you seeing?

--Vic

[Frank]

I'm not a sump pump fan. Often when you need it most, during a storm, power goes out. Woman down the street had her's on battery back-up but it failed too and she got maybe 3 inches of water in her basement.

Also have neighbors near her that hit a spring in digging foundation and their sump pump runs constantly.

When buying a house you should always look for water marks in basement. Also important to look at straightness of walls as a buckled wall could be a failure in the future.

With today's real estate "buyers market" there is plenty to choose from.

[millinghill]

Cracking along 14yr old control joints is ok. Cracking along EVERY 14yr old control joint is... still kinda ok, but peculiar. Sand along these cracks is probably bad. I can speculate that the groundwater pressure was so great as to overwhelm any (existing conduit?) or overland route to the sump such that water started welling up wherever it could (i.e. every crack on the floor). Look for water marks on the wall or on the side of the furnace/ boiler. Look to see what, if anything, the current homeowner stores in the basement. Look at the lay of the land and see if you could install (at significant future cost) a perimeter foundation drain that would flow via gravity to daylight so that you needn't rely 100% on electricity and a sump pump.

When we were house hunting, the BEST days to go were the rainiest. One guy (across the street from a pond) was wet-vac'ing his immaculately clean basement floor that was taking on water at the wall/ floor interface as we were standing there; and he had to nerve to say, "This never happened before!" We walked out faster than our realtor could keep up with us.

A sump pump shouldn't be THE deal breaker for a house. You just need to have a plan of what to do when it fails. That plan can be to have a generator, to have a battery backup, to have a spare pump, or to just let the (hopefully unfinished) basement flood. Your choice.

Theodore

[hrhofmann]

I just installed a water-jet back-up sump pump, in addition to the two pumps already in the pit. My wife didn't get the generator started quickly enough at the last power failure and I was out of town. Battery back-ups have not been powerful enough to last the length of some of our outages.

[RicodJour]

You really felt it necessary to lay the blame on your wife? Perhaps she was too busy celebrating you being out of town to care much about the house.

R

[Bryce]

Thanks to all who responded. Great advice is always available here!

I added what I have learned from your comments to my checklist that I take to each house-hunt visit. I steer my SO and the real estate lady to the basement early on in a visit. For me there's lots to learn down there.

Again, thank you!!

Bryce

[Colbyt]

Frankly, I would worry more about any house with a basement that did not have a sump pump.

How frequently it is used is a valid consideration but having one is not.

[Tony Miklos]

I'd much rather have a natural gravity flow drain then rely on a sump pump. To each is own.

[aemeijers]

6-7 years ago when I was house shopping and hitting the Sunday open houses, I never even let the realtor start their canned pitch. My first question was 'where is the basement door?'. Lots of times I didn't even bother to look at the rest of the house, if I saw dealbreakers down there. Most realtors are either clueless about construction, or they are damn good actors. I pointed out a badly-hidden-by-paneling bowed basement wall to one, and then took her back upstairs to show her the frost-heaved front porch that had caused it via ponding and hydrostatic pressure, and her eyes got so wide. IMHO, training for a realty broker license, or even the 'Realtor(c)' trade name privilege, should include how to do an actual house inspection.

But there are fools out there. Looked at one place where the floor system was 2x6 joists over a forest of screwjack poles, but they had remodeled the hell out of the upstairs, which looked very nice. But the place did sell, a couple weeks after I looked at it. Whatever loan officer wrote paper for the place should have been fired.

[Colbyt]

I completely agree with your statement but that is often not possible with a pit basement.

[aemeijers]

Shrug. My sump pit has cobwebs in it, and no pump. In 6 1/2 years, any basement wetness issues I got from time to time come from ground level outside, and I (knock on wood) have fixed most of those problems with a shovel, and pulling the downspouts out of the straight-down-but-connected-to-nothing pipes idiot previous owner put them in. Where did he think the water was gonna go? He KILLED the footer drains, if they were ever there, by filling in the notch in front yard where driveway used to be, leading to the now-useless closed off original basement garage bay.