Half crawlspace half concrete slab?? Any advice?

Question

Bought a house in probate recently for a good price. It appeared that about 30% of the crawlspace under the house was inaccessible. Theory was there was a hatch under the carpet somewhere that could get you in, but didn't know where.

I have corrugated pipes that have rusted from the inside so there's very low water pressure in the bathrooms due to the rust buildup. Plumber recommended replacing them completely with PVC. Today I had a contractor try to cut a hole into the inaccessible crawlspace area but turns out there is no crawl space!

The house was built in 1958 and after laying all the pipes for the two bathrooms, they filled that part of the house up with some dirt and poured concrete on top, then put the floors on top of that.

Has anyone else been in this kind of situation? Any recommendations would be most appreciated.

I spoke with a friend with a lot more experience in construction than I have and he suggested renting a jackhammer to bust all the concrete up, have the plumbers do what they have to do, and turn it into a crawlspace so it's accessible going forward.

Marshall Downs · Answer

Could be grade beam construction, but I doubt it would have a concrete floor if that was the case. My bet is it's a slab.

You can probably get a good idea of the design by determining where the foundation and block wall meet in relation to the interior floor. If it's a very similar elevation, that would indicate that it is a slab. If the floor is higher than the bottom of the block wall it is probably a crawlspace.

Patrick Liska · Answer

sound like a normal slab on grade. have the floor cut and replace the galvanized pipe with PEX, but run it through some schedule 40 pipe, maybe 3". this way if it ever has to be removed it can be cut, pulled out and new one pushed back through. i do not recommend running the pipes through the attic, i'm sure Georgia doesn't get that cold, but something may happen to the lines if they are up in the attic and cause more damage below. plaster walls can be patched. while you are at it check the waste lines, if they are cast iron, check the condition and replace if you can, that would be the time to do it.

Russ Smith · Answer

It's really hard to visualize the layout and your scenario without having photos, etc. but depending on how things are configured (incoming water line, water heater, etc.)  you could consider having a plumber quote you a re-pipe for both the hot and cold side for the two bathrooms.

I've had re-pipes done by dropping new lines down through the walls and running pipes through the attic.  Obviously there will be some drywall repair but if you get a plumber that knows what he's doing, the drywall damage can be relatively minimal.  You could at least compare the cost of a re-pipe vs. busting up concrete and then you still won't have access to the pipes should you have a future issue.

JD Martin · Answer

I've never heard of this and I've seen a lot of houses. But nothing would surprise me. If it were built into a crawl space, I would excavate and turn it back into a crawl space for the simple reason that you would have wood floor joists if it was built that way, and you don't want dirt piled all the way up to the joists. This is independent of running new plumbing lines (go PEX, forget about the PVC).

Marshall Downs · Answer

It depends on the situation. There are certainly plenty of homes on slabs out there with MEP's all below ground. Though I agree I always prefer a basement/crawlspace myself.

I would double, no triple check that it is actually a crawlspace that was filled and not some other setup. If it is a crawl you could price out removing the floor and fill material then rebuilding and compare that against doing repairs, but having the systems partially inaccessible then make your decision from there

Marshall Downs · Answer

@Frank Zondlo I am guessing you have galvanized pipes instead of corrugated? My suggestion is to have the plumber mark the path for the water/drain lines and have a concrete cutting company open up the floor for you. I pay about $300-$750 for something line that depending on overall square footage. Then you just backfill and pour. Sounds like an ordeal, but with good subs it's not too time consuming or expensive.

You should also be certain to have other trades see if their work is down there as well so it doesn't get hacked up in the process.

Frank Z. · Answer

I love this idea! I think that's what I'm going to do. Thanks!

Frank Z. · Answer

Thanks for all the replies so far. I didn't think to mention this before but all the walls in the house are plastered.

@Wes Harding If only! there's two toilets. But they're both very close to the sewage line. Also, the walls are plastered, but maybe it makes sense to run the water lines through the ceiling to get into the space and then just have the sewage go through the concrete slab?

@Marshall Downs I think you've perfectly identified a key problem. I don't know if in that section of the house there was ever a crawlspace actually. Everyone from the inspector to the contractors have been calling it that but that side of the house has less room underneath than the other parts with the crawlspace. Maybe it could be a shorter crawlspace? I could probably fit but it'd be a bit tight. The exterior walls are all concrete block. Do you think it would make sense to make a tight crawlspace? You mentioned triple checking, and I'm very new to this, what should I be looking for / worried about?

@Jd Martin Thanks for the advice! I'll be sure to use PEX. It sounds like a better product.

Frank Z. · Answer

Yeah that's what I meant to say, galvanized not corrugated. Thanks @Marshall Downs.

I'm worried if I backfill and pour after changing the pipes I won't have access if something goes wrong down there. Right now it's not too big a deal as I haven't laid down the floor, but after that, yikes - sounds expensive to get back down there for repair. I was hoping there might be a better option?

Half crawlspace half concrete slab?? Any advice?

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