Lowering Basement Floor Disaster 3

[jerseyshore]

Cheap house flipper lowers the floor of a 1910 basement to gain 7' clear and sell it as a full basement. Old brick walls, no footings, just a rubble base.

They cut out the floor slab and dropped it down about 12"-14" then sheetrocked the whole thing to hide it. Never put a slab back in, just put heavy vinyl flooring right on the dirt.

IMO underpinning is too risky even in small stages, there no existing footing and basically no dirt left around the base of the wall, just "load-bearing" 2x3's.

So that leaves a new proper bench footing. Any thoughts on a good procedure to not compromise this thing any further during construction?

Normally I slope the bottom of a bench footing, but this is cut straight down already so do I have them backfill with something or just pour a whole mess of concrete under there? You can see in the last picture the cavity that exists under some portions of the wall.

 

[jerseyshore]

You can see it better in this photo of the side wall. They had what looks like a 3" rat slab everywhere, then went down about 7-9" below that for the dig. They left about 3-6" of slab and as you can see from my first photo in the OP, used that cavity to put the studs so that they didn't lose much interior space.

So that's why I'd probably go 6" minimum up with the notch above the existing brick. That would cover the space of the old slab plus a few inches to the next course.

 

[jerseyshore]

Yes the water issues will still have to be resolved. After they underpin they can put a perimeter drain and sump pump in the corner I would think.
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Forgot to include this earlier, but it appears that those clowns did a "bench" only at the front wall and covered it with flooring. I guess because it's a utility/ laundry room they figured no one would think twice, but didn't do it everywhere because it would've been too obvious. They chose the cheaper and easier option to just sheetrock the dirt. Unreal. I couldn't sleep at night if I told someone to do this kind of work.

 

[phamENG]

It's okay. Engineers don't know anything anyway. Just a bunch a bunch of over educated know-it-alls that are way too conservative. Buildings don't fall down....

 

[jerseyshore]

Looks like I would need a roughly 30" deep footing to get my sliding FOS at 1.0. So only about 10" deeper than I was going to go anyway. That seems worth it to not have to add in additional shoring. Then once the slab is placed it will be braced. What do you think?

 

[phamENG]

I think I'd take it down to get your sliding factor of safety to 1.5 and not rely on the slab. Turning the slab into a compression element would require a much thicker slab and a lot more reinforcement.

I'm not sure if you feel a need to help this person - by the look of the houses I suspect it's not the wealthiest of neighborhoods. If you do, then I commend you on being a decent human being. If not, I at least commend you on being a savvy businessman. But I'd be careful either way. The imbecile that did this probably did other things in the house. Things that, because they are probably long gone and that LLC is a piece of paper in a landfill by now, could be blamed on you by a lawyer simply because you have a functional business and an insurance policy. So I would say now is not the time to depend on a lot of 'engineering judgement'. Now is the time for hard numbers. It meets code, or it doesn't. Factor of Safety = 1.5 either by embedment of the underpinning or by bracing against a competent, code compliant concrete compression member.

 

[jerseyshore]

A 4" slab is typical of basements for bracing the bottom of the wall, so that part I'm not overly concerned about.

You are correct about the neighborhood, this is in a low income city. Apparently it was an abandoned house, flipper probably got it off auction/foreclosure for nothing and did this shitty work to resell for over $400k. And your assessment about me is also correct, I do get sucked into helping people out, even though I do have to think about the inherited liability of working on a project like this.

I'm going to design it properly and not leave anything to judgement. Appreciate it.

 

[jerseyshore]

Would have to go down to a 5'-4" deep footing to get to 1.5 FOS. That's basically the height of the brick wall and just not realistic to excavate in a situation like this IMO.

They are going to have to shore up the whole house both vertically and horizontally at these basement walls to prevent them from blowing in (a miracle they haven't already). Then keep the horizontal bracing in place until the slab has cured. Just need that slab to brace the base of the wall/footing to keep it reasonably sized.

Homeowner is going to have to weigh that vs the cheaper option of losing that foot of space and filling it back in.

 

[dik]

anything[/b] anyway]

That's a stretch... I know the date.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[XR250]

When I do low bench footings, I use the slab as the toe for a monolithic retaining wall. How are you resisting overturning otherwise?

 

[phamENG]

Fair enough. Shoring it is, then, until the slab is in place.

dik - you're better off than me most days. I usually have to check the calendar to see...

 

[SWComposites]

Can a house mover be hired to jack up the entire house, then build a proper foundation and basement slab, then set the house back down?

 

[phamENG]

Can a house mover be hired to jack up the entire house, then build a proper foundation and basement slab, then set the house back down?

I think that would be a bit extreme in this case, though only jerseyshore can say for certain. Just because it's a brick foundation wall doesn't mean it needs to be replaced. There are hundreds of thousands of buildings sitting on them right now and we're not concerned they'll all fall apart. We've found more economical ways of building foundation walls (among other advantages), but that doesn't mean these are inherently bad - especially if you're not too worried about earthquakes. Can't see much of the brick in the pictures, but what of what we can see doesn't look bad. It's just a matter of getting it down deeper - which underpinning can do without having to pick the whole house up and sending 20cy of serviceable masonry to a landfill.

 

[SWComposites]

pham - I agree if the only objective is to shore up the existing foundation. but if a nice finished basement is desired, them maybe something else is appropriate. either way, if I was the owner I would be getting legal advice to go after the flipper for fraud, etc.

 

[phamENG]

if I was the owner I would be getting legal advice to go after the flipper for fraud, etc.

For sure. And to have their contractor's/developer's license stripped, or have them prosecuted/fined/whatever for operating without the appropriate licenses.

 

[jerseyshore]

Just spoke to the owner who said they already spoke to a lawyer.

I was just at the contractor's office who does home elevations and foundation repair, and the issue with doing that is that there is barely any space to excavate on the sides because of the neighboring houses. You'd have to do some sort of soil shoring to even be able to get the old wall out and put a new one in.

What we do in a lot of places around my house (this one is in North Jersey) is instead of going down to gain more head height is to lift the house up and add a few more courses to get more space in a basement. Not really financially worth it though for this house.

It's going to take a lot of shoring and be very expensive, but not much of a choice if they want to keep the 7 foot basement height.

 

[Aesur]

Have you considered the horizontal reaction at the base of the wall and verify that the "cantilever" bench footing is sufficient to cantilever up from the slab and support said loading while tying into the slab? I would suspect a 6" reinforced slab would be needed minimum.

Best option IMO - force the seller to take the house back, get home owners money plus damages and moving expenses and make it the sellers issue.

 

[jerseyshore]

That's my next step, to check that bench for support.

You're crazy if you think the seller is going to take back a house. Like pham said above, the previous seller is probably an LLC that disappeared and it'll take years to get money in court. This homeowner lives there with their family, they can't wait around for that. On paper those walls should've fell down a year ago. This one has to be addressed immediately.