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Lowering Basement Floor Disaster
3

Lowering Basement Floor Disaster

Lowering Basement Floor Disaster

(OP)
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.




RE: Lowering Basement Floor Disaster

A big backhoe should level it quite easily.

RE: Lowering Basement Floor Disaster

just wow. astounding.

I think that first you have to figure out what final depth of basement you're shooting for. I presume you're working for or with the new owner and you may need to develop a few options to determine a price range. On one end of the price range is filling the basement back in with crushed stone and a new slab back to the 6' ceiling height just to undo this abomination. The other end of the range is doing whatever it takes to result in a legit living space. That would be a pretty involved shoring and underpinning operation. Not easy, but nonetheless possible, I'd expect.

For that option:
1) shore the framing. basement to first, first to second, etc. leave space to work on the interior around the edges;
2) pick a spot and begin with underpinned foundations, excavating from the outside, too. If this goes well, you get to a point where the whole foundation wall has the support of, say, 3x3 footings spaced at 9' around the perimeter, each with a wall segment under the existing.
3) continue underpinning to develop continuous support under the wall;
4) new slab.
5) new owner sues the zero asset LLC that the flipper used to buy this property.

It would be easy to imagine that the new owner would never be able to claw back the money to do this right and could decide to fill the basement and lose the 'habitable' space.

RE: Lowering Basement Floor Disaster

(OP)
I think the homeowner wants to keep the 7' basement height, but I will tell her she can get a price to fill it in too.

Do you think underpinning is worth the risk though? 100+ year old brick wall with no footing, can't excavate from the outside since this is a city with row homes. There's not much to rely on if you dig under the wall.

I think the easiest and cheapest way to keep this current height would be to build a new bench footing on the inside. Then wouldn't have to dig under those old walls. Just trying to figure out what shape/size. Also, might want to do that in stages like a traditional underpinning job just so that the wall isn't compromised further.

RE: Lowering Basement Floor Disaster

How close is the wall next door?

Anything you do could create issues there?

Short props every foot would be a good start.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Lowering Basement Floor Disaster

Bench footing...interesting. I've designed them before, but didn't know they had a name.

Perhaps 3 options:

Best/Most Expensive: Underpin the existing walls and maintain full living space. It's certainly possible. If you can get the attention of PEinc, he'll be able to help you out. Check out their website...if anyone here has the credibility to talk about underpinning, it's him. But yes, underpinning of historic structures with rubble stone walls and unreinforced brick masonry can be done. They're not exactly easy, but they are possible.

Medium Option: Bench footing. Lose some interior space, but less invasive as full underpinning and less expensive.

Worst/Cheapest option: back fill the basement to the original depth.

RE: Lowering Basement Floor Disaster

(OP)
Just a few feet on each side. Check out the street view from June 2022. Red sticker on the door. Was sold a month later, last July.

All of these houses are probably built around the same time with crappy brick basement walls. Too close to do anything from the outside.

pham, those 3 in that order were exactly what I was thinking. And funny you said that about bench footing, I had the same thoughts originally when someone told me those have a name; never knew until recently.



RE: Lowering Basement Floor Disaster

But a lot better than literally the wall next door.

Should mean you can underpin from the inside though. Assuming the property line is mid way between the houses. A cross section sketch of your thoughts would be useful to avoid misunderstandings.

What about the floor?

Water table high enough not to need some sort of water sealing?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Lowering Basement Floor Disaster

(OP)
So this was noticed because the new homeowner was getting a lot of water in her basement every time it rained. She called a waterproofing company and as soon as they cut a couple of holes in the sheetrock they said WTF we can't do anything you need to get someone out here.

I don't think water table is an issue here, but water intrusion definitely is. Obviously the wall just stops right now and the water probably pours down under the wall into the basement. Hopefully the new footing will help seal some of that up and she can figure out what the best waterproofing approach is once we have a structural design.

I'll send what I have sketched so far in a minute.

RE: Lowering Basement Floor Disaster

(OP)
This is what I had sketched up so far after discussing with the contractor. The homeowner is okay with losing some space for a less expensive repair. Of course they would like to keep that 7' clear height so that's why a bench footing seems like the best option here.

But I do feel like this needs to be performed in a stage-like procedure, just because of current condition. Those studs are retaining soil so I don't think I'd want them to remove the whole thing at once. Maybe 8-10ft lengths.

Thoughts?

RE: Lowering Basement Floor Disaster

Where are those 2 x 3 studs in this?

If this was being done before the floor had been lowered then I can see it, but now you need to do something about the missing foundation under the wall surely. The existing foundation, such as it is, under the bricks has been severely compromised and now needs reinforcement.

Can't see why you can't underpin in sections at a time, say 3 ft with some sacrificial support legs

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Lowering Basement Floor Disaster

You have to tie that little triangular 'blob' into the wall to restrain it at the top. The bottom of the wall may move. IMHO, not a good fix. You should be looking at 'real' underpinning, else re-do the wall. It's an expensive fix.

In my experience, bench footings generally go underneath the existing wall, and are part of underpinning. You really need a geotekkie for this type of problem.

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

-Dik

RE: Lowering Basement Floor Disaster

If the bench and the slab are going in as separate pours, I'd give the bench a bit of a toe, and provide a construction joint detail showing crossing bars if you're going to do it in segments.

I wonder if it would be better, since it looks to be a small house and basement, to do a system of excavation shores a foot up from the existing footing and at or just below grade level to brace the walls against each other, strip everything out, and then pour the whole bench and slab together. Not easy to maneuver around, but most good contractors with experience in this kind of work are able to work around that kind of thing.

RE: Lowering Basement Floor Disaster

(OP)
Sorry, that detail was pulled from an old job, that I just modified briefly this morning. The 2x's are just right up against the wall currently. You're right that this detail was used in the correct procedure.

Maybe I do a combo of both. Underpinning with a bench-like notch in front to secure the base of those old bricks.

Shore existing walls. Excavate dirt & remove bits of old slab. Pour down about 1'-4" of concrete for underpinning with a notch in front. Do this in a 3-stage approach x 3 ft long sections. Pour floor slab when finished.

What about shoring to prevent against sliding until the new slab is in? Horizontal across the basement short way (16 ft) from wall to wall? Right now they are lucky the soil is pretty stiff, but as all of this is removed in sections I don't want a sliding failure.

RE: Lowering Basement Floor Disaster

dik - that depends. In a small enough basement, the bench can act as a beam, resisting the thrust of the wall and delivering it to the perpendicular benches at each end, which in turn react against the bench on the far side. You can also tie it into the slab and dump the moment there, though the slab gets a lot more expensive.

RE: Lowering Basement Floor Disaster

(OP)
For the record, I dislike bench footings, probably only did it once before. Underpinning is always my first choice where possible. This is just a tricky one because it's already dug out, it's a 100+ yr old brick wall, & there's no footing to underpin against.

RE: Lowering Basement Floor Disaster

(OP)
FYI this house is a 35' x 16' rectangle.

RE: Lowering Basement Floor Disaster

Well if you can get them to do underpinning, great. Your detail looks good, but I'd take the underpinning down far enough that it doesn't need the slab to resist any loads. Can you tell where the original basement floor was? Putting the 'mini-bench' up to that level would be a good idea to keep the stresses from retaining in their historic range.

3ft should work. If the wall's in good shape you could probably go to 4ft, but this isn't the place to get greedy.

RE: Lowering Basement Floor Disaster

Those fixes don't address the water permeation issue. If you are going to the trouble of pouring a slab, probably should include some drainage features and a sump and pump?

RE: Lowering Basement Floor Disaster

pham

I've used benching as well as flush with the wall underpinning for numerous foundations... depends on the loading... only once for brick, mostly for field stone foundation walls. The benching is part of the underpinning.

16' span with maximum soil pressure... I wouldn't hang my hat on it.

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

-Dik

RE: Lowering Basement Floor Disaster

(OP)
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.

RE: Lowering Basement Floor Disaster

(OP)
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.
---------------
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.


RE: Lowering Basement Floor Disaster

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....

RE: Lowering Basement Floor Disaster

(OP)
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?

RE: Lowering Basement Floor Disaster

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.

RE: Lowering Basement Floor Disaster

(OP)
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.

RE: Lowering Basement Floor Disaster

(OP)
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.

RE: Lowering Basement Floor Disaster

Quote (Engineers don't know anything 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

RE: Lowering Basement Floor Disaster

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

RE: Lowering Basement Floor Disaster

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...

RE: Lowering Basement Floor Disaster

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?

RE: Lowering Basement Floor Disaster

Quote (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?

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.

RE: Lowering Basement Floor Disaster

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.

RE: Lowering Basement Floor Disaster

Quote (SWComposites)

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.

RE: Lowering Basement Floor Disaster

(OP)
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.

RE: Lowering Basement Floor Disaster

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.

RE: Lowering Basement Floor Disaster

(OP)
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.

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