Digging out the cellar
I would like to have the dirt floor of the cellar of my brownstone dug out to increase the ceiling height. Has anyone done this? Is there anything I should be wary of?
basementbound
in Cellar 12 years and 10 months ago
10
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10 replies
Putnamdenizen | 12 years and 10 months ago
Alas both experience and common sense are in remarkable short supply amongst many of us who are renovating our own homes. When you do something which has the possibility of destroying a neighbors home or killing someone, you should consult a professional and get a permit. I refer to the what happened on MacDonough street. If I thought my neighbor were digging out her basement without a permit, I’d call DOB.
brucef | 12 years and 10 months ago
putnam – I’ve spent too much time with engineers who are clueless. I am an engineer, and experience and common sense are more valuable than give me a check for $1,000.00 and I will recommend a useless but extremely expensive solution to a problem you don’t have.
Putnamdenizen | 12 years and 10 months ago
Digging out a basement without an engineer report and without a permit is pretty damn selfish. Given that the house can fall down, and take your neighbors house with it, I am amazed that so many (including someone who pedal himself as an competent and careful handiman on this site) are so cavalier about it. Not okay.
brucef | 12 years and 10 months ago
Neat idea Bond. A lot of work but it sounds like it “Builds Character” Down by us we strike water if we go down that deep. (27″ below slab)
Bond | 12 years and 10 months ago
A lot of variables here, but I can tell you from personal experience that many of the older stacked rubble basements in this area do not have footings. Also, depending on the age of the building, many of the foundations were originally dry stacked with no mortar. Sometimes people would go back and point after the fact, but this means that you have a wall with no support other than weight, gravity, and hopefully well laid stones on one side. I’m actually about to start a project with brick basement walls and I’m curious to see if that has footings, I’m assuming that it does, but as Bruce suggests, I’m digging a test pit to make sure. What I’ve had to do in the past is dig out three foot sections at a time, starting with the corners, dig out flush to the walls, bend #5 rebar into sort of reverse grappling hooks, drive that under the last stones in the wall, using racheting straps, support them off to the side, then excavate under the wall to the required depth, pour the footing, let that set, put a form in front and on the sides with rebar protruding so I can tie in the next sections after the face, and then pour a wall to fill the gap between the new footing and the previous wall, let that set, cut the rebar flush and move to another section. We did one corner at a time, then once the corners were done, we could do more sections, always doing a middle section. All told, it took two guys about a month just for the foundation. You’re also talking soil that’s fairly compacted, so if you dig out a one cubic foot section, you end up with two cubic feet of dirt, something else to take into consideration. Bottom line, it’s a lot of work, which translates into a lot of money for space that is never going to be all that livable.
brucef | 12 years and 10 months ago
In reviewing my comment above, I should have added a maybe to the scenario of excavating 12″ of dirt. Your mileage may vary, and you might only go down 2″ before encoountering the tops of the footer blocks sticking out. Given the thickness of the new slab and the fact that now you will level to the highest spot, We have in the past ended up with no net gain. And that’s a lot of soil to haul and a lot of cement to spread (assuming X yards of mud off a truck)
brucef | 12 years and 10 months ago
Steve is certainly on the right track. The trick to initiating this job is accepting the limitations that you might encounter. If you start out by ordering the gym equipment that will soon fit because you plan to pick up another 14″ of height, you are foolhardy. Don’t forget to deduct 4-6″ of new cement slab. Your existing slab is unlikely level, but presumably your new floor will be. So you may remove 12″ of loose pack dirt from existing floor before you come level with the footers under the foundation walls. I personally would go down 3 more inches (probably half the height of the footers), so that my new slab reinforces but grabs the footers. So you may not necessarily end up with more clearance in the cellar, and that is the risk you take. I would dig a sample hole in the low spot along the foundation, and try to figure if the whole job is worth it. It’s rough to engage a contractor at substantial expense, only to possibly end up just about where you started, but at least you would have a solid slab. The older buildings (older than Park Slope) had foundations that were substantial. The technology evolved over time, but they are based on considerable mass and rigidity, gaining their strength by being a massive unit, but not from modern deep, narrow footings. Builders didn’t have machines, they were hand digging. So don’t be surprised to have footers maybe 16″ X 6″X 20″, laid in the same dirt. Never a dull moment.
pigthree | 12 years and 10 months ago
a meteor could hit your house as well and destroy the whole thing. This is done all the time. Hire someone who does this type of work and can prove it. Permit it.
Townie | 12 years and 10 months ago
This could happen… check Brownstoner search engine for “329 MacDonough”
stevecym | 12 years and 10 months ago
I would be concerned about not going so deep as to come close to the depth of the footers. If you compromise them, you will want to add foundation below them which is a tricky and expensive task to carry out properly. also, doubtful you will encounter this in older structures, but the footers may be set in a little (wider than the actual wall), so your intended floor may be small than you plan. Any pipes you might encounter? I know if I did this in my house, I would hit the waste line pretty close to the surface at the back of the house. Steve