Lowering/deepening basement floor to create livable space (how much, roof, foundation)

[caravan]

Has anyone done this? I am curious because we are offering on a 2 bed/1 ba house, where the upstairs is some 1300 sq. ft (HUGE dining and living rooms, smaller bedrooms and bath) and the current unfinished basement is 600 sq. ft. There is enough headroom for me (I'm 5-2"), but for my husband (who is 5-11"), the top of his head brushes the underside of the exposed beams and pipes, which means that if we wanted to finish the room and add a bed/bath, it would accommodate midgets only. Ideally, we would like to make the basement 8 ft. high and dig out the existing crawl space to add another couple hundred square feet to the finished area.

I have seen a few examples online of people deepening their basements, either by underpinning 3 ft. sections as they go around the room, or by leaving a 45-degree angle of dirt angling down from the sidewalls (for stability) and sacrificing that much square footage on all walls in order to keep the building structurally sound. I have seen quotes anywhere from $15K to $30K for a basement of this size, based on price per linear foot. But I also see a lot of people throwing up their hands after thinking through the whole idea more, deciding that it is not worth their time or money to do this. (I suppose there is always an option of building up as well, but wouldn't that cost just as much?--I have read that this issue of digging out basements is much more common in urban areas like ours, because the properties are too small to expand in any other direction.)

Thanks for any feedback. We really would like to make this work--the rest of the house is in excellent condition, doesn't need any remodeling, and we would not have to give up any comforts (other than maybe noise) while this work was going on in the basement. If you have done it, how much did it cost? Are you glad you did it?

[JamieK]

Another option, depending on how the house is built, is actually raising the house up. A house moving company could do this. I looked into this for my old home, but it had a full basement with concrete block walls. I thought about jacking the house up, inserting another row of block, and sitting it back down.

[caravan]

Yeah, we have considered this as well, but figured it would be more expensive to do so since this house was built in 1921 and the lath-and-plaster walls will most likely not take the moving well. Do you know approximately how much it would have cost to do that?

I called up the city's department of planning yesterday, and when I asked about whether digging out basements was possible around here, they said that people did it all the time. I asked if there were any neighborhoods where they didn't allow it, due to soil quality or anything... nope, they said it happened all over the city, and the permits were easy to get. Go figure, who knew this was a done thing! I'm hearing estimates of around $20K, depending on how many linear feet are involved.

[JamieK]

I just Googled "digging out a basement", and it seems like its a common thing to do. Biggest worry would be the foundation work. Probably should get a couple of engineers opinions on everything, like a soil engineer, structural engineer, etc. And find a contractor thats done this kind of work before in your area. Of the different ways to do it, this sounds like the best. Support the house on jacks and cribbing, dig out the basement, and completely rebuild the foundation walls. Of course, this is also the most expensive, and not sure if the house would be livable during this. Good luck!

Jamie

[Barking Spider]

1. I would try to get contractors to give estimates. Then ask for referrals from past clients. Then talk to those people and find out how it went for them.

2. Could you get the house you wanted with the additional square footage for another 30K? You will probably pay that much to get your basement the way you want it. Don't forget you will need a heat source too.

[MMichelle]

I have not done this - but I've known of at least 2 homeowners that did. In both cases they were historic homes and raising the house was not an option. The basement "dig outs" did the trick - very expensive.
You will need a good eng. for the project, you may need a soils report too - AND a building contractor to do the foundation, AND a contractor to do the finish work. You will need to select your vendors very carefully. Be sure they are all correctly licensed, pull the correct permits from your local building dept. AND be sure the permits are inspected and closed correctly. REQUIRE each contractor provide proof of insurance AND list you as an additional insured on their policy. As part of the project be sure your eng. does inspections on the foundation to be sure the contractor is meeting the eng. report. Be sure to discuss this with your insurance agent before hand and after.
Your local building dept can be a wealth of info - get smart on this. Done well this project can add huge value to the home - done poorly, it can be worthless & uninhabitable. DO YOUR HOMEWORK
Best wishes.

[caravan]

Thanks to all for the advice. We had the building inspection today, and I specifically found an inspector who was also a civil engineer (because of this basement issue, which I wanted professional feedback on before moving forward). Turns out the basement had already been deepened once before, as there was already a bench around the edges of the basement... why they didn't dig down 2 more feet is a mystery to me.

So the inspector advised us that deepening was the way to go, rather than raising the house, because of all the damage to the walls, windows, and roof that would occur with the latter. The house also can't take a second story, so that's out. But the inspector saw no reason not to dig down, assuming we did all the good-sense precautions of hiring engineers all around (not him, obviously) and drawing up very careful plans, getting the necessary permits, etc. This was the main thing we wanted to hear from him--basically, we know we can handle the cost, as there are no comparable houses like this within a 30K range (we're getting a good price n this Seattle market, as it is).

I should also mention that my dad is a contractor, plumber, Jack-of-all-trades type guy, so he has access to far more
economically-efficient ways of getting this done than a couple who knew nothing about remodeling, basements, etc.
So the cost should not be as prohibitive as one might think, especially the manual labor portion--my dad has bought,
remodeled (single-handedly), and sold multiple properties in his lifetime, so we have a huge advantage in this project by having him help us.

So, we know it's going to be a pain in the ass and take a lot of work and money, but we believe we have the resources to conquer this beast of a project and get some value out of it (mostly for ourselves, as we plan to live there long-term, but also for resale value). As for heat--we're thinking a heated floor would be great in a basement, thoughts?

[stevep]

Do you have enough land to add on to your house?

[caravan]

Originally Posted by stevep

Do you have enough land to add on to your house?

Not really; previous owners have already added on a little bonus room to the 2nd bedroom, but otherwise the lot is too small to add much more to it, if anything at all. The only real options will be to dig down or to lift up--the latter not being ideal since it's 90-year old Craftsman home.

[jimwill]

We are looking at doing the same thing to gain 600 sq ft. Did you go ahead? Do you have a happy ending to your story?