I have been on a new house hunt for a while. It's been a difficult one (especially for the wife) as I have been very stubborn about wanting a dedicated room with at least 8-9 foot ceilings. Preferably 9'.
Well we found a house we both love and are making an offer on it. However the basement ceiling are only 7.8'. It is a fairly large basement. Overall around 28' by 27'. There are two support poles in the middle separating the room. My idea is to split the room at the poles (with a wall for the theater).
So is it feasible to break out the concrete on just the section of room that will be the theater and dig 6" to 1'? And repour concrete?
Who is the guy (What is the link to) who not only dug out and built his whole theater underground, but the built a garage (full of sports cars) on top of it, and at the same time made a hydraulic secret door / hallway as an entrance? I think it was in Utah or Colorado.
For this project (my project), I lowered a 10'x10' area by 1'. The costs in Toronto (including structural engineering plans and internal waterproofing for the room at the same time) were about $10K, give or take. Just the labor for the lowering was about $7K.
Keep in mind I didn't actually underpin, I used a 16" bench (which is more like 8-10" after the walls were finished). Underpinning would be substantially more expensive if you were lowering up to a foundation wall. Depending on how close to the support poles you want to lower they may need to be underpinned, although I suspect the incremental cost for that would not be too bad.
mcallister, the difficulty and thus cost depends on how deep and close to the existing walls you want to get. I completely dug out a basement in an existing crawl space for my theater (saga of the old vic). Pics in the first couple of posts. It was tricky, not just because of the amount of material removed, but because I didn't want the room to be any narrower than the existing concrete foundation. We thus had to dig out and cut off the concrete footings and then under pin the existing foundation whilst a new wall was poured. The result is great but this initial dig was a big undertaking and about the cost of adding a similar sized extension.
What's above that area? In my house, I took the ground floor and basement together to create a quasi-two story space for the theater. I ended up with the exagerated stadium effect that I was after and still have 12' ceilings.