adding a basement to a built house?

[bill mcdonald]

I am in CA, and don't know anything about basements. But I wish I had one.

 

[Der Bugmeister]

That's actually a fairly popular method of adding square footage to some of the older houses around here. When the house is on a smaller lot, and expanding outwards isn't an option, many people go down.

The typical method is to lift the house, just like a house mover does in preparation. The basement is then excavated, foundation poured and walls framed, before the house is lowered back onto the new structure. I have no idea what the cost is like, but I do know some people have gone that route because it was cheaper than going out or up.

I knew one person who did that to his older house a few years back, and they actually lived in the house during the renovation.

 

[RAMBIN]

I am in CA, and dont know anything about basements. But I wish I had one.

I know this is a bit out there for a question, but it has my interest.

I was wishing I had a basement so i had more shop space.
Installing one under a built house would obviously be be next to impossible. (Im sure someone for a ton of $$$ could do it)

I have a standard 2 car garage with cement floor and 2x4 walls bolted into the cement slab.

Could the cement floor be cut out as to not effect the house foundation, and a basement added under the garage?

This way the bottom could be shop space, and the top could fit the 2 cars as it stands now?

Is there any construction forums out there similar to this garage forum?

older houses are jacked up and basements put under them all the time....cost wise it would depend on your geographic location(digging) size of house and all that stuff but im thinking in the area of 10 big ones as a ball park figure...as far as a basement in your garage i would just forget about that the costs would be right out to lunch... the walls would have to be jacked up...the slab jackhammered and removed a hole dug a footing dug at depth, concrete walls poured then more then likely several steel beams put accross to take the weight of a new garage floor...unless u just one the lottery forget it!!

 

[Charles (in GA)]

When I was growing up in the '60 we lived in a subdivision and our house was on a cross street where we could sit out on our deck and see down hill thru the backyards of the houses on two streets. On of these enterprising owners, whose house was on a crawl space, began digging out a basement, starting at the crawlspace door. He would, by hand, shovel a wheel barrow full and race to the rear of the backyard and dump it, back again and dig another load. My dad would sit out every evening and watch this guy, the "beaver". It took two or three years, possibly longer, I don't recall, but the basement was finally dug, walls blocked inside and everything.

More recently, a former coworker had a small house on a popular lake and decided to raise it, better view plus a basement. He set up the timbers and jacks, rigged all the plumbing so it was flexible, and would round up all the neighbors to jack up the house each weekend. He would spend the next week or two blocking it up temporarily and resetting the bottle jacks, only to do it again. Finally he got it high enough and mortared the blocks for permanent piers and foundation and poured a slab floor. They lived in the house the whole time.

Charles

 

[PAToyota]

As has been said, not un-do-able. First thing I'd check into would be what the geology is. Solid rock would likely bring an end to any possibility. Around here there are a number of houses without basements - for good reason...

 

[boiler7904]

Like everyone else said, it is possible. In addition to the soil (or rock) conditions on your site, you have to be concerned about seismic design for both the lifting and the permanent foundation. I'd start by talking to a structural engineer and the local building department. Between the two of them, they should be able to tell you if this is feasible. Depending on cost, I would try to go for 9' or more of clear headroom if possible since you plan on using it as a shop.

Another idea just came to mind. How good of shape is the garage structure itself? Unless the current garage is intertwined with the living spaces (as in directly below bedrooms), why not demo the entire garage and build what you want from scratch in a relatively small footprint? Demo has got to be cheaper than all of the **** you'd go through to lift the current garage, excavate, pour a new foundation and slabs, etc. under the existing structure. Just an idea.

 

[Inetmonkey]

Bill, I have actually done something like what you're talking about and while it was worthwhile in the end, I have to say that it was a truly painful (and expensive) experience.

Our house is over 80 years old and the foundation was in pretty poor shape when we bought it. After the '89 Loma Prieta quake, it began to sag badly, pull doors & windows out of square, and our chimney was separating from the wall getting ready to fall over. We had an existing 10'x10' cellar that we had hoped to expand for more square footage, but the cost was just out of reach. Just for the permit to do the work, we needed engineering plans & calcs for the new foundation ($$$) & soil compaction tests (more $$$). We hired a bonded house mover to lift the place up & the old foundation was removed & new forms laid. We had to use high strength concrete and rebar thoughout (even more $$$). In the end, the total pricetag was a little over $30K. To expand the cellar under most of the house, it would have been over $100K.

(Edit: Remember these prices are from 1991. Now it would likely cost 2-3x as much for the same work.)

Now, I'm not trying to talk you out of doing what you want to on your house, but although doing this sounds simple, it's a pretty ugly process. Unfortunately, my location (Silicon Valley) just naturally makes things more expensive. The same project could probably be done for about 1/3 the price elsewhere in the country, bringing the cost/ft^2 into a more reasonable range, but $1000 or more per just wasn't worth it to me.

 

[ZRX61]

In California???? I just got quoted $8K for a 25x40ft slab..

 

[Hades12]

When I was growing up in the '60 we lived in a subdivision and our house was on a cross street where we could sit out on our deck and see down hill thru the backyards of the houses on two streets. On of these enterprising owners, whose house was on a crawl space, began digging out a basement, starting at the crawlspace door. He would, by hand, shovel a wheel barrow full and race to the rear of the backyard and dump it, back again and dig another load. My dad would sit out every evening and watch this guy, the "beaver". It took two or three years, possibly longer, I don't recall, but the basement was finally dug, walls blocked inside and everything.
Charles

I know a guy that dug a 20 X 20 10 ft deep under a house, He did it to make a work out room so the pick and 5gal Bucket did the trick as he did it.

My father dug a crawl space under our place about 2 feet deep and 3 feet wide with a GI shovel and 2 two gallon buckets.

 

[russlaferrera]

We dug out our basement many many years ago. My dad and I dug a 8 feet x 4ft hole on the outside. Then dug a 4ft trench under the house, keeping 2ft from the original foundation. we did 1 wall at a time. Then we put in a footing then a wall, backfilled and started on the next wall. When we were done with the walls we finished digging out the rest. when done digging we poured the floor. This was done with a pick and shove, in 3 summers.

Today I would do it the same way except I would use a electric jackhammer instead of a pick. Then I would contract or rent a Bobcat to remove the dirt.

Also a factor... where are you going to put the dirt?...russ