[mikereno1]

We are looking to expand our basement and had a few questions on whether this is possible.

We currently have a finished portion and then access and crawl space to another 1000 sqft that I would like to dig out and finish. The part of the house just has normal footings and stem wall up to a foot above grade or so.

The only real option I can think of to get all the dirt out is by hand, bucket by bucket unless i tore up the driveway that runs down the side of the house and dug a ramp down and could fit a small excavator in there.

How would I support the footings with more concrete? Is there a way to dig under them and build forms just for the inside part so I dont have to back fill from the outside? ie use the existing dirt as the outside form?

Any help/tips appreciated

 

[joed]

It's called under pinning. It needs to be engineered. The basic principle is you do it in thirds. For example you dig out two feet, skip four feet, dig another two feet, skip for feet, etc. Then you dig the next two feet sections.

It does need to be engineered. Sometimes even that is not enough.

http://toronto.ctvnews.ca/more/loca...htmare-little-italy-house-collapses-1.1780554

 

[paredown]

I'm thinking about doing a crawlspace to basement conversion. I found this video helpful--this is a floor lowering but the principals are the same as Joed descibed:

 

[Mingledtrash]

This reminds me of Millionaire Basement Wars. they have some serious digging.

 

[jomama45]

IMPO, underpinning an existing crawlspace is probably the hardest, most expensive way to gain low value square footage. I'd consider adding a first, or even second floor, addition first. It may sound simple and easy, but until you've done it, you'll never understand how much work it is. 1000 sq. feet is huge to underpin by hand.......

 

[mikereno1]

How expensive is underpinning? This is really the only option I have to add space with my lot and house setup

 

[Daniel Holzman]

If you want a price, bid the job out to a few contractors. No one on an internet chat forum can give you a realistic answer. I am with Jomama on this one, underpinning is difficult, often dangerous work, requires special skills and safety precautions, all of which contributes to the high cost. And a very dangerous DIY project due to the potential for foundation collapse if not properly exectured.

 

[mikereno1]

I'll get some bids for sure, just have no clue what ballpark this will be. Definitely wont be doing myself

 

[mikereno1]

So got 2 bids for this process. The only ones I could find would do it with helical piers to stabilize everything, then dig all out, add new concrete walls, backfill and put in new slab floor. $150k without finish work. This would entail destroying the landscape near the house to put the piers in and backfill, which basically ended the idea for the Mrs.

I still think it would be cheaper to do 1/3 at a time without the piers and landscape damage. More risky though

Now looking into adding a second story with bedrooms and a bath. Probably similar in cost and will be worth more resale and better living space than a basement.

 

[Fix'n it]

you could dig it out, but not all the way to the foundation, say, 3' away. then build room/s there. no touching the foundation. but, not all of the space that is there would be used.

are these called "Michigan basements "?

 

[Bret86844]

I have to ask, would it not be easier/cheaper to move?

 

[mikereno1]

I have to ask, would it not be easier/cheaper to move?

Yes, but we love the neighborhood and have a large lot that is impossible to find in our part of town. Going to make it work here

 

[Aggie67]

I remember getting quotes to put a second floor on my first house, and a bump out addition. Contractor told me he could tear my house down and build whatever I wanted, for cheaper than doing what I was asking. I ended up moving about 2 miles away.

 

[MI-Roger]

So got 2 bids for this process. The only ones I could find would do it with helical piers to stabilize everything, then dig all out, add new concrete walls, backfill and put in new slab floor. $150k without finish work. This would entail destroying the landscape near the house to put the piers in and backfill, which basically ended the idea for the Mrs.

I am surprised the pier installer said he had to destroy all foundation plantings to install the piers. We had 5 piers installed beneath our front porch and garage wall foundation in February to stabilize the house form further settlement (clay soils).

The contractor needed to excavate a 2x2 hole for each pier, and we had to move one bush before he started, but all other plantings stayed and no damage (other than to a strip of Crown Vetch which is almost a weed anyways).

The landscape damage might be to excavate beneath your existing crawl space walls, but he should be able to start in a lightly planted area and do the rest from beneath the house.

 

[ront02769]

Simple approach since it clearly does not meet your needs, sell it and buy something closer to what you want. You have something that clearly is far from what you want, tossing money on top of money to get it close to what you are looking for...and you will end compromising in the end. Ron