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new basement in existing crawl space?

allmyfingers's picture

I am looking into the possibility of putting in a basement into an exixting house that only has a crawl space, is this do-able. The current crawl space has a dirt to bottom of the floor joist distance of about 4.5 feet. I just can't think of any way to excavate the dirt efficiently, let alone placing forms and pouring. Has anyone tried/heard of this beeing done? thanks,

(post #65779, reply #1 of 17)

I have seen it done in a commercial building.  However, the footings were designed from the beginning with that in mind.

I have heard of companies in California that are in the business of lifting a house and putting a garage in underneath.  I suspect that something similiar to that is what you are looking at - and NOT cheap.

(post #65779, reply #2 of 17)

A friend bought some land in rural Georgia that had a crumbling 1890's farmhouse on it. I'm not even sure if it had a proper foundation. He jacked the house up, poured foundation and set the house back down. Granted, it was a small 1000 sq ft structure. He wasn't interested in making the crawlspace any larger though.

The farmhouse looks pretty nice now. He built an addition to the side and built a second floor, and put loghome-type "shingle" (I guess you could say) on the outside so it looks like a loghome. When he first bought the land, I was about to suggest we light it up and drink some beer.

(post #65779, reply #3 of 17)

I lived in a house in PA that had that done. They dug out an access ramp on a gable end that later became a bulkhead. Then, they dug, probably by hand and wheelbarrow. To avoid undermining the footings, the excavation stayed about 3 ft. inside of the exisinting foundation. Once the hole was complete, they laid up a concrete block wall to the height of the original crawl, and poured a cap on that. In effect, there was a concrete shelf about 3 ft. wide all the way around the basement.

Andy Engel

Senior editor, Fine Woodworking magazine

Other people can talk about how to expand the destiny of mankind. I just want to talk about how to fix a motorcycle. I think that what I have to say has more lasting value. --Robert M. Pirsig

Andy Engel

Never try to teach a pig to sing. It wastes your time and annoys the pig.

(post #65779, reply #4 of 17)

Thanks andy, that is about what I was considering, I was just looking for some technique/technology to make the excavation and extraction of the dirt easier. Having to do it by hand would be a @#($! of a job. rick

(post #65779, reply #7 of 17)

Helped with one as a kid in the 50's and did another solo (just so I could say I finally did one) with shovel and wheelbarrow.  Took 3 months.  The shove WB advantage is that you can dig out 4-5 ft at a time to within a foot or so of the existing footing and pour the counterwall/embankment as you go, then no need to jack the whole house.

Have fun!

(post #65779, reply #17 of 17)

I'm thinking about building a bungalow on a crawlspace, just so I can dig the basement out by hand later, and say I did it.

; )

Hey, I found the saw fence. I'll go post that in the appropriate thread...

A person with no sense of humor about themselves, has no sense at all.


It's a small world. Until you have to walk home...

(post #65779, reply #10 of 17)

20-some years ago in South Carolina, a neighbor wanted his crawlspace deepend and squared up so he could pour a slab in it and have a little headroom. The contractor sent one man: a dwarf (little person?) with a short shovel and a little wheelbarrow. I'm not kidding, either.

Many's the time I wished I was a 90-pound Asian guy for crawlspace work. Being big and strong isn't always a benefit.

(post #65779, reply #13 of 17)

In effect, there was a concrete shelf about 3 ft. wide all the way around the basement.

That shelf method and slow digging seem to have been popular with the older rural crowd.  A lot of places around here have had that done.   After I had contended with a leaky crawl space  through a few bad winters I understood why they thought it was worth all that effort.

(post #65779, reply #5 of 17)

My neighbors did something like that. They hired a GC to come in and put a full basement in.

They used a dozer (sans roll cage) and skid steer to do the digging. They suported the house temporarily, and poured the foundation in sections. The project took about 8 months.

I think they spent something like $50,000 before they were done. They paid about $40,000 for the house. And I'd venture to guess the remodeled house is worth about $60,000 now.

Q: Why are Michael Jackson's pants so small?
A: Because they aren't his.

(post #65779, reply #6 of 17)

Look around for a local house mover.  They can pick the place up on long enough steel to allow you to work under it with equipment and give it a full size basement.  Get a bid, it might not be as expensive as you think. 


-- J.S.




-- J.S.


(post #65779, reply #8 of 17)

Couple years ago some people did one out in the country on an old farmhouse.  Didn't know the people but thought it was interesting (most of what they did has already been mentioned by others), and have filed it away in the back of my brain in case I ever need to make use of it.

They jacked the house up several feet.  Excavated out a ramp down to what would be the basement so that they could get a Bobcat in (and whatever else, I just saw a Bobcat).     I suspect they were redoing a basement, so would have had all the old concrete/block to remove prior to forming up the new basement.

Excavate, form up, pour the concrete, lower the house back down, connect it, reconnect utilities.

You're probably looking at a house mover to jack the house, and then a regular concrete guy to do the basement.

I believe they later turned the 'ramp' area into an exterior access door.



I was gratified to be able to answer promptly. I said, "I don't know." -- Mark Twain

Edited 4/18/2005 4:11 pm ET by JohnT8


Time is the coin of your life. It is the only coin you have, and only you can determine how it will be spent. Be careful lest you let other people spend it for you.
-- Carl Sandburg

(post #65779, reply #9 of 17)

Jacking-up is not an option and the shovel and WB isn't feasable with 130 cubic yards to move so it isn't looking do-able. Thanks for everyone's input. rick

(post #65779, reply #12 of 17)

Why isnt jacking up not an option.

It does not have to be far.

We did this for a person, Only lifted the house about 6 inches and even reconnected all the utilities.

the jacking was with steel beams that went out past the house by about 4 feet each side. then as others have mentioned it was dug out with equipment, and a full basement put under half the house ( L shape house) then with the house up  it was easy for subs to come in to ohter part and we replaced all plumbing lines, insulated the floors and replaced about half the mudsills, and retrofitted the old foundation with earthquake straps.

However , in Boss Hogs example , pputting 50k into a 40k value house to get 60k is not a good way to go

but who am I say, I blow money issues all the time

(post #65779, reply #16 of 17)

Well, noticed nobody said WELCOME yet, as puched up your profile to check on age.

Now that that is said, as to:

WB isn't feasable with 130 cubic yards to move so it isn't looking do-able

Tell us, are you over 70, disabled, or just plain lazy? <G> (Newbies gotta get somebody to razz 'em)

The digout mentioened in my post I did when in mid 50's, lost 15 # of flab, unfortunately have gained it back <G>.  Gotta admit though, the digout I did at 55 was horizontal out a daylight wall and only 124 yards ( 20 by 30 by 6ft).

(post #65779, reply #11 of 17)

This is done fairly often. Two basic ways:

1) Lift house (get house movers to do this) and possibly move it aside. Excavate and build relatively "normal" basement. (A small Bobcat can often do the excavating if soil conditions are OK, making it reasonable to do this with the house more or less in place and possibly even occupied.)

2) Dig out by hand, leaving sufficient soil adjacent to current footing to support the load. (Depends a lot on soil stability.) Build new basement wall/retaining wall in excavated hole, either poured or layed. This approach doesn't give you a full-sized basement since you must avoid undermining the original footings.

I've seen approach #1 (without moving the house) basically completed in about a week. It can go fast if you have motivated contractors. Of course, once the house is on its new foundation there is still several weeks of work needed to fix up plumbing, etc.

I've never seen approach #2 being done, but have seen several old homes where this had obviously been done in the distant past. (Also a couple where an existing basement was similarly deepened.) The basements made this way will never look "right" or be really suitable for additional living space, but it depends on what you want, I suppose.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #65779, reply #14 of 17)

I have seen it done a few different ways. One is using steel beams to support the house and digging the hole with a bobcat which allows for pouring a new foundation at the exterior walls. I have also seen a hole excavated under an existing foundation and new walls poured with ICF. ICF's light weight and no need to remove forms make it ideal for crawl spaces.

Hope this helps

Adam Greisz

Owen Roberts Group

10634 East Riverside Drive # 100

Bothell, WA 98011

Office (425) 483-0234

Fax (425) 481-0299

Cell (425) 273-6624

Wood is Good Adam Greisz<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />  

(post #65779, reply #15 of 17)

I've seen all the ideas described.

Here in VT, alot of the old houses need the old rock basement walls replaced.

The usual way is to support the house and dig it out.

I had a small mudroom supported on piers.

I took a large 6x6 beam and supported it with a jack post.

Dug it out with an mini-excavator, with a small amount of digging by hand.

Poured up new walls to it.

Of course, one half was supported by the house at the time.

I can't see why you couldn't do a whole house in halves this way.