Ask Your Question

Angie's List Answers is the trusted spot to ask home improvement and health questions and get answers from service companies, health providers and consumers. For ratings and reviews on companies in your area, search Angie's List.

 
 
or
Submit
Top 30 Days Experts
Rank Leader Points*
1 kstreett 240
2 Guest_9020487 110
3 Guest_9190926 105
4 GoldenKid 100
5 ahowell 95
6 KnowledgeBase 95
7 skbloom 80
8 Guest_98024861 70
9 Guest_9311297 70
10 Guest_9400529 70

*Updates every 4 hours

Browse Projects By Category

Question DetailsAsked on 5/15/2013

I want to see if it's possible to expand our basement by excavating the crawl space. What type contractor should I look for?

The crawl space is under two bedroom at the west end of the house the rest of the house has a basement. I want to get some idea if it's possible to excavate the crawl space and expand the basement by doing so. The crawl space just seems like a waste of potentially useful space that could be used to expand the basement.

Do you have the same question? Follow this Question


Voted Best Answer
3
Votes

Short answer - yes it is possible. However, generally you are looking at major $, and a lot of workers tracking dirt up and down the basement stairs unless you have (or can easily add) an outside basement door.

You would need a General Contractor as well as a foundation specialist if you use a General, who will handle permits, minor electrical, plumbing, and drywall repair issues even though most of the heavy work may be done by the foundation specialist subcontractor. If you go the lift beam method, then it might be a house mover doing the lifting, then the General and normal trades handling the rest.

When a house is built with a part basement and part crawl space, the footer (the concrete strip support pad the foundation wall is bonded to with rebar and sits on) typically sits a foot or two below the basement slab. Then, to save money, they "step-up" the footer to a shallower depth for the crawl space. This means that to deepen the crawl space to full depth, you also have to deepen the foundation. It is very rare to put in full depth foundation all around, then backfill part of it to crawlspace depth - if you have gone to the trouble of full depth foundation all around, why not pour a slab and sell the additional basement footage too ? See if you can come up with the builder's plans p they will show you what the footer does.

Deepening the crawl space to full depth is commonly done in one of two ways for residential jobs (there are several more sophisticated methods such as pin piles used on large or very tricky commercial jobs, or on historic buildings with weak foundations and walls) -

1) by carefully excavating the crawl space to the new footer depth (say about 5-8 feet below ground level, depending on whether you have a daylight or full basement) bit by bit along the foundation (3-5 feet at a time, typically), usually tearing out the existing foundation for that section while temporarily support the existing wall and joists, then pouring a new concrete footer and foundation wall up to the bottom of the house beams. Occasionally, they will be able to leave the existing wall and pour the new foundation up to and connect to the bottom of it. Then you move on and do another section the same way, so you are incrementally removing dirt, building a new wall section, then moving on. This is quite expensive because of the limited work space and difficulty of getting materials in and waste dirt and old foundation materials out, and the slow progress due to having to wait for concrete to set before you can buid the wall on the footer, and before you can move on to the next section.

2) by cutting slots in the existing crawl space walls and sliding heavy steel beams through crossways under the floor joists and picking up the weight of the section of the house over the crawl space on jacks, elevating it about 1/2 inch above the existing foundation, all at one time. Then they can remove the existing crawl space foundation and all the dirt all at once, and pour a new footer and pour or lay a new foundation up to the bottom of the walls, then lower the house back onto it and pull out the support beams.

Either way, because of the restricted work space and waitingon concrete setting, the excavation and new foundation will cost about 2-4 times as much as one done outdoors. Therefore, while this type of job is done on occasion, a contractor's or architect's estimate usually shows that you can build a totally new one story extension or Florida room for not an exorbitant amount more, and that new space is worth a lot more to most homeowners, and certainly to a new buyer, than basement space.

As one example, we had two neighbors years ago who had the numbers run by an architect, and for one the estimate was only 30% more to build a large Florida room than to reclaim a crawl space about 1/3 smaller in floor area. For the other they could get the foundation and rough framing (without siding, roof, or interior) for a basement-less new addition the same size for the same price as digging out the crawl space. For this reason, when crawl space expansion is done on a residence, it is usually a do-it-yourself job (and you have to be pretty experienced to do it right).

One other factor of significance if you dig out the crawl space is all the utilities (wiring, pipes, ducts, etc) have to be checked to see that there is freedom of movement at the interface between the area over the crawl space and the rest of the house, as there is bound to be a little bit of movement between them. It is also almost inevitable that there will be minor non-structural cracking and slight separation of plaster or drywall walls and ceilings at the junction area over the first couple of years afer construction. Nailed-down hardwood flooring and vinyl near the interface can also buckle, though "floating" laminate floors are usually OK. Of course, if the contractor is incompetent or inexperienced, serious damage to the house can result, particularly if the foundation collapses while he is digging.

Therefore, I would not recommend this route except for a very expensive house (as in building a wine cellar or safe room), a historic house where additions are prohibited, or one the owners just love and intend to live in for many more decades but do not have land space for an addition. I would put the money into an addition if you need the additional space and have the land.

Answered 6 years ago by LCD




Related Questions


Terms Of Use
|
Privacy Policy