How far from egress should I place a footer
I am planning on adding an addition, to my house that has a 9 basement. The addition is going to have a 32 crawl space. The addition will be heated by ducts running under the crawl space. The crawl space will be accessible through a hole cut in the basement wall, which should provide additional heat. The frost, in my area is 32 below grade. The current design has the wall of the addition, and therefore its footer, right next to an existing 5 deep egress well.
Ive talked to several contractors and the City Engineering department and no one but me seems to have a problem putting the footer next to a 5 hole in the ground.
Am I right in thinking the footer needs to be 32 below the bottom of the egress well, which is about where the footer for the house is located or needs to be moved 32 laterally away from the wall.
Larry, You are commended for doing things 'by the book' and going through the permit process. You are right to question others on decisions that will affect 'your' house.
IMO you can do one or two things (besides getting opinions here)
Are you sure you just want a crawl space?
Everyone I know that has a crawl space one wishes that they had more space
We actually passed on buying one house because they put a crawl spacew under the addition instead of a full cellar
Seems you can never have enough storage space
Does the egress have a basement door flush with the house?
Or a bulkhead?
I think you are right
If freezing air can get to the bottom of that area then the frost depth would be deeper
But I also know that in my case there isn't a 40" deep foundation under my basement door - walk-out
Your logic makes sense. However, doing what you're doing is commonplace and it rarely raises eyebrows. My suggestion would be to use a few inches of foamboard insulation in the bottom of the egress well covered by dirt and gravel. That'll adequately protect the soil around the footing from freeze/thaw.
Larry, your reasoning also makes sense to me. Frost can move horizontally as easy as vertically, especially assuming the clear stone backfill surrounding the egress well.
One other important factor that needs to be considered though: The footing shouldn't be bearing on soil that close to the well. This will not only put additional load on the well, but more importantly can lead to a bearing failure as the well & stone will have little support for the side load exerted by the footing/addition weight. If it were me, & it isn't, I would dig the footing down to the bottom of the egress window, for a distance of the egress well projection from the house + 3 feet. IE: If the well extends 3.5 feet from the house, the drooped footing of the addition would be at least 6.5 feet long, then would step up to the 32" depth for the remainder of the addition. I'm no engineer by any means, & I'm sure an engineer will come on here & pick apart my advice, but I've been thru these situations many times. As I recall, if you DO NOT go down to the bottom of egress level, you would need to be somewhere between 6-8 feet away from the egress well if it is engineered. That number can vary greatly though, as it involves the over excavation of the egress well for drainage stone, bearing factors of the existing soil, footing size & re-enforcement, total weight transfered to footings, etc....
Even with the footing down at five+ feet, a few inches of rigid insulation against the footing (at the egress well) is cheap insurance.:thumbup:
KC, I think the egress well is already installed, but that is definately good advice when installing the wells.
We are under UDC code yet here in WI, & there are only 3 exceptions to the 48" frost depth:
- Bedrock less than 48" deep.
- Frost protected shallow footings when designed to ASCE-32 specs.
- Window wells, which have NO depth stated for some reason!
Another factor to consider besides the frost issue is whether the soil near the house has been compacted sufficiently to support the new footing. Chances are the new footing will be on disturbed soil for at least a few feet near the house.
No builders take the time to compact the backfill when a new house is constructed. So unless the house is very very old or the soil is self consolidating you should excavate down to undisturbed earth near the house which would be the level of the existing basement footing.
I agree with Jogr. FOOTINGS [R403]
See Figure 12 and Table 4 for footing size, footing
thickness, and post attachment options and requirements.
All footings shall bear on solid ground and shall be
placed at least 12 inches below the undisturbed ground
surface or below the frost line, whichever is deeper;
bearing conditions shall be verified in the field by the
building official prior to placement of concrete. Where
the building official determines that in-place soils with
an allowable bearing capacity of less than 1,500 psf are
likely to be present at the site, the allowable bearing
capacity shall be determined by a soils investigation.
DECK FOOTINGS CLOSER THAN 5'-0" TO AN
EXISTING EXTERIOR HOUSE WALL MUST BEAR
AT THE SAME ELEVATION AS THE FOOTING OF
THE EXISTING HOUSE FOUNDATION. That from deck building in the 2006 code, page #9: http://www.awc.org/Publications/DCA/DCA6/DCA6.pdf
Be safe, G
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