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Question DetailsAsked on 6/20/2016

I want to add a third bedroom under my hillside home. Where do I start???

The crawl space is above my head and slopes, so I will have to remove a good portion of dirt, rock, and soil. Do I need to get an architect to help me out? How do I know if it is even possible to do??

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1 Answer


You of course need an Architect for the plans you will need to get a building permit, and for the contractors to bid to and the successful bidder to build to. You also need a geotechnical engineer and a structural engineer to evaluate the foundation conditions and determine what support may be needed for the hillside (because you are removing part of its support), and to design the structure to properly support the house.

Therefore, your Search the List category is Architect, but you need one with in-house or affiliated geotechnical and structural engineers that will work for and with the architect to give you a coherent design.

This is not likely to be cheap because most likely you have a stepped foundation - the front part may be 6-7 feet deep, but at the back the footings may stairstep up the slope and only be a few feet deep at the back - meaning you will be needing to add foundation height under the existing foundation, which normally involves jacking the house up off the foundation a touch while digging out and pouring the new foundation sections.

If you have land and the possibility is amenable to you, discuss with the architect the possible differences between digging out a daylight basement under your house for the added room, or building an addition for the desired space - the latter might be cheaper. In some cases like yours, you can actually get an equivalent square footage addition next to the house PLUS full basement under the addition nearly or as cheaply as digging out the crawlspace, because the crawlspace work is usually highly labor intensive and slow, hence costly.

And if your crawlspace has intermediate piers or posts supporting the house, that gaenerally makes an outside addition even more economic.

Couple of other thoughts:

1) if on septic, will the added bedroom require septic system enlargement (usually code requires septic tank and leach field sizing based on number of bedrooms) - architect should be able to answer that easily, or check for a fact sheet at local building department or water quality/DEC website, as applicable for your area

2) if planning on putting a bathroom down there, will it be able to drain to sewer/septic or will it need to have a lift pump, which can be a maintenance issue some people don't want.

3) how much bedorck or big boulders do you have in the crawlspace - obviously a lot of rock will crank your excavation price up, though could also simplify the new foundation design.

Answered 4 years ago by LCD

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