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Question DetailsAsked on 3/13/2015

What is the average per square foot cost for addition?

I'm adding a 400 square feet of living space on my second floor on existing foundation. That will include a bed room, a bathroom and a play area. I'm not looking for high end finish, but not low end neither. What is the per square foot cost range I'm looking at? I interviewed over 10 contractors and I was very surprised that the range I got is from $250 to $500/sqft. Most of them are over $300/sqft. Is that normal? I live in NY, and my current house value is about $325/sqf. Thanks!

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Looking at a couple of cost guides and 2013 home builder association info, looks like normal significant addition building cost for NYC urban areas is about $350/SF except $400-500/SF in higher-priced areas like Manhatten and up to $450-600/SF for high-end suburbs like out in CT; about $300-350 SF for Albany Syracuse and Buffalo areas, and down to $250-300/SF for many other "city" and larger town areas in NY state, and as low as around $200-300/SF for some rural areas outside city or urban zones. Of course, these are wide ranges - but sounds like, assuming you are in an urban area, your survey of 10 contractors came into that general range unless you are in a rural area. Certainly, with 10 contractors saying $250-500, I would be highly suspicious of any outside that range, and "most over $300" indicates anything below that range you need to be sure the contractor is including all the costs.

I suspect a good portion of your range might be the 15-20% of project cost for permits and fees and plans by an architect, which some might have included and some not.

Another BIG factor I just noticed is you said second floor addition - you might be tied into that by land space and zoning factors, but you are paying to remove and replace a roof and framing in that cost and a lot of protection of the house during construction while the roof is off, so I would talk to my architect if I were you about (assuming you have space) about whether a lateral addition on new foundation would be cheaper or more desireable. Might talk to your realtor too about differences in resale value - a larger footprint is commonly considered more desireable than an added floor, especially if it is built with the possibility of expanding into an in-law apartment in the future. It is not uncommon for an addition on the side of the house to cost no more SF, even with new foundation (and probably in your area full basement), than raising the roof - and of course the basement space is essentially "free" or very cheap additional space in an area like yours where you probably need a full-depth foundation to get below frost depth. In many cases, deepening a half-height basement to daylight or full-depth basement costs only $15-20/SF more, yet you get double the usable space in the deal - you might even consider that part of your 400SF of new space you want (like playroom) and reduce the 400SF footprint accordingly. Of course, each case is different, and an addition to the side does carry a higher heating/air conditioning cost than building up.

Answered 5 years ago by LCD

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