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Architecture/Feasibility of Cantilevered addition

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Expert: - 10/2/2007


Question
How difficult is it to add on to a second-story room without extending the foundation?  How far out can you go, and what would this do to the cost?

This daylight rambler has a small master bedroom without bath.  A possible solution is to extend the bedroom 5 feet (x 16 feet wide), but we'd rather not extend the basement -- the basement doesn't need more space and there's precious little flat yard to spare.  Is cantilevering feasible for an addition like this?  Thanks!
-Matthew

Answer
Hi Matthew - thanks for your question!

A general "rule of thumb" for cantilevers is that the parent span (the part of the structure that's not cantilevered) should be at least three times the length of the cantilevered span.

That's "generally"; your particular situation may be different, but it's a good planning guide.

The cost of a cantilever will be much less than building a foundation; make sure you adequately insulate the cantilevered part of the floor.  If you have plumbing in the cantilever (and you're in a temperate or cold climate) you'll need to take additional measures to prevent freezing of pipes.

You could also use structural/architectural brackets to help support the extended floor - might look great, depending on the house style.

As long as the addition is architecturally appropriate, it's certainly worth considering!

Hope this helps,

Richard Taylor, AIA
www.rtastudio.com
www.rtaplans.com

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Richard Taylor, AIA

Expertise

Ask me about all aspects of house, remodeling. , and room addition design and construction. Ask me about historic homes, renovation, and restoration. Ask me about materials and techniques, and about how you can get the best value for your design and construction dollar. Ask me how you can make your home a very special place. I can't, however, answer specific structural engineering questions in this forum - that's something you'll need on-site observation for.

Experience

I own a full-service residential architectural firm, and have been designing custom homes, remodelings, and room additions across the country since 1983. Check us out at Richard Taylor Architects and RTA Plans. I have written and been published extensively on the subject of residential architecture.

Organizations
American Institute of Architects, City of Dublin Architectural Review Board, Vice Chair of City of Dublin Planning and Zoning Commission, American Planning Association, Board Member Historic Dublin Business Association, Past Editor of SPLASH (a software forum), Past Editor of Open Directory Project, Assistant Scoutmaster, Boy Scouts of America

Publications
Business First of Columbus, Suburban New Publications, About.com, Cleveland Plain Dealer, Columbus Dispatch Residential Architect Custom Home Architect Remodeling Architect

Education/Credentials
Bachelor of Environmental Design (Architecture) Miami University 1983
For more about home design, check out my blog at Sense Of Place and join the conversation on our Facebook Page.

Awards and Honors
2010 Dublin Chamber of Commerce Business Person of the Year

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