Expert: Richard Taylor, AIA - 3/8/2008

Question
I am planning to build a sunroom on the rear of my existing house.  The sunroom will be built as slab on grade.  Three new walls will be framed projecting from the rear of the existing house.  It will be 16 long by 13 feet wide.  The walls will be 11 feet high with the roof peak extending an additional 3 feet.

When I approached my county code enforcement department about obtaining a permit -- as a preliminary informational request -- the building engineer indicated that to prevent racking of the walls from wind shear, I would (1) either need to keep windows and doors four feet from the wall corners or (2) if windows were to be within 4 feet of the corners I take some other steps to prevent racking.  He would not elaborate on #2 other than to say that there are "proprietary system" to achieve that goal.

Since you indicate that you do not address specific structural engineering questions, theoretically, what measures are normally taken to prevent racking from wind shear in sunrooms.  We see plenty of existing structures that are designed similar to our wants.  Would it be as simple as collar ties at the ceiling level?

Any help you can provide would be appreciated.  Thanks, John.

Answer
John - thanks for your question!

There are two easy solutions, and both are available from a company called Simpson Strong-Tie (www.strongtie.com).

The first is a system using Simpson products that they call a "braced wall".  It allows you to get the corners down to 16" wide.  Search for "braced wall" on the Simpson site to learn about it.

The second is the use of Simpson anchors at the top and bottom of all of your posts.  You cast the post base anchors into the slab and attach the posts to them; then you put the post caps at the top of each post and connect a continuous header across the  top of all the posts.  The continuous header is important - you can't just use separate headers.  This creates a completely braced frame - kind of like a timber frame building.

The Simpson site lists all products by use so the proper anchors are easy to find.

Will your code dude accept the Simpson designs? Probably, but you may still have to get a design pro involved.  Before you do that, check with your lumberyard that sells Simpson to see if their rep can get your sunroom engineered for free by Simpson - if the room's "all Simpson" they just might do it for you!

Hope this helps,

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