In the April/May 2000 issue of Fine Homebuilding, an article by John Spier showed the framing of a “Nantucket Dormer” on a cape cod style house. (two gable dormers seperated by a shed dormer) This front wall of this dormer was set back from the first floor wall by about a foot. Several homes in my area have had dormers added, but most have been built with the second floor wall directly on top of the first floor wall, creating one large exterior wall. I think the set back dormers, like that in the article, look a lot better.
So – here is my question; I am interested in having a similar dormer added to my 1939 cape cod, but what floor joist structure is needed in order to support the offset walls? (dormer would be home to a bathroom (no tub) and walk in closet)
Currently, the second floor of my house is framed with 2×6 floor joists that are spaced 16″ on center. The joists in the area in which I want to have the dormer built span from front to back of the house – but only have about a 9 foot of span from the exterior wall to the first load bearing wall on the inside of the first floor. The dormer wall would sit perpindicular to these floor joists.
Would the current structure of my house support this dormer? Or did all my neighbors build to the exterior wall for good reason?
Replies
Kinter, your neighbors all have their dormer walls built above the ones below because that's the way to get the most space for the least money. As you noticed, aesthetics suffer in the tradeoff.
2x6's spanning 9' are probably undersized to support a dormer roof, but it depends on the live load where you're located, how far back from the outside wall you place the dormer wall, and how wide the dormer is.
Sometimes you can add additional rafters to either side of the dormer to carry all the weight. The wider the dormer the less well this technique works. Really what you need to do is talk to a local contractor, architect, or engineer to determine what's best for your unique situation.
Funny, I live on Nantucket and can think of only 2 or 3 houses that have what's known as a "Nantucket dormer."
Edited 10/28/2004 9:43 pm ET by mike maines