Skylight Problems 3

[Lion06]

I have a situation where a skylight is being installed on a 35 degree pitched roof. It's a VERY large skylight, and the load along the slope is fairly significant. I can use steel to frame it out, but the skylight sits on a curb 9" above finished roof, and I have to keep steel below finished roof for thermal reasons.

The HSS would sit on top of existing trusses and be skewed such that it's longitudinal axis is twisted 35 degrees (i.e. the top face matches the slope of the skylight).

I'm concerned about the following: If I keep top of HSS below finished roof, and build up a curb on top of it (approximately 9" high), how is that load going to get into the HSS? It's not a very wide HSS, and the wood plates put on top would want to twist off. The small moment arm wouldn't prevent that.

I know I can't be the first person to deal with a skylight issue like this. What have others done?

 

[BAretired]

Is the curb on the existing skylights vertical or perpendicular to the roof?



BA

 

[ToadJones]

I have been called to a job very recently that had two horizontal rows of skylights (4 in each) row about 8" apart in all directions. The roof pitch was steep too...12:12.
The amount of leaking around the skylights was staggering. The bead-board ceiling, rafters, insulation and even the load bearing wall were all completely soaked and rotten and after only about 5 years.
Upon inspecting the flashing (something I have done myself hundreds of times) it appeared to be done properly, for the most part. The culmination of just several small mistakes on several skylights has resulted in tremendous damage of what is a very expensive home.