Sagging roof span (beam)

[toppschem]

We're building a roof over my patio on the backside of my house. The roof is 12x24'. The contructor used (2) 2 x 10 x 12 nailed together as the span from the house to a post (6x6). The 2x10 was notched 4" so that the trusses will fit to the space (between 2 windows). There are nine scissor trusses installed. After we put the roof shingles, I noticed the beams are sagging so slightly. The beam is not level on either side. Question: Can we reinforce the beams by nailing another 2x6 beam to the current 2x10 and hang it to the post and blocks of the house? Will this fix the sagging and weight of northeast PA snow? What else can we do without putting another post in the middle of the span? Thx.

[Don_P]

There's not enough information for me to tell exactly what's going on, it does sound like a recipe for collapse right now. I would imagine it's going to take something other than just sawn lumber to do what you need to do. A notch is not allowed in the center third of the beam nor can it be deeper than 1/4 the depth in the outer thirds. The beam needs to be adequately supported from underneath, it really should not be hanging on a block wall. I'd suggest getting an engineer out to take a look and propose a fix, this sounds very unsafe.

[Don_P]

Thinking today, the trusses are bearing on 12' beams and half of the 24' width is supported on the 12' beam under each end. So each beam is supporting an area 12'x12' plus whatever overhang there is. So a minimum of 144 square feet. A good bit of PA is 35 pounds per square foot snow load and the weight of the roof itself is typically assumed to be 10 psf so 45 psf X 144 sf = 6480 lbs when supporting a full load of snow. Thats 4- 2x10's minimum, unnotched. I think you're into steel I beam territory if you need to do that in 6" depth.