Attaching Shed Roof to house

[tom855]

I'm planning on putting a screen in porch with a shed roof on the back of our house.  Plan is for a 4/12 pitch.   Because of the layout of the house, I would like to attach the back of the roof to the house several feet above the second story floor.  My question is very simple.  Are you allowed to attach the board to which the rafters attach onto the second story wall 2x4s or must that board attach to the joist board for the second story floor?  I cannot do the latter.  Thanks!

[glenn-k]

Hi Tom.  It is quite common to attach a ledger to the studs through the sheathing with lag bolts and washers.  Nails will pull away much more easily.  It is best to pre-drill with a bit that is snug on the inner diameter of the lag-- 1/2 inch lag would use about a 5/16 or 3/8 bit off the top of my head- keeps from splitting the wood.  More depth = more holding power - I'd try to go at least 3 inches into the stud.  This is what I'd do -maybe it will work for you.

I think I recall John mentioning that 1/2 inch lags were good for 450 lbs of load each -stress on the wood-  you may need the help of a local professional if codes are an issue.  He could calculate loads for your permit if necessary.  Otherwise - 1/2 the load is usually supported on the ledger and the rest on the outer support members.  Area of roof x dead load (material weight allowance) and live load (usually snow) / 2 /number of lags gives you the weight per lag.  I don't know about allowances for pitch - I just keep enough in my head for rule of thumb stuff.  This could be made self supporting also by adding posts and beams next to the wall then tying them together with lags although the ledger is most common on lighter loads.