When a shed roof ties into an existing roof the new roof could be a simple lean to that covers a deck or porch or it could be the shed roof of a substantial addition.
Shed roof addition to existing roof details.
The addition can be designed as a smaller separate block with a shed roof turned perpendicular to the existing larger roof.
Work from the height of the outside of the new shed roof.
This is the simplest solution a single slope that s attached to the original house at the high point and.
Depending upon site conditions it might require altering windows at the second floor or creating an unobtrusive notch in the new roof to accommodate the existing windows.
If you re adding to the gable end of the house the side wall that goes up to the roof s peak it s.
If the outside edge is 8 feet high and the area being covered is 15 feet attach the shed roof addition at least 9 feet 3 inches above the level of the porch or other area being roofed or 10 feet 6 inches for a 2 pitch.
To do this we had to extend the plane of the shed roof out over the porch roof creating a small triangular extension of the existing roof.
There are four main roof options to consider.
The bottom of our blind valley was about 30 inches short of the bottom of the porch roof so we extended the line of the valley down to the edge of the new roof.