I am re-doing a 20 ft by 10 ft. low slope roof on an enclosed porch that
is attached to the side brick wall of the house.
I removed the old roll roofing and plywood. The 2 x 8 inch roof joists
are 16 inches apart and run up to the brick wall from the roof edge.
The plywood was originally nailed to the joists essentially creating a
near airtight box with no ventilation.
The ends of the joists at the soffit are blocked. At the brick wall the
space between the joists is empty. There is a vapour barrier and mineral
wool insulation in the right place.
I will put down new 5/8 plywood and self-stick roll roofing.
Since there is no existing ventilation I have been trying to come up
with a strategy to get a ventilation flow from the soffit to the
higher portion of the roof.
I am considering drilling holes in the end blocking boards at the soffit
bay and holes in the top end of the joists in a line where they sit on a
"sill" like beam and vent that line of holes to the soffit at the front
I hope my description is sufficently clear.
I would appreciate any suggestions.