I am building a single storey extension with a lean-to / mono-pitch slate roof and have been asked by Building Control to install a cavity tray above the roof abutment.
I would like to get the roof abutment as close as possible to the underside of the window sill of a second floor window above as I am struggling to obtain a roof slope of 20 degrees or more.
My intention was to use Type E pre-formed Cavity Trays in the row of bricks immediately below the window sill and for the flashing to have a vertical upstand of around 80-85mm above the roof, giving me around 2 courses of bricks between the roof abutment and the window sill, but was wondering if it is necessary to have cavity trays immediately below the window as surely it is not doing anything in this area as the window unit is above it.
If is is not required under the window I was hoping I could install the cavity trays either side of the window in the row of bricks level with the concrete window sill thereby allowing me to move the roof abutment up by one course of bricks, what do you think.
I would like to get the roof abutment as close as possible to the underside of the window sill of a second floor window above as I am struggling to obtain a roof slope of 20 degrees or more.
My intention was to use Type E pre-formed Cavity Trays in the row of bricks immediately below the window sill and for the flashing to have a vertical upstand of around 80-85mm above the roof, giving me around 2 courses of bricks between the roof abutment and the window sill, but was wondering if it is necessary to have cavity trays immediately below the window as surely it is not doing anything in this area as the window unit is above it.
If is is not required under the window I was hoping I could install the cavity trays either side of the window in the row of bricks level with the concrete window sill thereby allowing me to move the roof abutment up by one course of bricks, what do you think.
