Roofing

Advice on Apron Flashing over a Lean to Roof

Anonymous user 03/03/2024 - 3.27 PM

Hi All, We have recently added a new rear extension 3.9m by 3 m. The roof is a pitched lean to roof with a pitch of 17 degrees . The builder has put an apron flashing where the lean to roof abuts the wall. The builder has used a code 4 lead - 25 mm tucked into the wall, 75 mm upstand from the lowest part of the tile profile, 1.5 m max length of flashings with laps of 200mm and 200mm of the apron lap over the tile. Therefore he has used 300mm Code4 lead rolls cut into 1.5 m lengths. When the building control inspector was on site - He recommended that the lap between flashing pieces and the apron lap over the tile should be 290mm based on a table from the RLSM manual for pitch dependent lap lenth. My builder continues to insist and quotes a different section of the RLSM manual and says the lap length should be 200 mm for low pitched roofs for lean to roofs. The tiles used are redland grovesbury tiles. They have a profile and the lead has been bossed to fit the profile. Also the building control recommends that the free edge of the lead be clipped . The builder has said he has used silicone instead to fix the free edge. Can you please advice on the right specifications to follow for a lean to roof. The key question being what should be the laps between flashing peices as well as overlap over the tile for the apron for a 17 degree lean to roof.