Correct installation of doors in tile clad dormer

When installing the cill there should be a continuous bed of silicone underneath and where the cill meets the corners of wall. Where the frame runs up the wall, there should me a membrane that runs up to stop moisture coming through

In the event of a window or doors being fitted a timber structure ,especially a dormer ,there should be a lead welded tray at the chill level ,folded up around 40/50mm to prevent any water ingress ,then the doors or windows can be beaded and sealed against the tray ,as for the vertical reveals the main breathable felt membrane should be fitted to the face of the ply and over the doors at least 25mm, battened or lathed and finished with tiles or whatever . The problem here is that the installers have cut the membrane back to far and not protected the timber ,then just filled the vertical gap with silicone ,which will never ever stop damp penetration ,my family are in the construction business over 30years ,and I have came across this issue many many times ,it’s just not taking care and rushing the job ,as they know the damp will not show for a period of time ,well after they have been paid ,hope this helps and that you get a good experienced person to sort it ,easy fix .

Hi the upvc doors should also have an expanding foam around the frame to seal. And also an external plate to cover the void with plastic on top then silicone seal. Also some sort of drip formed on the top. Could also be lack of ventilation!