The best way to.
Flat roof leaking at flashing.
This video demonstrates where flashing could be leaking from on a brick wall.
The other issue is if the installer nailed the shingles through the flashing then those nails could start rusting and cause a skylight to leak.
Flashing on a wall above a flat roof.
The minimum standard is 50mm.
This flashing rests on the front edge of the lowest batten with a squash fold to direct any possible.
Metal flashing copper bend at a 90 degree angle making the transition between the roof and chimney.
Over time this continued expansion and contraction can cause the flashing to pull away from the edges and corners of your roof leading to leaks and moisture that can get trapped inside your roof.
If you can aim for 150mm.
On a shingle roof the flashing will get clogged with debris and in turn the water will get diverted under the shingles where it could start leaking.
Metal flashing that runs alongside a wall loosens up or the caulking gives and a major leak starts.
Just make sure you leave enough room for gutter maintenance.
Install a gutter flashing between the gutter and the roof sheeting.
Flashing is the number one cause of leaks on flat roofs.