Small roof, disproportionate trouble
A dormer top is one of the smallest flat roofs on a house and one of the most common sources of a leak. It sits high up where nobody looks at it, it collects whatever the main roof sheds towards it, and it meets tiles on two or three sides, which means several junctions in a very small area.
This one had reached the stage where the felt was visibly aged and worn. Felt has a finite life, typically ten to twenty years depending on the grade, and once it becomes brittle it splits rather than flexes.
Why the deck comes off too
The covering is only half the roof. Underneath it sits the deck, and if water has been getting through, that deck has been getting wet.
Laying a new membrane over soft or saturated boards puts a long-life covering on a short-life base. The new covering then fails early for a reason that has nothing to do with the covering. So the old felt came off and new 18mm OSB decking went down across the whole dormer top.
Why EPDM
EPDM rubber is a single sheet. On a roof this size the membrane goes down in one piece, which means no joins across the middle of the roof at all. Joins are where flat roofs leak.
It stays flexible rather than going brittle with age, which matters on a dormer where the timber beneath moves with temperature. Properly installed, EPDM typically lasts in the region of thirty years against ten to twenty for traditional felt.
The work is covered by a 10-year guarantee.
If your dormer is leaking
Dormers tend to announce themselves through a bedroom ceiling rather than through anything visible outside. If you have staining on an upstairs ceiling near a dormer, or around where it meets the main roof, the covering or the junction detail is the usual cause.
Our guide on why a roof leaks explains how to narrow it down, including why the stain inside is rarely directly beneath the fault.
We carry out flat roof repairs and replacement, alongside all other roofing work, across Sunderland and the North East.
