Overlaps too small or unbonded
The membranes must overlap sufficiently and be tightly sealed. Otherwise, water runs directly into the structure at this seam.
Membranes are on: checking the second water-bearing layer
The underlay membrane is your roof's backup: it drains water that gets under the roof covering. As soon as the covering is on, you won't see anything of this layer. Leaks then only show up when water arrives in the loft.
The most common expensive defects in roof membranes
Unsealed penetrations
Antennas, ventilation pipes and chimney connections are the classic leak points if the collar is missing or merely taped over.
Damage from foot traffic and battens
Tears and holes occur when working on the roof and are easily overlooked because they are small.
Wrong connection at roof edges (eaves, verge)
A faulty edge connection can direct water behind the eaves and into the timber structure.
What you should document and check now on roof membranes
Photograph the entire roof surface
Capture both roof faces so that the run of the membranes is recognisable.
Photograph overlaps and seams
Check overlaps for unsealed spots. Take close-ups of the seams so that the bonding is clearly visible.
Photograph all penetrations individually
Record every pipe, chimney connection and bracket together with its seal.
Document roof edges and internal corners
Photograph all roof edges all the way around, plus the valleys (internal corners) and the connection to the gutter.
Note exposure time and report damage
Record how long the membrane has been exposed – prolonged sunlight makes it brittle. Report tears immediately.
Before the roof covering goes on
Upload your photos and have overlaps, penetrations and edges checked for typical weak points.