Why flat roof detail cannot be rushed
Check the deck first
A new covering needs a sound base or the same problems can return underneath it.
Keep water moving away
Falls and outlets are reviewed so rain does not sit where it should drain.
Focus on the roof edges
Perimeters, upstands and penetrations are common weak points and need careful sealing.
Flat roofs work best when water can move
A flat roof only performs properly when the structure underneath it is sound and the water has somewhere to go. Standing water, blistering, splits, lifting edges and damp below the roof are all signs that something in the build-up or detailing needs attention. We look at the condition of the deck, the falls across the roof, the outlets that drain it and the perimeter junctions around walls, parapets, rooflights and vents.
Those are the areas where flat roofs usually prove themselves or let you down.
The small details decide how long it lasts
On London flat roofs, the right system depends on roof size, detailing, intended use and how much ongoing maintenance you want. Before a new system goes down, failed layers may need removing and the deck may need checking or making good. From there, the new covering, outlets and edges need forming carefully so water runs off as it should. A tidy surface alone is not enough if the drainage and junctions have been left to chance.
Frequently asked questions
What usually causes problems on a flat roof?
Poor falls, damaged coverings, weak edge details, blocked or badly formed outlets and a failing deck can all lead to trouble. Flat roofs depend heavily on how the water is directed off the surface, so defects often start where movement, drainage or junctions have not been properly dealt with.
Do old layers need removing before a new flat roof?
Sometimes they do. If the existing layers are badly failed or hide problems in the deck beneath, removal can be the sensible route before a new system is formed. That makes it easier to inspect the structure and avoid trapping defects below the new surface.
Why are walls and rooflights important on flat roofs?
Because the junctions around walls, parapets, rooflights, vents and other penetrations are where many leaks begin. The broad field of the roof matters, but these change-of-level details are often the real test of whether the system stays weather-tight over time.