How we approach a leak
Roof leaks are often straightforward, but many are not. Water can travel some distance from where it enters before it becomes visible inside, and the place where a stain appears is rarely the place where water is getting in. Our investigation is methodical: we look at the evidence — moisture staining, damage patterns, the history of the leak — and trace likely entry routes rather than assuming the obvious.
We do not guarantee that every leak can be conclusively identified. Some are intermittent and some follow hidden paths. What we do guarantee is a thorough, honest investigation and a report that says what the evidence supports — including, where relevant, that the source could not be confirmed.
Common leak sources we look for
- Flashings at chimneys, abutments and junctions where leadwork has lifted, split or been poorly dressed.
- Valley gutters and parapet gutters where falls are inadequate or lining has failed.
- Flat roofs and extensions — failed membranes, defective upstands, ponding and poor detailing.
- Chimney areas — failed flaunching, pointing or flashing.
- Junctions between roof coverings and walls, dormers or rooflights.
- Gutters and downpipes where overflow or leakage allows water behind coverings.
Intermittent and difficult leaks
Leaks that only appear in heavy rain, in wind from a particular direction, or after a long dry spell are common in London. We look for the conditions that cause them: wind-driven rain at junctions, thermal movement opening gaps, and defects that only manifest under specific circumstances. We rely on visible evidence and moisture staining, so an active leak during the visit is not required.
Thermal imaging and other tools
Thermal imaging can be useful in certain circumstances — for example detecting damp patterns or moisture differences in flat roofs and roof decks. It is one tool among several and is not a definitive answer. Where we use it, we explain what it does and does not show, and we do not present it as proof where the evidence is not clear.
Leaks that keep coming back
A frequent reason clients contact us is a leak that has been "repaired" several times and keeps returning. Repeated repairs often address the visible symptom rather than the entry route. We step back and assess the area as a whole to identify whether the previous work targeted the wrong location, and the report sets out the likely cause and what would need to be addressed.
Honesty about limitations
We will not claim to have found a leak we cannot confirm. If the evidence is inconclusive, the report says so and suggests the next investigative step. For an assessment of overall roof condition rather than a specific leak, see our roof condition survey page.