A roof that leaks in a steady downpour has a hole. A roof that leaks only when the wind is behind the rain has something subtler wrong with it, and it is one of the most common calls we take along the north Norfolk coast and out on the open fen. Water arriving at forty five degrees does not obey the drainage path a roof was designed around. It goes up under laps, sideways through verges and in behind flashings. If it is happening now, ring 07437 005301: we offer 24/7 emergency call-out and we inspect free of charge.
What driving rain does that ordinary rain does not
A tiled or slated roof is not a sealed membrane. It sheds water downhill using overlaps, and it relies on gravity taking the water the way the laps expect. Wind pressure changes that. It pushes water uphill under the tail of a tile, drives it horizontally through an open verge, and lifts it behind a flashing upstand that is a little too shallow.
This is why the same roof can be perfect in an August thunderstorm and wet in a February north-easterly.
The details that usually fail
Nearly always the fault is at an edge or a junction rather than in the middle of a slope.
- Verges where the mortar has cracked out or the undercloak has gone
- Shallow lead upstands and short cover flashings at abutments
- Dormer cheeks and their soakers, especially on the weather elevation
- Ridge and hip mortar that has lost its key
- Old bitumen felt torn at the eaves so wind-driven water misses the gutter
- Cracked or missing tiles that only matter when water is pushed sideways
- Chimney back gutters that fill faster than they can drain
Exposure on the Norfolk coast and the fen edge
Properties along the coast road and on open ground with no shelter take repeated pressure from the same direction, so the same elevation ages faster than the rest of the roof. Salt-laden air also works on fixings and on any ferrous fitting left up there.
On these buildings we detail the weather elevation more heavily as a matter of course: better mechanical fixing at verges and ridges, longer laps at flashings, and dry-fix systems that do not rely on mortar staying intact in the wind.
How we track it down
Wind direction is the diagnostic tool. If you can tell us which way the wind was blowing when it came in, we can usually narrow the search to one elevation before we get up there. We then inspect from inside the loft during or straight after the weather where possible, because the water track on a rafter points back to the entry point far more reliably than looking at a dry roof on a still day.
Where the leak is intermittent and nothing obvious shows, controlled hosing of one detail at a time, working uphill, is slower but conclusive.
What the repair usually is
Rarely a whole roof. Far more often it is renewing lead at one abutment, replacing a mortar verge with a mechanically fixed dry verge, re-bedding a ridge line, or reforming a chimney back gutter with a proper code of lead. The work is targeted at the elevation that faces the weather, which keeps the cost proportionate.
Common questions
Why is my roof fine in normal rain but leaks in a storm?
Because the fault is at a lap, verge or flashing that only lets water past when wind pressure pushes it against the normal drainage direction. It is a real fault and it will get worse, but it does not mean the whole roof has failed.
Can you inspect while it is still blowing?
We can inspect internally in the loft during bad weather, which is often the most useful time to do it. Work on the roof itself waits until it is safe, and we will say so rather than putting anyone at risk.
Does a coastal property need a different specification?
The materials are the same, but the fixing and detailing on exposed elevations should be more robust: mechanical fixing rather than mortar at verges and ridges, and generous lead laps at abutments.
Will more mortar sort a leaking verge?
Repointing can buy a season, but on an exposed elevation mortar keeps cracking. A dry verge system fixed mechanically is the repair that lasts.
Is storm-driven water damage covered by insurance?
Sometimes, depending on wind speeds and your policy. We carry out inspections and reports for insurance claims, and we will document what we find either way.