Caerphilly sits in a basin with high ground around it — Caerphilly Mountain to the south, Mynydd Machen and the ridges of the Rhymney Valley to the north and east. That setting does something specific to wind, and it explains a lot about the storm damage we are called to in the town.
Air does not slow down when it meets a ridge. It is forced upward, accelerates over the top and then breaks into turbulence on the far side. T & T Roofing South Wales repairs storm-damaged roofs across Caerphilly, and the pattern of that damage has more to do with turbulence than with wind speed on its own.
Below is what we are most often called to in Caerphilly, roughly in the order it comes up. If what has happened to your roof is not on the list, call anyway — it is not an exhaustive list, it is the common ground.
It is natural to imagine wind pushing a roof. In practice it pulls one. Air moving across a pitched roof accelerates over the slope, and faster-moving air exerts less pressure. The result is suction on the outside of the roof while the air inside the building remains at ordinary pressure, so the covering is being lifted from beneath as much as pushed from above.
Turbulent air makes this worse, because turbulence is not steady. It arrives as rapid changes in pressure, and a fixing that would hold against constant load can be worked loose by repeated sharp tugs. Downwind of high ground, that is exactly the kind of air a roof gets.
Why this is useful and not just theory. It explains why Caerphilly roofs often lose material from the ridge and the upper courses rather than from low down, why gusty nights do more damage than steadily windy ones, and why properties on the slopes below the ridge lines can fare worse than more open sites nearby.
The ridge is where the suction is strongest and where the covering has least protection, because there is no course above it. On a mortar-bedded ridge, decades of thermal movement have usually cracked the bond long before any storm arrives, and the ridge tile is then sitting rather than fixed.
We can assess mortar-bedded ridges, damaged dry-ridge components and the ridge sections that are still in place but no longer properly secured. That last category is the one worth finding, because it is what fails next time.
Damage tends to start at an edge or an interruption: the verge, the eaves, a chimney, a dormer, a rooflight, or the point where a lower roof meets a higher wall. Once the wind has got under one tile, the gap it leaves gives it a purchase on the next.
Where the surrounding roof is sound, the repair replaces the missing materials and re-secures the area around them. We check outward from the gap, because the tiles that have been loosened but not yet lost are invisible from the ground and are the reason repairs sometimes need doing twice.
Water follows the path of least resistance, and that path is rarely straight down. It can enter at a lifted tile near the ridge, run along the underside of the covering or across a batten, and appear through a ceiling well away from the damage.
We work from the visible symptom back towards the likely entry point, checking the junctions that driven rain reaches and the covering above them. Repairing the nearest suspicious-looking area is how a leak comes back three weeks later.
Caerphilly's housing spans Victorian terraces, substantial interwar and postwar estates and newer development, which means both slate and tile are common. On slate, the usual finding is fixings that have corroded while the slate is still sound. On tile, it is more often a loss of interlock and restraint.
Both are repairable where the surrounding roof has life in it. What we will not do is quote a patch on a roof where the same failure is about to happen across the slope, and then act surprised when it does.
A chimney stack is the most exposed part of any roof, standing clear of the slope in exactly the turbulent air described above. Storms find loose pots, cracked flaunching, open mortar joints and flashing that has lifted at the base.
Unused stacks deserve particular attention. Without the drying effect of a working flue they stay damp, and damp masonry weathers faster. A stack that has not been used in thirty years can be in considerably worse condition than its appearance suggests.
Suction is hardest on flat roofs of anything, because the whole surface is in the uplift zone and the covering is only mechanically held at its edges. Wind gets under a trim or an upstand and peels inwards from there.
We assess felt, EPDM and other flat-roof coverings and are direct about the outcome. Where the covering has service life left and has failed at a detail, that is a repair. Where it has reached the end of its life, repeated patching is more expensive than replacement and we will say so.
Where material is loose or water is entering, the first priority is removing the risk and limiting further damage. What can be done safely on the day depends on wind, on rain and on access — a roof in an exposed position in a gale is not a place to be, and we would rather tell you that than take a chance.
We inspect the damage and provide a written quotation for the roofing work required. Insurers ask what happened, what the damage is and what it costs to put right, and an accurate description serves a claim better than a vague one.
Cover itself is between you and your insurer. Policies differ, and we do not make promises about someone else's contract.
Because gusts are rapid pressure changes rather than steady load. A fixing that holds against constant pressure can be worked loose by repeated sharp tugs, which is what turbulent air downwind of high ground delivers.
It can. Air accelerating over a ridge becomes turbulent on the lee side, and turbulent air is harder on roof coverings than smooth air of the same average speed.
It is common. The ridge sits where suction is strongest and has no course of tiles above it for protection, so it is usually the first part of a roof to give way.
Often yes. Without a working flue drying it out, a stack stays damp and the mortar weathers faster, so unused stacks can be in worse condition than they look.
That is usual. Water can travel some distance along battens and rafters before it drops, so we trace it back rather than repairing above the stain.
Yes. Dry-fix systems are made of components, and storms break components. Usually the affected parts can be replaced without disturbing the rest.
Where it is safe to do so, yes. Temporary measures reduce risk and limit further water damage; the permanent repair follows when conditions allow, and we will always be clear about which we have done.
Five guides written specifically for Caerphilly. We are publishing these in batches rather than all at once, so some are still being written — those are marked, rather than linked to a page that is not there.
We cover fifteen areas from our base in Neath. If yours is not listed, call and ask — the list is where we work most, not a boundary.
Tell us what the weather has done and what you can see from the ground. We will assess the roof, explain what needs repairing and give you a free, no-obligation quotation.
Tell us what the weather has done and what you can see from the ground. We will come back to you — usually the same day.
If water is coming in now, please call rather than email — 07766 547309.
