Verge mortar
Why is mortar falling out of my roof verge?
The short answer
Mortar falls out of a verge because the bed under the edge tiles has cracked, shrunk or washed away after years of wind and rain. It is a warning rather than a cosmetic fault, because that mortar seals the gable edge and steadies the end tiles. A sound verge can often be raked out and repointed. If the tiles have loosened too, the edge needs rebuilding with a mechanical fixing.
Why a verge sheds its mortar, what the gap tells you about the tiles beside it, and how a roofer decides between pointing and rebuilding.
What the mortar at a verge was doing
On a gabled house the roof ends at a wall that rises to a point, and the last line of tiles running up the slope is the verge. Those tiles sit on a strip of mortar bedded along the wall head, usually over a narrow ledge of slate or tile called an undercloak.
That bed has two jobs. It fills the space between the final tiles and the masonry, shutting out wind and driving rain. It also gives each edge tile a firm seat at the right height, so it does not rock or tip outwards in a gust.
The outer face is open to the weather, so the bed is the one part of the roof you can watch deteriorate from the pavement. Grit on the path below the gable, or a dark line where pointing used to be, is often the first hint. Our guide to dry verges shows how the same edge is built without any wet bed.
Why the bed lets go on the gable edge
A verge takes weather from the side and from above. Driving rain finds hairline cracks in the mortar, and in cold spells the water inside swells and pushes flakes off the face. Season after season the bed also shrinks away from the wall and from the underside of the tiles, so the joint loosens even where it still looks whole from below.
Movement plays a part too. A masonry gable and a roof timber do not expand and contract at the same rate, and the verge sits right on the line between them. Old sand and cement beds are hard and brittle, so they crack instead of flexing. Where a verge was patched before, the new pointing sometimes fails because it went over dusty, loose old bed that never gripped.
Gales finish the job. Marley warns of severe suction on a windward slope pitched under 30 degrees, so a gently pitched bungalow can start shedding mortar after one hard blow.
Leaving a crumbling verge for another winter
A bare patch on the verge is not an emergency by itself, but it should not be left to run on. Once the bed is gone, wind and rain reach under the edge tiles, wet the timber at the gable and lift the tiles a little more with each gust. Edge tiles are also the ones that drop onto a path or into a neighbour's garden.
From the ground, look for a tile sitting tilted against its neighbours, daylight between a tile and the wall, or a dark stain on the gable brickwork beneath. Binoculars or a phone on zoom help, and a dated photograph gives you something to compare after the next storm. Please stay off the roof, and keep ladders away from an edge that already looks loose.
Loose tiles at an edge are the kind of fault we move up the list, and we make a roof safe before we talk about the lasting repair.
Pointing it back, or rebuilding the edge
If the tiles are tight, the wall is sound and the damage is confined to the face of the bed, the old mortar can be raked out and the edge repointed. It is a modest job and it often holds for a good while. The aim is a full bed that fills the gap, not a skim of cement smeared across the front.
If tiles have shifted, if the bed has dropped out along most of the run, or if the edge has been repointed more than once already, a patch will not last. The verge tiles come off, the old bed is chipped out and the edge is laid again. A roofer working to BS 5534 adds a mechanical fixing to each tile, and Marley advises a mechanical fixing for each bedded tile and fitting, so the mortar seals the joint without taking the load.
A dry verge is the other route. Clips hold the tiles, an end unit closes the gap, and no wet bed is left to crack. Marley is clear that following BS 5534 is not a legal requirement, so a good roofer will explain which route suits your gable.
What the survey and the quote cover
We look at the verge from the ground first, then from a ladder or tower where that is safe, and photograph each fault. Our written quote is one total, with survey pictures and a plain verdict attached: point it, rebuild it, or fit a dry verge.
Access often changes the job more than the mortar does. Reaching a gable two storeys up calls for a scaffold or tower, and where it stands over a pavement the highway authority may need to license the scaffold. West Sussex County Council wants a minimum of 10 working days' advance notice, so it helps to know early. Make sure any price you are handed has VAT and scaffold counted in.
Our page on dry verge costs sets out typical figures, and a tight quote should still leave room for any timber repair the survey finds. The main ridge tile repairs service page explains the wider work.
Related questions
Verge repair questions
Can I push new mortar into the gap myself?
A small gap at a low gable can look easy, but the bed behind the face is what matters, and it has to be raked out, cleaned and filled completely. A surface skim crumbles again. Working at the edge of a roof is also where falls happen, so photograph it and send it to us for a verdict instead.
Does missing verge mortar mean the rest of the roof is failing?
Not usually. The verge is the most exposed edge, so it often shows wear before the main field of tiles does. Check the slope from the ground for slipped or cracked tiles, and look in the loft for daylight or damp patches. If those are clear, the verge alone is probably the job.