At a gable, the roof slope ends at the wall, and the finish along that rising edge is called the verge. On most houses with gables that finish is a bed of mortar, trimmed and pointed, and it is one of the first parts of the roof to show age. Cracks run along it, pieces drop onto the path, the tiles above lose their support, and rain starts to find its way in at the edge. Because the verge is a visible line, the damage is easy to spot from the street, and because it is a few metres up, it is hard to judge from the ground. This guide explains how a mortar verge is built, why it cracks, how the repair options compare and where the borderline between repointing and a full rebuild falls. If your problem is at the ridge or hips instead, those have their own pages, and the wider subject sits under ridge and verge repairs.
How a mortar verge is built
At a gable, the roof covering has to end somewhere. The last rafter, the verge rafter, sits just inside the gable wall, and the tiles run slightly past the wall face so rainwater falls free of the brick or stone below. That overhang is where the verge detail is made.
Beneath the overhanging tiles sits an undercloak, a thin course of tile, slate or a strip of fibre-cement board laid along the edge. It provides a flat, firm surface for the mortar to rest on and tilts the water back onto the roof. On top of the undercloak and beneath the edge of the last tiles, a bed of mortar is laid. The verge tiles are pressed into it, then the face of the mortar is struck off and pointed. Sometimes a special tile, wider than the usual one, is used at the edge so the pattern of joints stays regular.
So there are three layers to a mortar verge: the undercloak below, the mortar bed between, and the tiles above. When people say the verge is cracked, they usually mean the mortar. But the mortar depends on the other two layers. A rotten or missing undercloak removes the support the mortar needs, and tiles that have slipped or lifted take the mortar with them.
It is also an exposed detail. The verge faces the weather on its outer edge, where wind driving up the slope can lift tiles, and rain runs off the wall into the mortar joints. Nothing about this makes failure unusual, only expected over time. What matters is knowing which layer has gone, and that comes from a close look.
Why verge mortar cracks and falls out
The commonest cause is simple ageing. Mortar contracts as it cures and shrinks a little more with each cycle of wet and dry weather, and thin hairline cracks develop at its edges. Rainwater enters them and, in winter, freezes and widens them. Once pieces start to break away, the process quickens, because each gap exposes more of the bed.
The mix matters. Mortar that is too strong or too rigid for the tile and the wall can crack where it meets them, since it does not accommodate small movements. Mortar that is too weak or too wet when laid can crumble early. A fresh bed laid over dust and loose material will not bond. On older roofs the original bed may have been lime-based, and a later cement patch can pull away from it, because the two behave differently. Our page on lime mortar on ridges deals with that question on traditional roofs, and the same principle applies to verges.
Movement in the structure is another cause. A gable wall that has settled or leaned a little changes the gap between wall and roof, and the mortar between them cracks to take it up. If a crack keeps reopening, or runs in a stepped line down the gable, the cause is not the verge but the wall, and repointing will not hold.
Finally, there are missing fixings. A mortar verge laid without mechanical fixing relies on the bond between mortar and tile, which is the weak point. Under BS 5534:2014 verge tiles should have mechanical fixings in addition to their mortar bedding, so a verge that is only mortared is not built to the standard now expected. When the mortar gives way there is nothing else to hold the edge tiles, and in a gale the edge can start to lift.
Reading the damage: what is cracked, what is missing
From the ground, three patterns tell most of the story. A fine crack along the length of the verge, with the mortar still in place, points to early shrinkage or a bond failure. Missing chunks, with the tile edges showing, mean the mortar has crumbled. Tiles that sit proud or tilted at the edge suggest the bed beneath them has gone or the undercloak has moved.
Once we are up at the edge, the inspection gets closer. We tap the mortar to hear whether it rings or sounds hollow, which tells us how far a failed bond extends beyond the visible crack. We look at the undercloak where it can be seen, since a split or rotted strip shows as a dark, crumbling line. We check the verge rafter for movement, and the gable wall for cracks, bulging or loose stones at the top. If the wall coping or the top courses are loose, that needs sorting before any roof work is trusted to it.
In the loft, it is worth checking the verge end for damp staining or daylight. Water that enters at a verge often shows up on the timbers a short way in, not at the edge, so the first sign may be a tide mark on the gable-end rafters or a damp patch on the ceiling near the wall.
Photographs of all this go into the survey. The point is to give you evidence for what is wrong, and a way of understanding the scope of the repair before it starts. A verge can be sound for most of its length and failed for a single stretch, in which case the repair is limited to that stretch. If the damage runs from end to end, the whole verge needs doing. We would rather show you which of these applies than leave you to take it on trust.
Repair options: repoint, re-bed or rebuild
Three routes cover most verges, and the survey decides which fits.
Repointing
Where the mortar bed is sound beneath and only the surface has cracked or eroded, the loose mortar is raked out and fresh mortar is pointed in. It is the least costly option, but it only works if the bed behind the surface is firm. Pointing over a hollow bed looks fine for a short while and then falls. Our page on repointing ridge tiles covers the same technique for ridges.
Re-bedding the verge
If the bed is hollow or crumbling, the edge tiles are lifted, the old mortar is cleared down to the undercloak, and the tiles are laid again on a new bed with mechanical fixings. The undercloak is checked and replaced where it has rotted or split. This is the normal repair for a verge in poor but not hopeless condition, and it follows the same principles as a ridge re-bed: clean surface, full bed, fixings into sound timber. The verge undercloak has a page of its own, verge undercloak, for the detail.
Rebuilding
Where tiles are cracked or missing, the undercloak is gone and the gable wall top is loose, the whole verge is taken apart and rebuilt. The wall top is made good first, a new undercloak goes on, and the tiles and bed follow. It is more work and costs more, but it is the only repair that does not store up the same fault.
Each route ends with the mortar finished neatly, struck off flush and kept off the faces of the tiles. Colour is matched to the tile and the wall, so the line looks of a piece with the roof. On an older roof the mortar mix is chosen to suit the building, not just the repair.
Dry verge systems as an alternative
A dry verge swaps the mortar for a mechanically fixed trim. A cap or cloak, usually plastic, is clipped or screwed along the edge, holding the last tiles and shedding water away from the wall. No mortar means nothing to crack and nothing to repoint later. Systems of this kind are assessed to BS 8612:2018. We compare the options, with the points for and against, in dry verge systems, and the costs have a page of their own at dry verge cost.
Dry verges suit roofs where the mortar keeps failing, where the gable is hard to reach for repeat visits, and where the look of a plain trim is acceptable. They are not the right answer everywhere. On a listed house, or along a street where mortar verges are part of the character, the change shows and may need consent. They also depend on the condition of what is below: a dry verge fixed over a rotten undercloak or a movement crack will not cure either.
Where a roof already has a dry verge that is causing trouble, our page on dry verge problems sets out what goes wrong and how it is fixed. For a mortar verge on an ordinary house, a re-bed with fixings will often be enough, and the roof keeps the look it has. We say which route we would choose for your roof, and why, in the written survey.
Roof, house age and owner preference all bear on the choice, so we do not push one system. The aim is a verge that is dry, firm and consistent with the rest of the roof.
Verge damage, insurance and what to do now
If mortar has fallen or a verge tile has come loose, the first step is safety. Mortar and tiles drop on the path or the neighbour's side, so the area beneath is kept clear. A loose verge tile in wind is a hazard, and we make it safe first, which may mean removing or securing the tile before a proper repair.
Photographs help. If the damage followed a storm, take pictures of the verge, the debris and any water that has come in, with the date. They support an insurance claim if you make one. Insurers commonly distinguish between storm damage and wear and tear, and a verge that has crumbled over years can end up on the wear side of that divide. We explain that distinction, without promising any outcome, on the page about ridge tiles and insurance, and the same reasoning applies to verges.
A temporary measure can stop water getting in while a repair is arranged, such as a protective sheet fixed securely over the damaged edge. It should be done by someone who can reach the verge safely. Please do not climb up to do it yourself: a verge is at the edge of the roof, which is where falls happen.
When you are ready, a survey tells you the extent of the fault and which of the repair routes fits. You receive photographs of your own verge, a fixed price in writing, and a plan that deals with the mortar, the undercloak and any fixings in one visit. Afterwards the site is left clear and the waste is taken off, and a quick look along the verge from the street after the next storm confirms the tiles have stayed put. To book the survey, ring 01225 285181 or use WhatsApp or the form on this site.