The verge is the edge of a tiled or slated roof where it finishes at a gable wall, the triangular end wall of the house. The last row of tiles juts a little past the wall and sits in mortar, on a concealed strip called the undercloak. That mortar is what you see from the road: a pale line along the sloping edge of the gable.
Of all the roof edges, this one tends to show age early. This guide explains why mortar verges crack and fall, how to tell a pointing repair from a rebuild, what a rebuild on new undercloak involves, and when we would suggest changing to a dry verge. Dry-fix products as a family are covered in the ridge, verge and dry-fix hub.
How a mortar verge is built and why it is exposed
At a gable there is no gutter and no eaves to shed water, only the stone or brick wall below and the roof edge above. The roof covering stops a short way beyond the wall face, so that rain running down the last tile drips clear instead of tracking back across the masonry. Under that overhang sits the undercloak, a narrow strip laid on the wall head to support the underside of the verge tiles and to close the gap between the tiles and the wall.
The verge tiles themselves are laid on a bed of mortar over that strip. The mortar fills the space between the tile and the undercloak, seals the edge against wind-driven rain, and gives the tile a solid seat. It is not decorative. It is the weathering of the roof edge.
Why this edge is hard on mortar
A verge is the roof's most exposed line. Wind gets underneath it from the side, rain hits it from both faces, and the mortar is thin, with a lot of surface area for its volume. Nothing shelters it. The wall below and the timber behind it expand and contract at different rates from the mortar between, so hairline cracks open along the edges of the bed.
The sequence of failure
It usually starts with fine cracks at the junction between mortar and tile. Water enters, freezes in a cold spell, and widens the crack. A piece of mortar drops out and the tile above it loses support along that stretch. After that, wind starts to work on the tile itself. A verge in this state is not just untidy: tiles can come loose at the edge of the roof, directly above a path or a neighbour's garden.
Reading the signs: cracks, gaps and stains
Many verge faults can be spotted from the pavement with binoculars on a dry day.
What to look for
Fine cracks in the mortar line are the mildest sign. Wider cracks, dark gaps where the mortar has pulled away from the tile, and chunks of missing mortar all show a bed that is failing. Tiles at the edge that sit at a different angle from their neighbours, or that sit proud of the wall, have lost their seat. Green or dark staining down the gable wall below the verge shows that water is getting in or running down the face.
Signs inside
Inside the house, damp patches on the upper wall of a gable bedroom, or staining on the loft side of the gable, may trace back to the verge. A damp gable sends us to the verge first, because the roof edge is a likely source before the wall itself.
Separating cracks from failure
Not every crack means the verge has failed. A hairline crack in an otherwise firm bed can be raked out and repointed. A crack that runs with a tile that rocks, or a mortar bed that sounds hollow when tapped, means the bed has stopped gripping. The test on the roof is by hand, tile by tile, from the ridge end to the eaves.
The difference matters for cost. MyBuilder's roof repair guide, updated August 2026, describes minor repairs at £100 to £300 and moderate ones at £500 to £1,000. A verge repair can sit at either end depending on how much has to come off, and the figure for your gable follows the survey.
Undercloak: the hidden board that decides how long the verge lasts
The undercloak is the layer most people never see, and it explains why some verges last and others crumble. Our answer on the verge undercloak defines the board itself. For repairs, the point is what its condition tells us.
Materials
Undercloak is usually a strip of fibre cement, a course of plain tiles or slates, or on older work a timber board. It is fixed to the wall head and the end of the battens. Timber rots if it is damp for long, fibre cement can crack, and a tile or slate course is only as good as its fixing.
What goes wrong
When the undercloak has dropped, split or rotted, the mortar loses its support and falls with it, and replacing the mortar alone cannot hold. We often find old undercloak that is perfectly serviceable under badly cracked mortar, and sometimes a good-looking verge sitting on rotten board. We cannot tell from the ground, so the tiles come off to see.
The battens behind
The batten ends at the gable are inspected at the same time. The last batten carries the verge tiles, and if it has rotted where it meets the wall, new mortar will not hold the tile either. Replacing a batten end is a small job when the verge is open and a bigger one when it is not.
If the undercloak is sound and fixed, a verge can often be rebuilt on it. If it has failed, replacing the undercloak is the repair, and the mortar follows from that.
Rebuilding a verge, step by step
A full rebuild takes the verge back to the structure and builds it up again. The steps are the same on a terraced gable in Stroud as on a detached house in a village.
1. Stripping
The verge tiles are removed from the ridge end down, with the old mortar chipped off the tiles and the wall head. Debris is bagged and kept off the slope. Sound tiles are cleaned and kept in order, and cracked ones are put aside to be replaced with the closest match.
2. Checking the structure
With the edge bare, we look at the wall head, the batten ends and the barge area. Loose brick or stone at the top of the gable is rebuilt first, since a verge cannot sit on a crumbling wall. Rotten batten ends are cut out and renewed.
3. Fixing new undercloak
A new undercloak strip is fixed along the wall head, tight to the battens and set to project the correct amount for the overhang. Where the old one is sound, it stays.
4. Bedding and fixing the tiles
The verge tiles are bedded on fresh mortar, set with a modest overhang so water drips clear of the wall, and fixed mechanically. BS 5534, in its 2014 revision, no longer treats mortar alone as enough to hold verge, ridge and hip tiles, and each verge tile is fixed as well as bedded. The tiles are lined up with a string so the edge is straight along its whole length.
5. Pointing and finishing
Joints are pressed and finished, excess mortar removed and tile faces cleaned. The verge meets the ridge at the top: that junction is rebuilt with it, since a new verge against an old failing ridge end is a weak join. For the ridge itself, our storm-loose ridges guide explains how loosened ridge tiles are made safe and repaired.
Cracks and pointing: when a lighter repair is fair
Repointing is the cheaper repair and sometimes the right one. If the verge tiles are tight, the undercloak is sound and only the surface of the mortar has weathered, raking out loose material to a good depth and filling with fresh mortar can give the verge another few years.
What decides it
Three tests settle the choice: do the tiles move when pressed, does the mortar sound hollow, and is there any sign of water behind the edge. If the answer to all three is no, we are looking at a pointing job. If any is yes, repointing seals a surface that is already letting go underneath.
Why patching fails
Fresh mortar poured over loose old material does not bond. It looks fine for a season, then it cracks along the line where it meets the old bed. Patches also leave a visible join in colour and texture. We would rather tell you that a section needs rebuilding than quote a patch that will be back on the list next winter.
Colour and finish
Verge mortar is a visible line, and a new section that is too white or too grey stands out. We match the colour of the mortar to the existing work as closely as the weathering allows, and the survey photographs help us agree what the finished edge should look like. On protected buildings, lime mortar may be required; see our guide to lime-bedded ridges on period roofs for how that changes the work.
When to switch to a dry verge
Swapping to dry means a factory-made profile fixed to the roof in place of the mortar bed. Continuous systems run along the whole edge, and unit systems fit tile by tile. Tested products follow BS 8612.
Reasons to consider it
Mortar verges are the first thing to go on many gable roofs. If the verge has failed more than once, if access to repeat the repair is difficult and costly, or if the work would otherwise run into a cold spell, a dry verge removes the mortar from the equation. It does not rely on a bed that must keep gripping and, once fixed, needs less upkeep.
Reasons to hesitate
A dry verge looks different. The edge is a plastic or metal profile and not a bedded tile finish, and on some older roofs it will not suit the tile profile. In a conservation area or on a listed building, appearance matters and consent may be needed. Some of the district's conservation areas, including two in Stroud itself, carry Article 4 Directions, and the council does not spell out whether they reach roofs. The planning team is the one to ask before the finish changes.
Pricing the choice
We price both where the roof allows. A rebuilt mortar verge and a dry verge differ in what they cost now and what they ask of you later, and the quote can cover either, with scaffold, labour, materials and waste. Our 10-year workmanship guarantee is written down, and the site is left clear.