Look at the side of a gable-ended house and you will see the sloping edge where the tiles stop and the brick wall carries on up to the ridge. That edge is the verge. It is the neatest line on the roof and one of the most exposed, because wind catches it from the side and from below. Done properly, a verge is tight and invisible. Done badly or left to age, it cracks, lets in water and lets go of its tiles. This page explains the parts of a verge, how they fail, and how a repair is carried out step by step.
What a verge is made of
A mortar-bedded verge has four layers you can name. At the bottom is the gable wall, the brickwork that rises to follow the slope of the roof. On top of the wall sits the undercloak: a strip of material, often fibre cement, slate, or a course of plain tiles, laid with a slight overhang beyond the wall so water drips clear of the brickwork. The roof tiles then run to the edge and sit over the undercloak, and the gap between the last tile and the edge is closed with a bed of mortar, sometimes finished with a verge tile. The result looks like a mortar fillet running up the gable.
The answer on what verge undercloak is goes into the materials, and the page on what a roof verge is covers the basics for anyone who only wants the definition.
Why verges fail
A verge combines three weak points: it is on the edge of the roof, it relies on mortar, and it is hard to see from the house. The usual failures follow a familiar pattern.
Cracked and crumbling mortar
The bed between the tiles and the wall is exposed to rain on both faces and to frost. It cracks along the junction with the brickwork, then loses its grip on the tile edge. Sections fall away, often a hand's length at a time, and the end tiles start to lift.
Undercloak that has rotted or slipped
Older undercloak in timber or poor board can rot. Fibre cement can crack or become brittle. Where the undercloak has dropped, water finds the top of the wall and the brickwork under it grows damp, and the end tile loses its support.
Tiles lifting in the wind
If the end tiles are held by nothing but mortar, a strong gust can lift them. A single tile that sits slightly raised at the verge is a warning. A line of tiles that move together is a larger fault and can put a section of roof at risk.
Wall damage behind the verge
Water getting into the top courses of the gable can cause the pointing to fail and the brick to spall. Repairs to a verge sometimes reveal that the wall needs a course relaid before the edge can be rebuilt.
How a mortar verge is repaired
The process depends on how far the damage goes. We separate it into three levels.
Re-pointing a sound verge
If the tiles are firmly held and only the surface of the mortar has weathered, the repair is to rake out the loose bed, clean the joint, and refill with a mortar mix chosen to suit the roof tile. Colour matching matters, because a verge shows from the street. This is the lightest repair, and it only holds if the underlying bond is good.
Re-bedding the end tiles
If the end tiles rock, we lift them, clear the old bed, check the undercloak and the top of the wall, and re-lay the tiles on fresh mortar. Each tile gets a mechanical fixing, because BS 5534:2014 expects verge components to be fixed and not trusted to mortar alone. The rule is explained in our guide to BS 5534 and BS 8612 for ridges.
Full rebuild
If the undercloak has failed, the wall top is damaged, or the whole run is loose, the verge is stripped back and rebuilt. The steps are: take off the end tiles and the old bed; repair the brickwork if needed; fix new undercloak with a proper overhang; lay the tiles back with mechanical fixings; and finish the edge with fresh mortar or a verge system. It is the longest job but the one that ends the cycle of patching.
The steps of a typical repair
A repair day on a verge usually runs like this. We set up safe access, because a verge sits at the edge of a roof and needs a scaffold or a tower. We check the condition of the verge from above and mark the sections to be repaired. We remove loose and failed material, taking care not to disturb the sound sections. We inspect the undercloak and the top of the wall and repair them if they need it. We re-lay or re-bed the tiles with mechanical fixings, then finish and tool the mortar so water sheds from it. Finally the tiles and ground are cleared of debris, and the waste is taken away.
The work is weather-dependent. Mortar should not be laid in hard frost or in heavy rain, and in cold snaps we may time the job to suit. If the roof is open at the end of a day, we protect it so rain cannot get in overnight.
Mortar or dry verge?
Dry verge is a system of preformed end units, usually in plastic or a similar material, that clip or screw to the end of the roof and cover the edge without mortar. They are fixed mechanically, are quick to fit and need no pointing. The standard for dry-fix systems is BS 8612:2018.
Dry verge suits a roof where the existing mortar has repeatedly failed, where the verge would otherwise have to be rebuilt, or where the owner wants a low-maintenance edge. It is less suited to a period house where the look of a mortar fillet is part of the character, or where the council expects traditional materials. Our guides to dry verge systems: types, fitting and problems and fitting dry verge to an existing roof go through the choices. There is no reliable published price for a dry verge, so we do not print one. The fixed written quote after the survey gives the figure for your gable.
| Condition found | Usual repair | Why |
|---|---|---|
| Weathered mortar, tiles firm | Re-pointing | Bond is good, only the surface has aged |
| End tiles rocking | Re-bed with fixings | Mortar has lost its grip |
| Undercloak cracked or rotten | Rebuild the edge | Water reaches the wall top |
| Repeated failure, mortar looks wrong for the house | Dry verge | No wet bed to crack |
Signs a verge needs attention
You can judge a verge from the ground, in the same way as a ridge. Look along the gable edge for a continuous, even line of mortar. Pale, sandy or cracked patches, missing sections, and a gap between the mortar and the wall are the early signs. Look at the end tiles for any that sit higher than the rest or that have shifted towards the edge. Look at the wall below for dark streaks, green growth or damp patches that follow the line of the verge, which show where rain has been running into the brickwork instead of dripping clear.
Inside, a damp patch at the top of the gable wall in an upstairs room, or a stain where the wall meets the ceiling, can come from a failed verge. In the loft, check the timber at the edge of the roof, the bargeboard or the wall plate nearest the gable for dark staining and soft wood. Small signs are worth acting on, because a verge that has started to fail does so faster each winter.
Common mistakes in verge repairs
A few poor habits cause most repeat failures. Smearing new mortar over old, loose bed gives a good-looking result that falls off within a year. Using a mix that is too strong or the wrong colour looks bad and cracks away from softer tile. Leaving out the undercloak, or building over one that has rotted, hides the cause of the damp. Filling gaps with sealant or foam instead of mortar may hold for a season, but it traps water and fails in sun and frost. And fixing only the tile you can see leaves the next one to follow. Ask any roofer who quotes for verge work what they will do about each of these.
Regulations, listed buildings and neighbours
A small repair to the verge does not normally need building control approval. A larger job that changes a large share of the roof covering can, so we check the Planning Portal thresholds on the survey. Swapping a mortar verge for dry verge alters how the gable edge looks, which matters on a listed house or inside a conservation area, and speak to the conservation officer at your council before you agree to it.
Gable walls on semi-detached and terraced houses are often shared. Work on the verge of a shared wall may involve the neighbour's roof, and a courteous word before the scaffold goes up saves trouble. We can advise on what to say.
How to look after a verge once it is done
A repaired or rebuilt verge should not need much. Look at it from the ground each autumn after the leaves have fallen and each spring after the winter wind. Check for gaps at the end tiles, for moss pushing into the joint and for stains on the gable wall below. Trim back any branches that rub on the edge. Do not pressure-wash the mortar. Our page on whether pressure washing damages roof tiles explains what high pressure does to joints.
When you ask us to look, the free survey comes with photographs of your own verge, and one fixed written quote follows it. Where a patch repair will do, we say so. Rebuilt verges carry our ten-year workmanship guarantee, written down, and the site is left clean. More on this kind of work is on our ridge tile repairs in Basingstoke page, and the quickest route to a visit is a call to 01256 213956 or a message on WhatsApp.
