What Is the Roll in a Dry Ridge Kit?

When a ridge was bedded in mortar, the mortar sealed the gap between the ridge tiles and the roof covering. A dry ridge has no mortar, so something else has to close that gap. The ridge roll does the job. It is a long strip, supplied on a reel, laid along the apex with its centre over the ridge and its wings spreading down onto the tiles either side. The ridge tiles then sit on top of it and are fixed down through or alongside it.

Why does it have to be ventilated?

A roof space needs air to move through it, or moisture from the house settles on cold timber. BS 5250 deals with moisture in buildings, and an opening at the ridge is one way a cold roof lets damp air escape. A ventilated roll is built so vapour can pass out through it while liquid rain stays out. Without that, a sealed apex can trap condensation against the ridge board and the tops of the rafters, where it is hard to spot until the timber is damp. Our page on the ventilated dry ridge explains the airflow in more detail.

Dressing means pressing the wings of the roll down onto the surface so they follow the shape of the tiles. This is the skilled part of the job. Roof tiles are not flat. Concrete interlocking tiles have ridges and troughs, and clay pantiles or double Romans have deep waves. The wing has to be pushed into those contours so it grips, with no bridges where air or water can slip underneath.

What does a well-dressed roll look like?

It sits tight along its whole length, with the self-adhesive edge pressed against clean, dry tile. Each join between two lengths is lapped by the distance the maker states and pressed firmly. At the ends, the roll is cut square and tucked against the closer or cap so that no raw edge is left open. The ridge tiles then go on top without squashing it flat, because a crushed roll loses the air gaps that let it breathe.

On a cold day, or on tiles with moss or dust on them, the adhesive can fail to take. Good fitting means cleaning the surface and choosing the right conditions, not rushing the dressing.

The roll relies on a seal that is only as good as its contact with the tile. If the adhesive edge lifts, wind-driven rain can blow underneath it and wet the batten and the timber beneath. The same happens where a lap is too small or has opened out, because the join is the weakest point on the strip.

What are the signs a roll has failed?

A dark strip hanging below the tile line is visible from the garden, as is a flap that moves in the wind. Inside, look at the ceiling near the ridge for staining, and check the loft for damp patches on the timber directly beneath the apex. Birds can lift a loose edge as well. A tile that rattles may be sitting on a roll that has crushed or slipped.

Poor fitting is the usual cause, and a cheap kit with a thin roll can make it worse. Our page on dry ridge failure sets out the other weak points, and the page on dry ridge unions leaking covers the joints where the roll meets the hip pieces.

Because the roll sits out of sight, it is easy to ignore when comparing quotes. It deserves a question. Ask which make of kit is going on, and whether the system has passed the BS 8612 tests for dry-fix. Ask how the roll is fixed to the tile, and how the laps are made. A roofer who can describe those details is likely to fit the roll with care.

Can a damaged roll be replaced without redoing the ridge?

Sometimes, but not always. The ridge tiles have to come off to reach it, and where the batten, brackets and tiles are sound, they are refitted over the new strip. If the roll has failed because the timber underneath is damp or the kit was a poor fit, a repair of one section only delays the next. We survey the ridge from above, show you photos of the roll and the timber, and then give you one written price.

Read more about the system in our guide to dry ridge and verge. A photo of any loose strip, taken from the ground, tells us a good deal before we go up.