Ridge Tiles & Dry Ridge Systems

The ridge is the highest and most exposed point of a pitched roof, the apex where the two roof slopes meet. Ridge tiles cap this junction, shedding water away from both sides and preventing wind-driven rain from entering the roof void. Because they sit at the top of the roof with no tile above them to shed water on their joints, the way they are fixed and sealed is critical. Get it wrong and you will have persistent leaks at the very point that is hardest to diagnose from inside the loft.

Two Methods: Mortar Bedded vs Dry Ridge

Mortar-bedded ridge tiles (the traditional method) are set in a bed of sand-cement mortar over the ridge board or over the top course of tiles. The mortar fills the gap between the curved underside of the ridge tile and the roof surface on both sides, and the joints between individual tiles are pointed with mortar.

Dry ridge systems hold the ridge tiles in place without mortar: brackets fixed to the rafters carry a ridge batten, a continuous roll-out membrane seals the ridge, and each tile is screwed or clipped to the batten, with union strips covering the joints between tiles.¹ The system is flexible, accommodates thermal movement, and does not crack.

Since the 2014 revision of BS 5534, the code of practice for slating and tiling, ridge and hip tiles should be mechanically fixed even where they are also bedded in mortar.² Dry ridge kits are now covered by BS 8612:2018, the specification for dry-fixed ridge, hip and verge systems.²

Why Mortar Fails

Failed ridge mortar is one of the most common roof defects in the UK. Here is why:

• Thermal movement: ridge tiles heat and cool dramatically through the seasons. Clay and concrete expand and contract; mortar does not flex and eventually cracks.
• Freeze-thaw: water enters hairline cracks, freezes, expands, and widens the crack. After several winters, the mortar crumbles or detaches entirely.
• Poor original specification: many older ridges were bedded in a weak or poorly mixed mortar, which degrades faster than the tiles themselves.

A well-laid mortar ridge on a sheltered roof might last 15–25 years. On an exposed site, 10–15 years is more realistic. Over the life of a roof covering, a mortar-bedded ridge often needs re-bedding more than once.

Ridge Tile Types

Clay ridge tiles generally weather better than concrete and are preferred on natural slate or clay tile roofs. Concrete ridge tiles are more affordable but can look mismatched on a natural slate roof and will eventually suffer from surface erosion.

Cost: Re-Bedding vs Dry Ridge

Re-Bedding Mortar Ridge Tiles

Re-bedding involves chipping off the old mortar, cleaning the tile bedding area, applying new sand-cement mortar (typically a 3:1 sand-cement mix with a proprietary additive), re-pointing all joints, and adding a mechanical fixing to each tile so the work follows current BS 5534 practice. Existing ridge tiles can usually be reused if they are undamaged.

Cost table (supply and fix, ex-VAT):

The new-tile rates are the re-bedding rate plus the tiles: clay half-round ridge tiles cost roughly £26–£30 per metre of ridge before VAT, and concrete ones £6–£10.

Dry Ridge System

A dry ridge system replaces mortar with mechanical fixings. A typical universal kit contains a roll-out ridge membrane, brackets that hold the ridge batten to the rafters, union strips and clamps for the joints between ridge tiles, and stainless steel screws that fix each tile to the batten; end caps or block ends finish the ridge.¹

Cost table (supply and fix, ex-VAT):

On these figures a dry ridge conversion costs about the same as a full mortar re-bed, and it avoids the repeat re-bedding a mortar ridge needs every 10–25 years.

Ventilated Dry Ridge: A Building Regs Consideration

One benefit of a dry ridge system that is easy to overlook is ventilation. Traditional mortar-bedded ridges are solid; dry ridge kits can incorporate a ventilation strip along the full length of the ridge, allowing warm moist air to escape from the roof void at the highest point. This is the most effective position for roof void ventilation.

Approved Document C says a roof meets the condensation requirement if it is designed in line with BS 5250, the code of practice on moisture in buildings (now the 2021 edition), and that ventilating a cold roof will satisfy it.³⁴ Depending on the underlay and roof design, that can mean high-level ventilation at the ridge as well as eaves ventilation. Some universal dry ridge kits provide a continuous 5 mm ventilation gap along the ridge at little extra cost.¹

If you are re-roofing completely (stripping back to bare rafters and re-tiling), fitting a ventilated dry ridge at the same time makes strong practical sense: the ridge tiles have to be mechanically fixed under BS 5534 anyway, and a dry ridge kit does that and can provide the roof ventilation that Building Regulations Part C may call for.

When to Repair vs Replace

Repair (re-point individual tiles):

• Only one or two tiles are loose or cracked
• Surrounding mortar is sound and well-adhered
• Roof is less than 10 years old

Re-bed the full ridge:

• Mortar is crumbling along more than 30% of the ridge
• Multiple tiles are rocking or have been displaced in wind
• Moss and lichen are growing into the mortar joints (sign of chronic moisture)

Convert to dry ridge:

• You are re-roofing the whole slope anyway
• The ridge has been re-bedded twice or more in the past 30 years
• The property is in an exposed location (coastal, hilltop, or open countryside)
• You want to add ridge ventilation

Finding and Vetting a Roofer

Ridge tile work is one of the most commonly quoted jobs in roofing, and unfortunately one of the most prone to unnecessary or shoddy repairs. Before instructing any work:

1. Get at least three written quotes specifying whether the work is a re-bed, re-point, or dry ridge conversion
2. Ask the roofer to show you photographs of any loose or cracked tiles before work begins
3. Confirm how the work will be done safely at height: HSE guidance is that sloping roofs require scaffolding to prevent people or materials falling from the edge, with ladders and roof ladders only for short jobs measured in minutes⁵
4. Check NFRC membership or equivalent trade body
5. Ensure they provide a written guarantee, and compare the terms offered for mortar bedding and for a dry ridge system

Doorstep Offers

Ridge tile repair is one of the most common triggers for unsolicited doorstep approaches, particularly after storms. A stranger who knocks claiming your ridge tiles are “about to fall off” is almost never acting in your interest. Commission an independent inspection from a NFRC-registered roofer before agreeing to any repair from a cold caller.

Matching Existing Tiles

If re-bedding or replacing individual ridge tiles, colour and profile matching matters. Ridge tiles fade over time, so a new tile in the same product code can look obviously mismatched against weathered tiles. Options:

• Source reclaimed ridge tiles from a salvage yard that closely match the existing colour and profile
• Replace the full ridge length so the new colour is consistent
• Ask your roofer to source “pre-weathered” tiles from specialist suppliers, some manufacturers offer aged finishes for exactly this purpose

The rules in this note are those that apply in England. Scotland, Wales and Northern Ireland have their own building standards and permitted development rights.