Re-bedding Ridge Tiles: Mortar vs Dry-Fix Systems

Quick Answer: Since BS 5534 was revised (the 2014 update, with subsequent amendments), ridge and hip tiles must be mechanically fixed as well as bedded — mortar alone is no longer an acceptable means of fixing on a re-roof or new roof. You can re-bed in mortar but must add mechanical fixings (ridge screws/clips), or fit a dry-fix (dry ridge) system that needs no mortar at all and provides ventilation and a mechanical fix in one. Dry-fix is now the default on most pitched-roof work because it is BS 5534 compliant out of the box, weatherproof immediately, and not dependent on the weather or the skill of the bedding. Re-bedding in mortar without mechanical fixing does not meet the current code of practice.

Summary

Ridge tiles cap the apex (and hips) of a pitched roof, sealing the junction where the two tiled slopes meet. Traditionally they were bedded in sand-and-cement mortar, which both held them down and weatherproofed the joint. Decades of experience showed the weakness: mortar shrinks, cracks, and lets go in freeze-thaw and high wind, and loose ridge tiles are a common cause of leaks and a serious falling hazard. This drove the change in BS 5534, the British Standard code of practice for slating and tiling, which now requires ridge and hip tiles to be mechanically fixed in addition to (or instead of) being bedded.

That single change reframes every ridge job. On a re-roof or new roof you cannot simply bed ridge tiles in mortar and call it done — they must be mechanically secured with ridge screws or clips, or installed using a dry-fix system. For a repair or partial re-bed on an existing roof, good practice is to bring the work up to the current standard by adding mechanical fixing, even if the original was mortar-only. The two routes are: re-bed in mortar plus mechanical fixings, or strip the mortar and fit a dry ridge system.

Dry-fix (dry ridge) has become the default. A dry ridge system uses a roll of ventilated, weatherproof material under a metal or plastic ridge batten, with each ridge tile screwed or clipped down. It needs no mortar, so it is unaffected by weather during installation, it provides high-level ventilation that helps meet roof-ventilation requirements, and it accommodates thermal movement without cracking. Mortar bedding still has a place — heritage and conservation work, planning conditions requiring a traditional appearance, and matching existing roofs — but even then mechanical fixing is required under the current code.

Key Facts

• BS 5534 (Code of practice for slating and tiling) requires ridge and hip tiles to be mechanically fixed, not held by mortar alone, on new and re-roof work.
• Mortar alone is non-compliant for fixing on re-roofs/new roofs since the BS 5534 revision — mortar may bed, but a mechanical fixing must also be present.
• Two compliant routes — (1) mortar bedding plus mechanical ridge fixings (screws/clips); (2) a dry-fix (dry ridge) system with no mortar.
• Dry ridge systems combine a ventilated roll, a ridge batten, and mechanical fixing of each ridge tile — BS 5534 compliant by design.
• Mortar mix for bedding (where used) is typically a strong sand:cement mix (commonly around 3:1 sharp sand to cement) with plasticiser — follow the tile/mortar manufacturer's specification.
• Dry-fix advantages — weather-independent install, immediate weatherproofing, high-level ventilation, no shrinkage cracking, accommodates thermal movement.
• Mortar advantages — traditional appearance for heritage/conservation, may be required by planning or to match an existing roof.
• Ventilation — dry ridge can provide the high-level ventilation path required under Building Regulations Approved Document F / BS 5250 to control roof-space condensation.
• Work at height — ridge work is high-level; scaffold or appropriate access and edge protection is required under the Work at Height Regulations 2005.
• Don't mix systems badly — patch-bedding a few ridge tiles in mortar on an otherwise sound roof is acceptable as a repair, but bring fixings up to standard.
• Ridge tile types — half-round, angular (third-round) and modern interlocking ridges; the dry-fix system must suit the ridge profile and main tile.
• Inspect the bedding — cracked, hollow-sounding or vegetation-colonised mortar bedding indicates failure and the need to re-bed or convert to dry-fix.

Quick Reference Table

Detailed Guidance

Why BS 5534 changed

Following severe wind events and decades of ridge-tile failures, BS 5534 was revised so that ridge and hip tiles can no longer rely on mortar alone to stay in place. Mortar is rigid and brittle; it shrinks as it cures, cracks under thermal and structural movement, and degrades in freeze-thaw, eventually releasing the tile. The revised code requires a mechanical fixing — a ridge screw or clip engaging the ridge tile to a batten — so that even if the mortar fails, the tile is held. This is why a straight mortar re-bed no longer meets the standard on re-roof or new work.

Re-bedding in mortar (with mechanical fixing)

Where a mortar finish is required (heritage, planning, matching an existing roof), strip the old ridge tiles and clean off failed mortar. Set out a ridge batten fixed through the apex so ridge screws or clips can engage each tile. Bed the ridge tiles on a fresh, correctly specified sand:cement mortar (commonly around 3:1 with plasticiser, per the manufacturer), keeping a consistent line and full bed, then drive the mechanical fixing through each ridge into the batten. Point neatly and protect from rain and frost while curing. The mortar weatherproofs and gives the traditional look; the mechanical fixing satisfies BS 5534.

Installing a dry-fix (dry ridge) system

Fix a ridge batten along the apex at the correct height for the ridge profile and main tile. Roll out the ventilated dry-ridge roll, bonding or fixing its flanges down onto the top course of tiles each side to weatherproof the junction and leave a clear ventilation path. Lay the ridge tiles along the batten, butting the unions, and fix each with the system's ridge screws or clips into the batten. Fit ridge end caps and any block ends as required. The result is mechanically fixed, ventilated and weathertight immediately, with no mortar and no curing delay.

Choosing between mortar and dry-fix

Default to dry-fix for most re-roof and repair-to-standard work: it is compliant by design, weather-independent, ventilated, and low-maintenance. Choose mortar (with mechanical fixing) where appearance matters — conservation areas, listed buildings, planning conditions, or to match a partially re-bedded existing roof. Never specify mortar-only fixing on new or re-roof work; it does not meet the current code and is a recognised failure and safety risk. For a small localised repair on an otherwise sound mortar roof, re-bed the affected tiles and add mechanical fixing rather than converting the whole ridge.

Ventilation and the wider roof

A dry ridge can double as the high-level ventilation outlet needed to control condensation in the roof void, working with eaves ventilation to maintain airflow under Approved Document F and BS 5250. If you convert a mortar ridge to dry-fix, you may improve the roof's ventilation at the same time — useful where condensation or a sealed roof void is a concern. Coordinate ridge ventilation with eaves and any underlay type so the ventilation path is continuous.

Access, safety and inspection

Ridge work is at the highest point of the roof, so plan access under the Work at Height Regulations 2005 — scaffold with edge protection, roof ladders, or a tower as appropriate, never standing on the ridge unprotected. Before quoting, inspect the existing bedding: cracked, hollow-sounding, vegetation-colonised or missing mortar indicates ridge-tile failure and the need to re-bed or convert. Check the ridge tiles themselves for cracks and the batten/timber at the apex for rot before re-fixing.

Frequently Asked Questions

Can I still bed ridge tiles in mortar?

Yes, you can bed in mortar, but on a new roof or re-roof you must also mechanically fix each ridge tile with screws or clips — mortar alone no longer satisfies BS 5534. Mortar is typically chosen now for heritage, conservation or matching work where appearance matters. For most other work, a dry-fix system is simpler and compliant by design.

Is dry ridge better than mortar?

For most modern re-roof and repair work, yes. Dry-fix is BS 5534 compliant out of the box, can be installed in any weather, is weatherproof immediately, provides high-level ventilation, and does not crack or shrink. Mortar's advantage is the traditional appearance, which can be essential on listed or conservation-area roofs. Both are valid when correctly mechanically fixed.

Do I need to re-bed the whole ridge if only a few tiles are loose?

Not necessarily. A few loose ridge tiles on an otherwise sound mortar ridge can be re-bedded locally, but good practice is to add mechanical fixing to the repaired tiles rather than relying on mortar alone. If the bedding is failing along the whole ridge — widespread cracking, hollow sounds, vegetation — re-bed the full length or convert to dry-fix to bring it up to standard.

Does re-bedding ridge tiles need scaffolding?

Ridge work is at the highest point of the roof and is subject to the Work at Height Regulations 2005, which require suitable access and fall protection. In practice that usually means scaffold with edge protection, or an appropriate tower and roof-access equipment. Working off a ladder at the ridge without protection is not acceptable for anything beyond the briefest inspection.

Regulations & Standards

• BS 5534 — Code of practice for slating and tiling (including shingles): requires mechanical fixing of ridge and hip tiles in addition to/instead of mortar bedding.

• BS 5250 — Code of practice for the control of condensation in buildings: roof-void ventilation relevant to ridge ventilation.

• Building Regulations Approved Document F (Ventilation) — roof-space ventilation requirements that ridge ventilation helps satisfy.

• Building Regulations Approved Document C (Resistance to moisture) — weather-tightness of the roof covering.

• Work at Height Regulations 2005 — access and fall protection for ridge and roof work.

• NHBC Standards (Chapter on roofing) — workmanship guidance for new-build ridge fixing.

• BSI: BS 5534 slating and tiling code of practice (bsigroup.com) — mechanical fixing requirement for ridge and hip tiles

• NFRC technical guidance on ridge fixing (nfrc.co.uk) — National Federation of Roofing Contractors best practice

• Approved Document F: Ventilation (gov.uk) — roof ventilation requirements

• HSE: Work at Height Regulations 2005 (hse.gov.uk) — access and fall protection

• NHBC Standards (nhbc.co.uk) — workmanship standards for roofing

• dry verge and dry ridge systems — dry-fix ridge and verge systems in detail

• roof ventilation — high-level ventilation and Approved Document F

• pitched roof repairs — when partial ridge re-bedding is appropriate

• re roofing — full re-roof scope and bringing fixings up to BS 5534