Roofers and surveyors mention BS 5534 often, and it is easy to come away thinking it forbids mortar on a ridge. It does not. What changed is the weight placed on mortar. What changed with the 2014 revision is how much weight mortar is asked to carry. Ridge tiles and hip tiles are no longer left to the mortar alone; a clip, strap, screw or bracket grips each one as well, whether or not the bed beneath is sound.
The idea is simple. Mortar is strong in compression and weak when something pulls on it. A gale lifts a ridge tile upwards, which is just the direction mortar copes with least, so a second line of defence is sensible. BS 5534 is BSI's code for slating and tiling pitched roofs and vertical cladding, and the current edition is BS 5534:2014+A2:2018, published in February 2018.
Below we cover what the standard says in plain words, how mechanical fixing works with a bedded ridge and a dry one, what it means for old roofs and heritage buildings, and how it affects the cost and the survey. Our wider comparison of mortar and dry-fix sits alongside.
What the standard is and what it is not
BS 5534 is a code of practice, which means it sets out recommended good practice for how pitched roofs are covered with slates and tiles. It covers the tiles themselves, the battens that carry them, the underlay, the laps and the fixings. It is a document that tile makers, roofers, surveyors and warranty providers refer to when they ask whether a job was done properly.
It is not a statute. Marley states plainly that installing to BS 5534 is not required by law. Yet it carries weight in the trade, because it is the benchmark a competent roof is measured against. If a roof fails and the work did not follow it, that is an uncomfortable position for the person who fitted it.
The 2014 change in plain words
Marley's reading of the 2014 revision is that mortar is too weak in tension to be the sole fixing for ridge and hip tiles, so anything bedded should also be held mechanically. In the years before, a mortar bed by itself was still the usual, accepted method. In practice that means ridge and hip tiles now carry a mechanical fixing as well as their bed.
Marley adds that single-lap tiles and ridge and hip tiles were all to be fixed mechanically whatever mortar was used, with perimeter tiles secured twice. Perimeter tiles sit along the verge and eaves, where wind has most effect.
The standard is guidance rather than regulation, so it is applied by judgment. A good roofer reads it alongside the tile maker's own instructions, which are often stricter than the minimum, and fixes to whichever asks for more.
What mechanical fixing means on a ridge
Mechanical fixing means something other than adhesion holds each tile down. On a ridge, that is usually one of a few kinds of hardware. A stainless clip can hook over the tile and screw into a ridge batten. A strap can run across the ridge tile and fix to the roof structure each side. A bracket can carry a dry-fix ridge system. What they share is that the tile stays in place when the mortar around it has cracked.
The mortar on a bedded ridge still closes the joints and fills the space beneath the tile. The mechanical fixing is the second line. If the mortar fails over the years, the clip or strap keeps the tile where it is until someone repairs the bed. That gives time and safety, since a ridge tile falling from the top of a roof is a hazard to anyone below.
Why the pull matters more than the push
Think of what a gale does to the highest tile on the roof. Wind passes over the slope and speeds up near the ridge, which lowers the pressure above the tile and tries to lift it. A bed of mortar resists being pushed down very well, and pulled up very poorly. A clip or screw does the opposite job, resisting the lift. Wienerberger makes the same point about field tiles: every single-lap tile must carry a minimum of one mechanical fixing, with the fixing plan drawn up per site from its location, its altitude and the wind it faces.
This is why fixing is not left to habit. It is matched to the roof it is on.
Bedded with fixings, or dry: both meet the idea
There are two routes to a ridge that satisfies the standard's approach. The first is a mortar bed with mechanical fixings added. The second is a dry-fix system, in which the fixings do all of the work and the mortar is replaced by a vented roll and clip hardware.
The dry route has its own standard. BS 8612:2018 is the dry-fix specification, covering ridge, hip and verge products for slating and tiling, and Marley treats it as the test those systems are measured against. A system made to it has been tested against a set of defined requirements, which gives a roofer and a homeowner something definite to ask for.
Choosing between them
Neither route is wrong. A bedded ridge keeps the traditional appearance and suits many older houses, so long as it is properly fixed behind. A dry ridge is quicker to fit in poor weather and gives a regular finish. Cost, looks and the roof's condition decide it, and we compare them in our guide to BS 8612 dry-fix and in the piece on ridge re-bedding.
Where we do re-bed a ridge, we fix the tiles mechanically as well, not as an optional extra. On a Channel-facing roof where a gale tests every detail, we do not see a sound reason to leave it out. If you are quoted for a re-bed that is mortar only, ask why.
Whichever route is chosen, the test of a finished ridge is simple: no tile should move when it is checked by hand at the final inspection.
Hips, verges and the rest of the roof edge
The same thinking applies beyond the ridge. A hip is the outward sloping corner where two roof planes meet, and hip tiles cap it just as ridge tiles cap the top. They face the same wind and carry the same risk, so the standard treats them in the same way, and our page on hip tile repairs covers the particular points of that detail.
A hip adds a further difficulty. Where a bedded hip tile sits on a sloping line, gravity pulls it down the slope as well as the wind pulling it up. A hip iron, a small metal bracket at the foot of the hip, can stop the bottom tile slipping. The hip tile at the top meets the ridge, where several tiles come together and need careful fixing.
Verges and perimeter tiles
Verge tiles run along the gable edge and are among the most exposed on the roof. Perimeter tiles, as Marley records, are fixed twice, which is why the edge of a roof is usually fixed more heavily than its middle. A verge pointed in mortar and nothing else is not the approach the standard has in mind. A dry verge, covered by BS 8612, solves it with caps and fixings, a topic in our guide to dry verge systems.
Some owners notice that their dry verge caps hum or rattle in a strong wind. That is generally a fitting issue, not a standards one, and our note on dry verge noise goes through what to check.
Coastal sites, airports and site-specific fixing
The wind a roof must resist is not the same in every place. Marley sets out the approach: BS EN 1991-1-4 gives the starting wind speed for the location, and further adjustments for surrounding ground, topography and the size of the building convert it into pressure on the roof. A hilltop house, a seafront flat and a sheltered cul-de-sac all come out differently, and the tile maker's fixing specification reflects that.
Pitch matters too: below 30 degrees, the windward slope can see strong suction, according to Marley. That covers many bungalow roofs and extensions along this coast, and it is one reason a low-pitched roof asks more of every fixing.
Near Shoreham airport
Roofs near airports can experience high local wind load forces from the air vortices that large aircraft create on take-off and landing, and these may be greater than the loads calculated to BS 5534. Marley says that if a site is within 6 km of an airport, you should contact its Technical Advisory Service for guidance on the fixing specification. Some addresses in Shoreham, Lancing and Sompting could be inside that radius. We do not name distances for particular streets. If yours might be, the survey notes record it and we suggest getting the maker's advice before the work is specified.
The tile maker's specification for your site is the right reference.
At the survey that comes down to three plain questions. How steep is the roof, how open is the site, and what does the maker's literature say for that tile? The answers decide the number and type of fixing, not habit or whatever clips happen to be on the van.
Old roofs, heritage buildings and what it means for your quote
Not every roof is a modern tiled one, and the standard recognises it. Marley observes that the A2:2018 amendment clarifies how far the standard reaches on heritage roofs, where its advice will not always fit, and suggests asking the local council and conservation specialists. A roof that is listed, or in a conservation area, may call for lime mortar, traditional fixings or a more sympathetic detail than a modern clip. Ask the council before the detail changes, and a listed building usually needs the council's view before any change.
For an ordinary house, the standard is a useful test of a quote. A sound ridge quote says how the tiles are held, not just how they are bedded. It names the fixing, say a clip or a strap, or the dry system and its maker. If it only says re-bed and point, ask what holds the tiles when the mortar cracks.
How we apply it
At the survey we press the ridge tiles, lift a few where we can, check the bed and battens under them, and take photographs. If the ridge needs work, our recommendation is the smallest job that holds, with the fixing method named. Our quote, one total price, comes after the survey and names the fixing method for the ridge, so you can see what holds the tiles down. For typical costs and the wider service, see our ridge tile repairs page.
