Quotes mention BS 5534 without saying what it asks for. This guide covers the standard's status, the mortar change, how exposure sets the fixings and what to look for in a written specification.
Most of the work in a tiled roof is invisible once it is finished. The tiles are what you see; the nails, clips, battens and ridge fixings are what keep them there in a gale. A British Standard governs that hidden part: BS 5534, the code of practice that covers how pitched roofs are slated and tiled. BSI lists BS 5534:2014+A2:2018 as the edition now in force.
You may meet the number in a quote, a manufacturer's data sheet or a surveyor's report, usually as a single line saying the work will be done "to BS 5534". That line is worth understanding, because it can mean a precise calculation or it can mean very little. The standard is a code of practice, not a statute, so whether it is followed is a matter of the specification you agree, not of law.
This guide explains what the code is, what changed after 2015, how a fixing specification is worked out for a particular roof, and how to read a quote that refers to it. It sits alongside our work on pitched roofing, where the fixings matter on every re-roof and on any repair that disturbs the covering.
What BS 5534 is, and what it is not
BS 5534:2014+A2:2018 is the edition BSI lists as current. It sets out how coverings, battens, underlays and fixings should be selected and installed so that the roof stays on in wind and sheds water as designed. The title and status are listed on the BSI knowledge site, and that is the edition a specification should name.
The standard is not the law. Marley, one of the tile makers, says plainly that "Installing to BS 5534 isn't required by law". That does not make it optional in practice. Building Regulations carry their own duty: Approved Document C expects every tile and slate on a roof to be secured in a way that suits it. A roofer who follows BS 5534 has a recognised way of showing that duty is met, and a roofer who does not has to show another.
It helps to keep the roles apart:
- BS 5534 is the code of practice: a method and a set of calculations.
- The tile or slate maker's data sheet gives the fixing for each product, including the minimum pitch.
- Building Regulations set the outcome: the covering must be fixed in an appropriate manner.
- Your written specification joins the three, for your roof, on your site.
In practice, "to BS 5534" in a quote is only as useful as the detail behind it. Ask which edition, which tile or slate, and what fixing is proposed for the field of the roof, the eaves, the verges and the ridge. A specification that answers those four points is a specification. A bare reference is not.
The 2015 change: mortar alone is not enough
For generations, ridge and hip tiles were bedded on mortar and left to it. Mortar is strong in compression but weak when it is pulled, and a ridge tile in a high wind is being pulled. Marley records that the 2015 amendments to BS 5534 ended any reliance on mortar as the sole means of holding the covering down. Marley adds that the reason is the limited strength of mortar when pulled.
Notice what that says and what it does not. It does not ban mortar. A mortar bed is still used to seat and seal ridge and hip tiles, and on many old roofs it is part of how the roof looks. What changed is that mortar on its own no longer counts as the fixing. A mechanical fixing, such as a clip, a nail or a screw, has to work alongside it, or the whole ridge is built as a dry-fix system instead.
Systems that dry-fix the ridge, hips and verges have their own standard, BS 8612:2018, which BSI lists as current. In a dry-fix system the capping is held by mechanical fixings and the joints are closed by a flexible or ventilated component, so there is no reliance on a mortar bed to carry the load.
If a quote says the ridge will be "re-bedded", it is fair to ask whether that includes mechanical fixing, and whether the finished ridge meets BS 5534 as amended. A ridge that rocks under a hand, or shows open joints, has usually lost its bedding or its fixing, so it is worth having looked at before the next stormy spell.
Why fixings change from one roof to the next
Two houses with the same tiles can need different fixings. The reason is exposure. Cupa, a slate maker, rates tall buildings as more exposed, as it does sites on slopes, hills or the coast. Marley adds that BS 5534 carries formulas for wind uplift, from which the fixing specification is derived. The outcome is a calculation, not a rule of thumb, and it is run for the exposure of the site in question.
That is why a fixing is never named before the roof has been seen. Met Office averages for Manston, covering 1991 to 2020, give a mean wind of 9.86 knots at 10 m and 11.21 knots for January. They are background from one station, not a design value, and they do not replace the calculation.
The things that move a specification include:
- how exposed the site is, which a tall house on a hill and a low terrace in a sheltered street answer differently;
- the height of the building and the position on the roof, since eaves, verges and ridges see more uplift than the field;
- the tile or slate chosen, because each has its own fixing requirements;
- the pitch of the slope, which also governs the lap and the underlay.
On a re-roof the specification is written once, for the whole roof. On a repair it covers the area being worked on, but the same logic applies: a replacement tile should be fixed in the way the data sheet and the standard call for, not simply pushed into the gap and left to hang.
Pitch, lap and what the data sheet limits
A fixing specification starts from the pitch. Every tile and slate has a minimum pitch below which it is not meant to be used, because water can be driven back up under the laps in wind. The maker's data sheet publishes the minimum, which narrows what can be chosen for a given slope.
| Covering | Minimum pitch |
|---|---|
| Marley clay, Canterbury (a tile name) | 40° |
| Marley concrete, Plain | 35° |
| Marley concrete, Anglia | 25° |
| Marley concrete, Mendip | 15° |
| Natural slate (500 mm slate, 115 mm lap) | 20° |
The first four rows come from Marley's table and the last from Cupa, who say BS 5534 indicates a minimum roof pitch of 20 degrees for natural slate where the exposure is moderate. Always check the data sheet for the exact product. "Canterbury" here is the name of a Marley clay tile, not a place.
Fixing method also changes with pitch. Cupa advises against hook fixings on pitches below 25°, so a low-angled back addition or dormer can call for a different fixing from the main slope, even with the same slate.
The headlap, which is how far each course overlaps the one below, and the gauge, which is the batten spacing, are part of the same calculation. They decide how far water has to travel to get under the covering. Before any quote refers to a covering, the pitch of each slope should have been measured on site, since a roof line that looks consistent from the street can change at an extension or a porch.
Re-roofing, repairs and BS 5534:2014+A2:2018
The 2018 amendment widened the standard's reach. Marley says A2:2018 brought ordinary re-roofing, repairs included, inside the standard's scope. So a repair is not outside the code: replacing slipped tiles, or re-fixing a run along the verge, is the kind of work the standard now speaks to.
For the homeowner this has a practical side. A re-roof starts with the stripping of the old covering, which shows the battens, the underlay and the rafters. The specification then sets what goes back on:
- Battens sized and spaced for the covering and the pitch.
- Underlay chosen for the roof's ventilation, noting that BS 5250:2021 is the current code for moisture in buildings.
- Tiles or slates fixed as the calculation requires, field, eaves, verge and ridge each treated on its own terms.
- Ridge and hips either dry-fixed to BS 8612:2018 or mortar-bedded with mechanical fixing alongside.
- Verges closed in a way that does not rely on mortar alone.
Re-roofing also raises a separate question: whether Building Regulations approval is needed. Under the Planning Portal's test, a job normally stays outside building control when under 25 per cent of the building envelope and under 50 per cent of the roof is touched. A new covering 15 per cent or more heavier needs approval. Because a whole re-roof touches every slope, the council's building control team is asked first.
Our guide to a slate re-roof, stage by stage shows where the fixing work sits in the sequence.
Asking for fixings in a written specification
When a quote says the work follows BS 5534, the questions below turn the reference into something you can check. They are not a trap; any tradesperson who has done the calculation can answer them in a minute.
- Which edition of the standard is being used? The current one is BS 5534:2014+A2:2018.
- What tile or slate is it, and what is its minimum pitch against the measured pitch of the slope?
- What fixing goes in the field, at the eaves and at the verges?
- Is the ridge dry-fixed to BS 8612:2018, or mortar-bedded with mechanical fixing alongside?
- What exposure was the calculation based on, and who worked it out?
On cost, the fixings sit inside the one written total, so the useful comparison is whether each quote describes the same fixing. For published guides, Which? gives £80 to £300 for putting in a new ridge tile, ex VAT (Nov 2025), and MyJobQuote puts a dry verge system between £500 and £2,000 (08/10/26). Both are typical UK ranges, and Which? adds that South East prices tend to sit higher, which takes in Kent.
Citizens Advice recommends at least 3 written quotes from different traders before you choose. When you do, compare what each says about fixings as well as the price, since a cheaper quote may simply assume less.
If you have a specific ridge in mind, our page on whether roof tiles need clips covers the question from the tile's side.
