BS 5534 and stone
Does BS 5534 apply to an old stone roof?
The short answer
Only partly. BS 5534 is the code BSI publishes for slating and tiling, and BSI itself warns that it may be a poor fit when some old roofs are re-covered, especially ones built of traditional or salvaged materials. A Horsham stone roof is exactly that case. The code is a guide for judgement rather than a rule of law, so the fixings are settled slope by slope at the survey.
How a modern fixing standard meets thick, hand-sorted stone, and what that means for the pegs, ridge and verges on an old roof.
What the standard is, and what it is not
BS 5534 is the code of practice that sets out how slates and tiles should be fixed so they stay put in the wind. The current edition is BS 5534:2014+A2:2018, published by BSI in February 2018. It deals with battens, nails, clips, headlaps and the fixing of ridges, hips and verges. Most of its thinking is written around machine-made tiles and quarried slate that come in regular sizes with a manufacturer's data sheet.
It is a code of practice, not an Act of Parliament. Marley, a tile maker, states that installing to BS 5534 is not required by law. In everyday work it serves as the yardstick for a new covering, the benchmark a building control officer or a surveyor may measure a roof against. So the useful answer to the question has two halves. The standard does not bind a repair to old stone. Its thinking still shapes what a careful roofer does on the ridge, the hips and the edges.
Why old stone sits awkwardly in the code
BSI flags the problem itself. Its own summary admits that the advice may not fit a re-cover of certain old roofs, above all where the materials are traditional or salvaged. That caveat describes a stone roof very well, and it is the reason a stone roof cannot simply be checked against every clause of the code. Whoever works on it has to understand why each requirement exists before deciding whether it fits.
Consider the material. A stone slab is thick, uneven and heavy, split by hand from the sandstone of the Weald, and no two are the same size. Traditionally each hangs on an oak peg from a batten, set in courses that get smaller as they rise. A standard written for uniform tiles cannot just be laid over that. Drilling a slab afresh to take a modern clip can split it, and the loads on a stone covering are a different order from the loads a clip is tested for. Our page on the weight of a Horsham stone roof explains what the timbers carry.
Where the standard does shape stone work
The idea underneath BS 5534 is simple. Nothing on the roof should depend on gravity, friction or mortar alone to survive a gale. That principle travels well. Since the 2014 revision, the code expects a mechanical fixing under ridge and hip tiles, not mortar by itself. On a stone roof we take the same view along the crest, down the corners and along the edge that closes the roof off above a gable wall, called the verge. Each gets a fixing that does not rely on the bedding staying sound.
What the fixing looks like varies with the roof. It might be a stainless steel fixing driven into a sound rafter or wall plate and hidden under a ridge piece bedded in lime. It might be a lead strap. What we will not do is leave an exposed ridge held up by nothing but old mortar. Our answer on the ridge for a Horsham stone roof covers the choices.
Settling the fixings at the survey
Since the code leaves space for judgement, the decisions are made when we have looked at your roof, and they go into the written quote. We examine batten sizes and spacing, check how each course is held, and see whether the pegs are sound or whether a slab has started to slide. Pictures from the roof itself come with the quote, so you can follow every point without climbing a ladder.
A repair of a few slabs keeps the existing method, with a failed fixing renewed in the same way. Our answer on oak pegs on a stone roof explains the thinking. A full re-lay is the stage where the verges and ridge are looked at hardest, because those edges take the worst of a gale. The price is one total figure that follows the survey, so what is fixed, and how, is agreed before anyone climbs onto the roof. If anything unexpected turns up once a slope is open, we stop and tell you before carrying on.
Listed roofs, building control and who to ask
On a listed building the method of fixing forms part of the roof's character, and changing it may need consent. Minor like-for-like repair in the same stone and the same manner is a different matter from altering how the roof is held. Our guide to like-for-like consent shows where the line sits, and your council's conservation officer can confirm it for your house.
Where a re-lay counts as work that has to be notified to building control, we explain that at the survey and deal with your building control body for you. A registered building control approver or the council can tell you whether your job needs notifying. Whichever route applies, the standard acts as a reference point, and the judgement of a roofer who knows old stone is what carries the day. Ask anyone quoting for the work how they mean to secure the crest, the corners and the gable edges, and why, because the answer tells you whether they have thought about the roof or only about the price. For anything else on these roofs, start at our Horsham stone roofing page.
Related questions
Fixing a stone roof
Will a new ridge on my stone roof be fixed as well as bedded?
In nearly every case, yes. After the 2014 revision of BS 5534, mortar is no longer left to do the holding by itself, so a mechanical fixing goes in alongside the bedding. On stone, the type of fixing is chosen to suit the old work and set out in the quote.
Can a surveyor ask how my stone roof is fixed?
A buyer's surveyor may well ask. We record the method used on each slope, with photographs, so you hold a clear note of how the stone is held and what was renewed. It saves guesswork if the house is sold, and it helps whoever looks at the roof next.