The short answer
No. No law says a verge must be dry fixed, and mortar is not banned. What exists is a code of practice, BS 5534, which looks for a mechanical fixing on every bedded tile, and a test specification, BS 8612, for dry systems. Both are guidance that roofers, surveyors and warranty providers work to, not statute, while Building Regulations touch re-roofing in other ways.
Dry verge is a recommended method, not a legal duty. Here is what the standards say, what the Building Regulations cover, and who decides on your roof.
What the law does and does not say
Look at the side wall of a gable-ended house and you will see the verge, the sloped edge where the roof stops. For decades it was finished with a bed of mortar under the last row of tiles. A dry verge swaps the mortar for caps or lengths held with screws or clips. Nothing in the Building Regulations or any Act says you must fit one, and nothing says you cannot use mortar.
Marley says plainly that installing to BS 5534 is not required by law. That standard is BSI's code for slating and tiling, listed as current in its 2014 edition with the 2018 amendment. BSI also cautions that parts of it could be wrong for an older roof being re-tiled, particularly where old hand-made or second-hand tiles are involved. So there is no blanket rule that every verge must be redone as dry.
What has shifted is practice. Marley explains that the 2014 revision of BS 5534 drew a line under leaving ridge and hip tiles to rely on mortar alone. Anything bedded should now also be held by a clip, screw or strap. A roofer working now will normally follow that, which is why a bare mortar verge with no fixings is rarely fitted new.
Where BS 5534 and BS 8612 come in
BS 5534 covers how tiles and slates are held down, verges included. BS 8612 is a separate document, the specification used to test dry systems for the verge, the hips and the ridge, and BSI lists it as current from January 2018. A system tested to it has passed set checks, which gives you something to compare when you choose.
Because these are standards and not statutes, breaking them carries no fine. They matter in other ways. If a roof fails in a storm and the work is looked at afterwards, a surveyor, insurer or warranty provider may ask whether it followed the recognised method. A new-build roof may also come with a builder's specification that requires it. When you are given a quote, it is fair to ask which standard the work follows and whether the system has test evidence.
For the detail of how a properly fixed edge looks, see our guide to BS 5534 ridge and verge fixing, which goes through the fixing recommendations step by step.
What the Building Regulations do cover
Building Regulations do not single out the verge, but they can reach the roof work around it. Its national test for a normal re-roof asks whether under 25 per cent of the building envelope and under 50 per cent of the roof is involved; on top of that, a covering that adds 15 per cent or more in weight, or reacts differently to fire, brings approval into the picture.
A small verge repair sits well inside those limits, because a verge is a narrow strip of the whole roof. A full re-roof is a different case, and a mid-size repair near a chimney or valley may be too, and the Planning Portal wants weight checked with an engineer or surveyor before any big job starts, since a heavier covering can load the rafters. Your building control body, whether the council or a registered private approver, can tell you if your job needs an application.
In Crawley, the council's own building control team is the place to ring. Elsewhere, ask the local council. On larger jobs we look into this during the survey and report back with photos.
Mortar, listed buildings and what to do next
Mortar is still a valid finish in the right place. Some roofs, particularly older ones with reclaimed tiles or traditional detailing, suit a bedded verge, and on a listed building the look may be a condition of consent. Where the roof is old, BS 5534 itself says its advice may not fit, so the choice is a matter of judgement for the building, not a rule.
Should the house be listed, or inside a conservation area, ask the council's planning team before the look of the edge changes. Like-for-like repair of a listed roof may not need consent, but changing the finish might.
If you are weighing up the choice for your own roof, our answer on whether ridge tiles need mortar covers the same question for the crest, and the dry ridge and dry verge page sets out the options. Send a photo of the end wall with the age of the house, and our reply will say what we expect to meet along that edge. Keep any survey report that mentions the verge too, since it shows what a valuer or buyer has already spotted.
More on this in Dry Ridge & Dry Verge Systems in Crawley
Two more questions on verge rules
Does my insurer require a dry verge?
Read your policy wording or ask the insurer directly, because terms differ from one policy to the next. A storm claim is judged on the policy and the circumstances, and an insurer may look at how the work was done. Keep the paperwork for any roof repair, including the system used and photos taken during the job.
Can I be made to replace a mortar verge?
A neighbour, buyer or surveyor can point out a failing verge, but nothing in law forces you to replace a sound mortar one. A mortgage valuation or survey may flag loose edge mortar as a repair. In that case, get a roofer's opinion and a written price, and decide on the system together.