Do roof tiles need clips and nails?

BS 5534 is the British Standard code of practice for slating and tiling. It sets out how tiles should be fixed so that wind cannot lift them. The detail depends on the tile, the roof pitch and how exposed the site is, and the tile maker's own data sheet adds to it, so the right pattern for one roof is not the right pattern for the next.

In practice the standard distinguishes the field of the roof, where most tiles sit, from the edges, where wind pressures are higher. At the eaves, verges and ridge, tiles are held down more firmly than in the middle. Each tile usually hangs on a batten by its nib, and a nail, a clip or both stop it lifting. We follow the manufacturer's fixing specification for the covering on your roof and note what we find during the survey.

The ridge is the top line of the roof, hips are the sloping external angles, and verges are the sloping edges at the ends of the roof. They take the greatest wind pressure, and they used to be held by mortar alone.

Marley explains that the 2014 revision of BS 5534 ended any reliance on the pull-out strength of mortar. Since then bedded tiles and fittings have carried mechanical fixings too. A dry-fix system, which replaces the mortar with fixed components, is tested to BS 8612, and untested products cannot be used to demonstrate compliance. Mortar bedding is not outlawed; it simply has to be accompanied by a mechanical fixing. Cost guides give dry ridge at £40 to £60 per metre in MyBuilder's guide, and Checkatrade's repair guide shows £50 to £70 per metre for dry ridge and £70 to £100 for dry hip, before VAT.

A roof laid before 2014, or long before, was built to the practice of its day. Tiles may be nailed every few courses, with the rest hooked over the batten and held by their own weight. Original nails rust, clips loosen and mortar crumbles, so a ridge that was sound when laid can now be held by very little.

On a survey we start with the fixings. A roof can look neat and still be under-fixed, and the first hint is often a gale lifting a few tiles at the edge. It is a different matter from one failed fixing; our answer on slipped roof tiles explains how a tile that has moved is refixed, while this page explains the standard a roof is held to.

A nail goes through the tile into the batten. A clip holds the tail of the tile and is nailed to the batten, which helps where a tile has no nail hole or a perimeter tile needs extra restraint. The choice between them, and the number needed, comes from the tile maker's guidance and BS 5534.

Corrosion is the everyday enemy. A nail that has rusted through at the shank lets a tile slide with no warning from outside, so replacement fixings should be corrosion resistant. If tiles are slipping in a line, rotten timber may be the real cause, and rotten roof battens shows what to look for. A fixing that grips rotten wood holds nothing, and a survey with photographs tells the two apart.

Cut tiles round pipes, vents and abutments sit outside the standard pattern, so their fixings are checked one by one.

Dormer cheeks, tile vents and any tile cut round a pipe all need their fixings checked, since cut tiles sit away from the usual pattern. You may want to read roof tile vents and dormers and permitted development if you are planning changes to a roof.

Bringing an under-fixed roof up to the standard can mean refixing the ridge and verges with a dry-fix system, adding clips, or relaying a slope. A written quote follows the survey and takes in scaffold, materials, labour and waste. A workmanship guarantee of 10 years, in writing, covers what we fit. Other tiled-roof topics sit under pitched roofing.

Wind pulls hardest at a roof's edges. The eaves, the verges and the ridge see the biggest suction, which is why perimeter tiles are fixed more heavily than those in the middle of a slope. A tile at the verge may be nailed and clipped, where its neighbour in the field is nailed only.

Site exposure counts as well. A house on an open hillside, or standing taller than its neighbours, sees stronger gusts than one tucked into a terrace, and the standard takes the situation of the building into account along with pitch and tile type. We look at where your house sits when we read the roof.

On a repair, we match what is there and raise it to the standard where we touch it. If we lift a verge to deal with a leak, it goes back with proper fixings, not with the mortar alone that held it before. If the remainder of the roof is under-fixed, the survey records that and we tell you, so you can accept or decline the extra work. You will also see photographs of the fixings we found, close up, and the tile type is named in the quote so that the right clips are ordered.