Pitched roofing in Bath, repaired and re-covered to match

Look at a tiled roof from the street and you see rows of tiles, each row slightly below the last. Those rows are courses. No mortar joins one tile to the next across the slope. The roof stays dry because every tile sits partly over the tiles beneath it, so water running down is always passed on to the next course and never gets a straight route to the timber.

The way tiles overlap depends on the type. Clay plain tiles are small, slightly curved and laid so that each course covers the course two rows below, a double lap. A plain tile roof therefore has two or three layers of tile over most of its area. Concrete interlocking tiles are larger and have grooves along their sides that lock into the neighbouring tile, so a single lap is enough and the roof goes on faster. Pantiles have an S-shaped profile, with one curve running under its neighbour and the other over it, and they rely on the shape to carry water down the channels.

How a tile is held on

Most tiles hang from a batten by a nib, a small lug on the back of the tile, and the nib does most of the holding. Nails or clips are added at intervals across the roof, and at every edge. When a tile slips, the usual story is a snapped nib, a nail that has rusted through or a batten that has softened with rot. Wind plays its part, but a sound tile on a sound batten is hard to shift. That is why we do not simply drop a new tile into the gap. We lift the tiles around it and look at what was holding the old one.

Cracked tiles have different causes. Water that soaks into a porous tile and freezes will split the surface in layers, and a tile that has been trodden on by someone with a ladder or a boot can carry a hairline crack for years before it opens. We replace cracked tiles individually where the neighbours are sound. If a whole slope is flaking, the better answer is usually to re-cover it.

Matching what is already there

The Freshford and Sharpstone conservation area appraisal says natural clay tiles are common there and that a significant number of buildings keep their Cotswold stone tiles. It adds that re-covering a roof there in concrete tiles harms the village scene. The same logic applies in Bath. A clay roof patched with concrete tiles looks wrong and behaves differently, because the two have different weights, sizes and fixings. We match the tile type first, then the colour and size, and use reclaimed tiles where new ones would stand out.

Our guide to clay, concrete, plain tile and pantile roofs compares the main coverings, and why tiles slip goes through the causes one at a time. If you have a tile on the path, the second page is the one to read first.

A plain slope is easy to cover. A hip and a valley are where two slopes meet, and both ask the roof to do more. A hip is the external angle, the ridge-like line that runs down the corner of a hipped roof. A valley is the internal angle, the channel where two slopes drain into each other. In a downpour the valley takes the run-off of two slopes and delivers it down one narrow line.

Hips are covered with hip tiles, which are bedded in mortar, fixed with a dry-fix system or both. Dry-fix means mechanical fittings, usually clips and screws, that hold the ridge and hip tiles without relying on mortar. Under BS 5534:2014, the tensile strength of mortar by itself is not relied upon for ridge and hip tiles, and bedded tiles and fittings are expected to carry mechanical fixings. BS 8612:2018 sets the test standard that dry-fix systems are measured against. On an older roof we often find hip tiles held by nothing but cement mortar that has cracked and let go, and a refix with proper fixings is the repair.

Valleys and what lines them

A valley can be lined with lead, with a GRP gutter or with a purpose-made tile. A lead valley is a sheet of lead dressed into the angle, and the tiles at each side are cut to follow it. Lead lasts well, but it can split where it has been thermally stressed or walked on, and the fixings can fail at the top edge. In a closed valley, the tiles meet in the middle and hide the lining. In an open valley, a strip of the lining stays visible. Both are common on older houses in the area.

Where a valley meets a wall, chimney or dormer cheek, the join is made with flashings and soaker pieces. A flashing is lead or similar metal strip that seals the join between the roof and a vertical surface. A soaker is a small folded sheet of metal tucked beneath the tiles beside a wall, so water is steered back onto the slope. Most valley leaks we see are at these junctions and not along the length of the valley itself.

We open up a leaking valley, look at the lining and the timber board beneath it, and repair or replace what has failed. If the board is rotten, it is replaced first, since new lead on a soft board will not last.

Figures: MyBuilder pricing guide for new roofs, 2026 edition

A hipped roof costs more than a gabled one because it has more cutting, more ridge and more angles to seal. Our page on hip or gable roofs sets out the differences, and the ridge, hip and verge repair service covers the tiles along the angles in more detail. For lined valleys, see lead roofing.

The verge is the sloping edge of the roof beside a gable wall, where the tiles stop and the masonry carries on. It is the place the wind gets under first. Air pushed up the face of the gable gets under the edge of the roof and tries to lift it, so verge tiles need to be held down properly.

On a traditional roof the verge is finished with the tiles overhanging the gable wall by a short distance, bedded in mortar on a layer of undercloak. The undercloak is a course of tile, slate or fibre-cement board laid under the verge tiles to give the mortar something to sit on and to carry water back onto the roof. In older work the verge mortar was often a lime mix that could flex a little. On later roofs it is usually cement, which is stiffer and cracks more easily as the roof and wall move at different rates.

Mortar, dry-fix and mechanical fixings

BS 5534:2014 expects mechanical fixing of bedded verge tiles as well as ridge and hip tiles, because mortar alone cannot be relied on to resist the wind. Where the old verge is cracked, we can re-bed it with mortar and add mechanical fixings, or replace it with a dry-fix verge system that is clipped and screwed down. BS 8612:2018 is the standard that dry verge systems are tested to. Dry-fix needs no mortar, so it is faster to fit and does not crack. It is a visible change, though, and a mortar-bedded verge may be the better match for a listed house or one inside a conservation area.

We look at the verge from the ground first. Cracks in the mortar, a gap between the tile and the wall and tiles sitting at a slightly different angle all point to movement. From the roof we check whether the undercloak is sound and whether the barge board or the gable-end timbers are rotten. A verge that is loose is dangerous, because a section can lift in a gale and fall into the street.

The decision between re-bedding and dry-fix comes down to the age of the house, the condition of the undercloak and what the verge looked like originally. We explain the options after the survey, with photographs of the verge in question.

Our ridge, hip and verge repairs page covers the fixing options in more detail, and the roof pitch guides help when a change of covering is on the table. If you are choosing a tile for a new gable, read roof pitch and tile choice first.