The short answer
Bonnet hip tiles are curved clay tiles, rounded like a bonnet, that cover the hip of a roof where two sloping planes meet at an outward corner. Each tile has a tapering shape so the row steps neatly up the hip. They are found on traditional clay tile roofs, and repair means matching the profile and colour, re-bedding them securely and renewing any lead or mortar beneath.
What the name means and what the tile looks like
A hip is the sloping line on a roof where two planes meet at an outward corner, that runs down from the ridge towards the gutter line. Something has to cover that join, and on a clay tile roof the traditional answer is the bonnet hip tile.
The tile is shaped as a shallow curve, a little like the brim of a bonnet, with one end rounded and the other cut to sit under the tile above. Laid in a row, the tiles overlap down the hip like scales and give a softly stepped line. This is quite different from a plain angled ridge tile, which has a flat-sided profile with a hard peak.
The rounded end is the feature people recognise. Seen from the garden or the street, a hip finished in bonnet tiles has a hand-made, slightly irregular edge that suits an older clay roof and is part of why the detail has lasted.
Where they are found
Bonnet hips go with plain clay tiles, the small rectangular tiles with a gentle camber that are common on older houses. They are a feature of traditional hipped roofs, where a hip tile is chosen to blend with the covering around it, in the same clay and the same range of colours.
They are not unique to any one type of house, and you will see them on cottages, villas, farmhouses and outbuildings with a hipped end. The detail is more visible on a roof where the hips can be seen from the road.
We cannot say how many local roofs carry them, because we have no sourced figure, so we say only that they are a recognised traditional finish. If you want to know whether your own roof has them, the hips are the place to look. A row of rounded, overlapping tiles running down the corner is a bonnet hip. Our guide to loose ridge tiles deals with the matching problem along the top of the roof.
How a bonnet hip is built
Each tile is laid in a bed of mortar along the hip, beginning low at the eaves and building upward to the ridge. A hip iron is often fixed at the foot of the hip. It is a small metal support fixed at the foot of the hip to hold the lowest tile in place, because tiles bedded on a slope are always trying to slide down it.
Beneath the tiles, the hip is weathered in one of two ways. The roof tiles on either side may be cut and angled to meet along the hip line, or the join may be lined with lead. The lead channel, called a soaker or a hip lead, carries any water that gets past the tiles on to the roof below. When the bonnet tiles are lifted for repair, the condition of that lining gets looked at early.
BS 5534:2014 expects bedded hip tiles to be mechanically fixed, because mortar alone cannot be relied upon. A traditional hip may predate that practice, so a repair is a chance to add a proper fixing without changing how the hip looks.
What goes wrong
The usual faults are plain. The bed of mortar cracks and drops out, just as it does on a ridge. Tiles loosen and slip down the hip. Frost flakes the face off a tile that has been soaking water. Sometimes a single tile cracks where it was hit by a branch or a fall of other tiles.
The hips also take more weather than people expect. A hip faces the wind from two directions at once, and the tiles on a ridge or hip sit highest and most exposed on the roof. Birds and moss thrive in the gaps once the mortar goes, and moisture gets in behind.
Look for a gap or a line of daylight along the hip, a tile that has dropped below its neighbours, or mortar on the ground near the wall. Stains on the ceiling below the corner of the roof, after rain, can point to a failed hip lining. Our page on lime mortar for ridges explains why the choice of mortar matters on older work.
Repairing bonnet hips properly
Repair starts with lifting the tiles from the damaged length and checking what is underneath. Sound tiles are cleaned and kept for reuse, a point covered in our answer on a dry verge on an old house as well. A cracked or flaked tile is replaced with one that matches, and since bonnet tiles are made in particular shapes and clays, a reclaimed tile is often the closest match for an old roof.
The lead or the cut-in tiles beneath are checked and renewed if they are worn. A new bed of mortar is laid, a lime-based one where the building suggests it, and the tiles are set from the bottom up with the hip iron secured at the foot. Mechanical fixings go in as the tiles are laid.
Mixing in a dry-fix hip system is possible, but on a roof with bonnet tiles the system must suit the rounded profile, and it may change the look of the roof. Ask B&NES planning first if the house is listed or stands within a conservation area, since the detail would change.
Our survey costs nothing and includes pictures of the hips on your roof, after which the fixed price comes in writing. A well repaired hip shows bonnets sitting in a straight, even line, each fully bedded and held with a nail, with the bottom one supported by the hip iron. The main page on ridge and verge repairs page.
