The short answer
A hip iron is a metal bracket fixed to the roof at the bottom of a hip, where it supports the lowest hip tile and stops the whole row sliding towards the gutter. Hip tiles sit on a steep slope and a mortar bed cannot be trusted to hold them by itself, so the iron carries part of their weight. If it rusts, bends or is missing, the hip tiles can slip and the hip needs refixing.
Where a hip iron sits and what it does
Picture a hipped bungalow, or the end of a semi with no gable. The sloping line at each outward corner, where two roof planes meet and fall from the ridge to the eaves, is the hip. Hip tiles cover that line, just as ridge tiles cover the ridge, and they lie on a steep slope that gravity constantly tries to pull downhill.
The hip iron is a flat strip or small bracket, bent to a hook or a shelf, screwed to the rafter or hip timber at the lowest point. The first hip tile rests on it, and every tile above that rests against its neighbour below. Remove the support at the bottom and the whole row loses its anchor. On older roofs the iron is often hidden under a bed of mortar that gives the foot of the hip a neat finish, which is why many owners have never noticed one.
Why mortar alone is not enough
Until the 2014 revision of BS 5534, a bed of mortar was commonly accepted as the sole fixing for hip tiles, and the iron was seen as a back-up. After that revision, a screw, clip or strap is expected beside the mortar. Hip tiles take the load of their own weight down a slope, and mortar is weak in tension, so a bed that cracks or loses its grip leaves the tiles hanging on whatever else is holding them.
On modern dry hip systems the lowest unit is clipped or screwed to a purpose-made bracket, which does the job of the old iron in a tested form, as described in BS 8612:2018. For a traditional mortar hip, the iron remains the key mechanical fixing at the bottom. Our page on the types of ridge tiles shows how hip tiles differ in shape and why some need extra support.
How a hip iron fails
At the lowest corner, water runs off the tiles and sits against the metal, so irons are among the first fittings on the roof to suffer. The usual faults are these.
- Corrosion. A plain steel iron rusts, swells and breaks its mortar bed from inside. A galvanised or stainless one lasts far longer.
- Loose fixings. The screws or nails that hold the iron go rusty or pull out of an old timber.
- Bending. A tile that slips can bend the iron, which then no longer supports it.
- Never fitted. Some older roofs were built without one, relying on mortar, and the hip has crept ever since.
The signs from the ground are a hip tile at the bottom that has dropped, a gap or crack at the foot of the hip, a rust stain running down the tiles below, or a lower tile that has tilted outwards. A hip that looks as if it is leaning, or a line of mortar fallen on the lower slope, deserves a closer look.
How a missing or failed iron is replaced
Replacement means lifting the lowest hip tiles, removing the old bed and the old bracket, and checking the timber beneath. If the hip rafter is sound, a new galvanised or stainless iron is fixed with screws long enough to bite properly into it. The tiles go back on a fresh bed, with a mechanical fixing alongside, in step with the standard. If the timber is soft, it is cut back to sound wood, or a new piece is fitted, before the iron is fixed.
Where a roof has a dry hip system, the same job is done with the maker's own start bracket, taken from the range the other units belong to. It is not a place for improvisation: a bracket that does not match the system will not carry the load the way a tested one does.
We recommend replacing the iron at the same time as any other work on the hip, because the tiles have to be lifted anyway and the iron costs little next to the access needed to reach it. Where the hip meets a ridge that is ventilated, the two need to work together, and our page on ventilated ridges explains how air gets out at the top without letting rain in.
It also pays to ask what the tiles above the iron are sitting on. A hip with cracked or hollow bedding along its length is often one where the iron has already given way, and fixing only the bottom leaves the rest to fail in turn. A survey looks at the whole run, from the foot to the junction at the ridge.
Why hip tiles are not a DIY job
A hip is at the very edge of a roof, normally above a lower storey, and tiles dislodged during a repair fall straight onto the ground. The fixings need an accurate fit to the batten or rafter, and the setting out of the tiles along the hip has to line up with the ridge at the top. Our guide to fixing ridge tiles yourself explains the risks, and the same applies with extra force here.
The verge is the next-closest edge, and a worn verge undercloak often shows up on the same visit. For the whole picture of these parts, see ridge and verge dry-fix.
If a hip tile has dropped or an iron is visible and rusting, send a photograph from the ground. Expect photographs of your own hip and a quote in writing, sized to the job. Our labour is guaranteed for ten years on paper, and the debris is taken away.