Chapter one
Steep plain-tile slopes, hips and half-hips
Petworth's tiled slopes are steep by design, and every hip and half-hip on them is another line where water can get in.
Clay plain tiles are small and flat, and they lap over one another in rows, every tile hanging by two projecting nibs from a batten (a narrow timber strip). The Petworth conservation area appraisal says steep clay plain-tile roofs predominate in the town, varied by gables, hips and half-hips. Steepness helps water run off quickly, but it also means more roof to inspect and a harder climb. Half-hips make the end of a roof more complicated: the gable's peak is trimmed back, so the end gains a short sloping facet and two extra hip lines that a plain gable never has. Each hip, ridge and valley (where two slopes fold together inwards) is a place where tiles are cut to fit and where water can find a way in.
At a glance
- Plain tiles hang from battens by two nibs
- Marley's clay plain tiles need 30 to 40 degrees
- Hips and ridges now get mechanical fixings
1.1 Pitch decides which tile belongs
Marley publishes minimum pitches for its clay plain tiles, from 30 degrees for the Hawkins and the Acme Single Camber up to 40 degrees for the Canterbury. A plain-tile roof is meant to be steep, and it should stay that way when it is re-covered. Some Petworth roofs may carry older hand-made peg tiles, and, in the Building Conservation Directory's view, the 60 years often given as clay's lifespan cannot be relied on for historic peg-tile roofs. For that reason a roof is judged here on what the survey finds on the day: tiles with cracked or flaking faces, nibs that have snapped, and battens that have gone soft. A tile that looks fine from the street can be hanging by a single nib.
1.2 Hips, half-hips and what holds them
Our first look goes to the hips and ridge. BS 5534 was revised in 2014 so that a ridge or hip tile does not depend on a mortar bed alone but is fixed mechanically too, so older hips that rely on mortar alone are often the first to loosen. At the foot of each hip sits a hip iron, the curved metal strap that stops the bottom tile sliding, and these rust. From inside the loft we look for daylight at the hips, damp on the rafters and soft battens. Because stains show away from the fault, we follow the water back before quoting, and pictures taken on your own roof go with the written quote. Our ridge tile repairs page covers the fixing choices, and pitched roofing deals with tiled slopes more widely.
Plain-tile facts for a Petworth slope
- Hawkins, Acme Single Camber
- 30 degrees minimum pitch (Marley)
- Ashdowne
- 35 degrees minimum pitch (Marley)
- Canterbury
- 40 degrees minimum pitch (Marley)
- New clay tile life
- Minimum of 60 years (Marley)
- Fixings on hip and ridge tiles
- Mechanical fixing as well as mortar, since the 2014 revision of BS 5534
Source: Marley minimum pitch and life expectancy pages; Building Conservation Directory; fetched October 2026
