When people ask about types of roof they usually mean the outline, the shape you can see from the street. A roofer sees two layers. There is the form, such as gable, hip or flat, and there is the structure underneath: the rafters, purlins, trusses or joists that carry the weight and hold that form up. The two matter together. The shape decides where water runs and where the weak junctions fall, while the timber frame decides what can safely be cut, loaded or converted. This guide covers both, using the roofs we meet most often around Basingstoke.
The basic shapes of pitched roofs
A pitched roof is any roof with sloping planes, and nearly all British houses have one. The names describe how those planes meet.
A gable roof has two slopes that meet at a central ridge, with a triangular wall (the gable) at each end. It is the commonest form on semis and terraces, and its simplicity is a virtue: few junctions, easy drainage and straightforward repairs. At the gable ends the edge of the roof is finished with a verge, where the tiles run past the wall and are sealed with mortar or, increasingly, dry-fix trims.
A hipped roof slopes on all four sides. The sloping edges where two planes meet at an outward angle are the hips, and each one needs its own capping tiles, usually fixed with mortar and mechanical clips. A hipped roof sheds wind better than a gable, which is why it appears on detached houses in exposed spots, but it has more tile cuts and more ridge-and-hip work to maintain. A half-hip (sometimes called a jerkinhead) clips the top of the gable end with a small hip, and is common on 1930s houses.
A mono-pitch roof, also called a lean-to or single-slope roof, falls in one direction. It shows up on side extensions, outbuildings and some modern designs. The high edge butts against a wall, which means a flashing that has to be right.
A mansard roof has two slopes on each side, the lower one steep and the upper one shallow, which creates space for rooms inside the roof. It is a feature of some Victorian and Georgian town buildings and of modern loft conversions that borrow the idea. A mansard has many corners and a lot of flat or near-flat upper surface, so it carries both pitched and flat-roof detailing.
Valleys, dormers and the roofs that combine shapes
Few houses have a single simple shape. Where two pitched roofs meet at an inward angle you get a valley, a channel lined in lead, GRP or tile that carries the water of both slopes and so takes a lot of flow. A dormer is a small structure that projects from the slope to carry a vertical window. Its own roof may be pitched, hipped or flat, and its cheeks (the side walls) are often clad in tile or lead. Our page on the types of roof valley goes into how the different valley forms are built.
The more shapes a roof combines, the more junctions it has, and junctions are where leaks start. A plain gable roof can go decades with little attention. A complex roof with hips, valleys and a dormer needs more frequent checks at each of those details.
Flat and low-pitch roofs
A flat roof is not truly flat. It has a gentle fall, normally set by tapered timber or insulation, to push water to an outlet or gutter. In practice a flat roof is any roof below about 10 degrees, and they are found on rear extensions, garages, porches and some commercial buildings. The covering is a continuous membrane rather than overlapping tiles: EPDM rubber, GRP fibreglass, bitumen felt, asphalt or lead.
The type of flat roof depends on where the insulation sits. In a warm roof the insulation is above the deck, which keeps the timber warm and dry. In a cold roof it sits between the joists, with a ventilated void above it. Our warm roof versus cold roof guide sets out the difference. There are also unusual forms: the butterfly roof, with two slopes falling inward to a central gutter, and the curved or barrel roof, which is formed in metal or single-ply membranes.
How the timbers underneath are built
This is the part nobody sees, and it governs what you can do with a loft. UK pitched roofs are framed in one of two ways.
The older method is the cut roof, also called a traditional or cut-and-pitch roof. A carpenter cuts common rafters to length on site and fixes them to a ridge board at the top and a wall plate at the bottom. Heavier roofs add purlins, the horizontal timbers that run along the slope to support the rafters at mid-span, carried on struts down to internal walls. Collar ties or ceiling joists stop the walls from being pushed outward. Victorian terraces and pre-war semis in Basingstoke, Kingsclere and Overton generally have cut roofs, and the open loft space that results makes them popular for conversions.
The newer method is the trussed rafter roof, introduced widely from the 1960s. Factory-made triangular trusses, with their familiar W-shaped web of diagonal timbers joined by metal plates, are lifted on to the walls at close spacing. They are cheap, fast and strong, and they dominate the estates built around Basingstoke from the overspill era onwards. The web timbers are part of the structure, so they cannot simply be cut away for a staircase or a dormer. A loft conversion on a trussed roof normally means inserting steel beams and re-framing, designed by a structural engineer. The article on roof timbers explained names each member and what it does.
| Structure | Typical homes | What it means in practice |
|---|---|---|
| Cut roof with purlins | Victorian and Edwardian terraces, 1930s semis | Open loft, easier to convert, timbers can be old and need checking |
| Trussed rafters | 1960s onwards, estates and extensions | Webbed timbers must stay in place, conversions need steelwork |
| Hipped frame | Detached houses, bungalows | Extra hip rafters and more capping to maintain |
| Flat roof deck | Extensions, garages, porches | Joists and boards under a membrane, falls matter |
| Mansard frame | Town houses, some conversions | Steep lower slope, flat upper surface, many corners |
What the structure means for repairs and re-roofing
The covering you see is only the top of the system, and what is underneath sets the limits. The pitch decides which coverings are suitable, since tiles need a minimum slope to shed water, as our guide to the minimum roof pitch for tiles explains. The weight of the covering matters too. Moving from a lighter concrete tile to heavy natural slate or clay can put extra load on a frame that was designed for something lighter, and a big jump in covering weight is something building control looks at before the work starts.
The timbers decide how much work a repair can be. On a sound cut roof a damaged rafter foot can be sistered, that is, bolted alongside a new length. A trussed rafter, by contrast, should never be altered without engineering advice, because a cut web can weaken the whole truss. If we see a sagging ridge, cracked purlin or bowed rafters from the loft, we say so in the survey with photographs.
Pitch, wind and exposure
The angle of a roof is more than a style choice. A steep slope sheds rain and snow quickly and lets a small tile lap do its job, but it presents a larger face to the wind and costs more to scaffold. A shallow slope is cheaper to build and keeps the house lower, but water moves slowly across it, and tiles or slates need a deeper lap and good underlay to stop wind-blown rain being pushed upward under them. Some 1960s and 1970s houses on estate roads have a low pitch of this kind, which is why a tired felt underlay under a concrete tile roof can leak in a gale even when every tile looks in place.
Exposure changes which shapes cope best. Hipped roofs have no flat gable face for the wind to push against, so they suit open, high sites. Gable ends need a well-fixed verge, because wind catches the exposed edge and can strip it. Where we find mortar-only verges on an older gable, we recommend mechanical fixing, because BS 5534:2014, the British Standard for tile and slate fixing, no longer treats mortar as enough to hold the ridge, the hips or the verge.
Choosing a shape for a new build or extension
If you are planning an extension, the form of the roof is a design decision with a long tail. A pitched roof usually lasts longer between repairs and gives usable space in the roof void, but it needs height and works best when it matches the main house. A flat roof is cheaper to form, keeps the profile low and suits a modern look, but it needs better detailing and more attention over the years. Planning rules on height and appearance apply, which the council's planning officers can confirm for your plot, and building control will want the structure designed to carry the loads.
Whatever the shape, ask for the build-up in writing: the rafters or joists, the insulation, the underlay and the covering. A well-built roof of any form will outlast a poorly built one of any other.
Getting your own roof identified
If you are not sure what you have, a survey will tell you. We look at the outside and from the loft, name the structure and the covering, and explain what that means for repair, re-roofing or conversion. You receive photographs of your own roof and a written quote that is fixed. The work carries a 10-year workmanship guarantee, written down. For a view of how these roofs sit within the Basingstoke area, see our page on the town's housing stock and its roofs, or go back to the main page. To arrange a visit, ring 01256 213956 or use the WhatsApp line.
