Ap-ply-ing a different pitch to roofing

By Martin Shave, business development manager for domestic roofing at Protan.

Why do we build dwellings with pitched, tiled roofs? There is no law saying we have to; it is tradition, and a bad reputation for flat roofs. Yet a move away from the traditional would create a more interesting vista, give housebuilders greater profit potential, and go a long way to major reductions in the £2.5 billion we spend repairing roofs damaged by weather.

Twenty-three per cent of Britain’s existing dwellings already have at least some part of the roof that is flat/low pitched. Current consumer demand is for maximum natural light and open plan living. As a result, housebuilders are responding to the consumer demand by incorporating bifold doors into properties, often under a low pitched roof. These low-pitched structures, in effect, give consumers the ready-made extension they would probably add anyway (instead of a conservatory). It meets the demand for more light within, and has an ‘added value’ benefit in that should they want to add more upstairs space, the base is already there.

People also want something different: choosing an alternative to a conventional pitched, tiled roof gives architects massive scope to let their imagination flow.

We are experiencing a spate of windier, colder winters. Research shows that when we suffer high winds, domestic roof damage exceeds £2.5 billion, as tiles lift under wind loading; in winter weather, roof damage is the most common insurance claim as tiles crack from the cold or give way under snow loading.

If we constructed roofs with ‘softer’ lines, and used different roofing materials, such as single ply membranes, much of that weather damage could be eliminated.

Historically, flat roofs in the domestic sector have been avoided, based on their reputation for problems and failures. Admittedly, too often they have failed largely because of a tendency to go for as low a cost as possible – meaning inferior materials, often poorly installed.

The reality is that if properly designed to modern standards, using decent materials, flat roofs covered with a membrane will perform as well as – if not better than – pitched, tiled roofs. They will also compare favourably in terms of material costs and significantly reduce labour costs.

The minimum quality of roofing for built-up roofs on habitable buildings is Bs747 Type 5. Today’s single ply membranes are a world apart from traditional rag, wood-fibre or asbestos based felts. PVC membranes, for example, have overcome their main problem from the 1950s of becoming brittle, helping ensure their longevity in practice. Today, there are PVC roofs that have been in place, without detriment for 35+ years.

To go beyond flat roofing, single ply membranes help deliver the energy efficiency requirements laid down in Approved Document L, and, under the Green Guide, achieve a A+ rating. Properly installed there will also be fewer potential site remedials/snagging than with a tiled roof with mortar-bedded ridge and eaves.

The National Federation of Roofing Contractors (NFRC) and Single Ply Roofing Asssociation (SPRA) have both published guides on designing a built-up roof, both of which reiterate that message: good quality installation by reputable contractors will give a dependable, long-lasting roof.

A single ply roof can be warm or cold in its construction. It does not have to be flat. The roof is the fifth elevation of a building, and should give as much architectural and aesthetic interest as the supporting walls. The nature of the beast with single ply membrane is that it is a flexible material. As a result, it is ideally suited to almost every roof. It can be more easily fitted into valleys and gutters. It can be manipulated through all dimensions, enabling curves, barrels and angles to be formed almost seamlessly. It can be manufactured in almost any colour. It forms the basis of a green roof.

So I go back to my original question. Why do we build pitched, tiled roofs? Follow the lead of Avant Group, Wandle Housing Association, Selco Eco Village and a myriad others: go the single ply route.