Find a local flat roof specialist

Flat roof- installation / repair specialists - what you need to know

There are many reasons you might be looking at a flat roof – from planning restrictions through to budget, architecture and even thermal efficiency. Whatever your motive, modern flat roofs are neat and can be an elegant, cost-effective solution for a single-storey extension or garage.

The name “flat roof” is actually slightly misleading – all so-called flat roofs need a slight angle or “pitch” to allow rain water to drain. Puddles are the enemy of any flat roof, as standing water can cause leaks or damp.

Flat roofing systems require a level base, or roof deck, to apply a waterproof membrane to. The deck layer is usually created using timber or plywood for domestic roofing, but might also be made from metal, concrete, or a composite.

If your tradesperson uses plywood, it should be at least 18 mm thick, with sheets fixed to joists along their longer edges and staggered for greater stability. A membrane will then sit on the plywood deck, allowing for an expansion gap (if necessary). Typically, membranes consist of asphalt, EPDM, or bitumen on older roofs

Cost of flat roofing

• Budget (felt roofs): £40 average price per sqm
• Medium (rubber or fibre glass roofs): £80-£90 average price per sqm
• Expensive (lead bay roofs): £300+ average price per sqm

What materials are flat roofs made from?

Flat roofs consist of a few layers, each using a specific material for a specific purpose. As we’ve mentioned above, the deck layer will be constructed using plywood, sheet timber, metal, concrete, or a composite.

Vapour control and thermal layers may also be required, sitting between the deck and the waterproofing membrane. Vapour control is provided by sheets made from polymeric foil, bitumen sheet, or polyethylene membrane, while the thermal layer is typically standard insulation – fibreglass or mineral wool.

There are a number of options for the top waterproof layer, such as bitumen-based felt or asphalt, EPDM rubber and PVC systems. Stone chippings or a mineral finish are usually added to protect the waterproof layer.

Can flat roofs be repaired?

Most flat roofs can be fixed by a professional with the right expertise. It’s worth noting that running repairs may be an ongoing cost consideration if you own a property with a flat roof. The most common issue you’ll face is the build-up of dirt which prevents rain from draining – causing standing water and leaks. Cleaning away dirt is an easy issue to solve.

Provided there isn’t extensive damage to the roof, typically repairing blistered felt, splits or cracks, and replacement flashings can solve the problem. A roofing expert will be able to find the issue and advise you regarding whether a repair is cost-efficient (and likely to last). 

Don’t be tempted to try to repair a flat roof by yourself though. Even roofs that aren’t too old may not be as stable as you think, and it can be dangerous to clamber around with rotten areas or weak points.

The qualifications your tradesperson needs

There’s no legal requirement for a flat roofing tradesperson to hold a specific qualification or accreditation. It’s advisable to opt for a roofing specialist, rather than a general builder, and specifically one with generous flat roofing expertise.

A number of City & Guilds and NVQ qualifications are available, specific to flat roofing. While these are an advantage, they’re not compulsory. Similarly, the National Federation of Roofing Contractors (NFRC) is a trade body that some roofers will have a membership to, but it’s not crucial.

Planning permission for flat roofing

Flat roofing is often a solution to planning concerns, but you should always check with a planning officer rather than assuming your project won’t need additional permission. The main concern with a flat roof is the structure it sits on top of – an extension or a new garage may require planning permission, even if they are only single storey.

If your property is in an area that features older buildings, or a neighbourhood that has homes with a specific architecture, visual amenity (in other words the “style” of your project) may come into consideration too. While modern flat roofs are unobjectionable, the quirks of local government can always spring a surprise.

Read the full list of planning permission considerations on the planning portal website, and if in doubt speak to your local council.

Insurance for flat roofing work

Alongside public liability insurance – crucial to protect you and your property against any damage a tradesperson causes – ask for a warranty on the roof. The last thing you’ll want is a leak which leads to a downpour inside your home, and an outpour from your wallet.

Questions you should ask your flat roofing specialist

• What materials would they use for your flat roof, and why?
• Can they provide a warranty for their work?
• Can they show you their public liability insurance?