Flat roof repairs across London

Guide price

£180–£600

Repair price

Confirmed once the leak or damage is found

Condition survey report

£180–£360

Coverage

England, Wales, Scotland, NI

How much does a flat roof repair cost in London?

Guide prices including VAT at London rates. We confirm the price once we've traced the leak or seen the damage.

Which flat roofs are common in London?

Flat roofs in London sit on mansard and dormer loft conversions, kitchen extensions and roof terraces behind period houses and mansion blocks and purpose-built flats with large flat roofs. The Thames basin is one of the drier parts of Britain at roughly 730 mm of rain a year, but summer heat is the bigger test here: dark membranes on south-facing roofs swing a long way in temperature. Approximate 1991–2020 regional averages based on Met Office data.

Building regulations in England

Replacing more than half of a roof over a heated room usually counts as renovating a thermal element, so it is insulated to current standards and notified to building control. Renovated roofs over heated rooms are insulated to around 0.16 W/m²K where that's feasible, and new extension roofs are built to 0.15 W/m²K. In London the application goes to City of Westminster, London Borough of Camden, London Borough of Islington and 29 other councils. More on the rules.

Which repair materials work with my type of flat roof?

The repair has to use the same system as the roof, because many flat roof materials don't bond to each other and some damage each other.

• Torch-on felt: repaired with compatible bitumen membrane, cut back to sound felt and lapped well beyond the defect. Torching near timber, insulation or fascias needs care, and some details are better done with cold-applied methods.
• EPDM rubber: repaired with EPDM patches and the manufacturer's primer and seam tape. Bitumen products and many general-purpose sealants won't bond to EPDM and shouldn't be used on it.
• GRP fibreglass: the area is ground back, then new resin and glass matting are laid and finished with topcoat to match.
• Liquid-applied and single-ply: repaired with the same manufacturer's products wherever possible, as mixing systems can affect a material guarantee.
• Mastic asphalt: cracks and blisters are cut out and made good with new asphalt by an operative who works with it.

A tin of roof sealant or bitumen paint may stop a drip for a while, but on the wrong membrane it makes a proper repair harder later.

What do you check and do on a repair visit?

We inspect the whole roof, not only the spot that is leaking, and tell you what we have found before any work starts.

A typical visit covers the covering itself (splits, blisters, crazing, lost chippings and open laps), the upstands and flashings at walls, edge trims and drips, outlets and gutters, any rooflights, and how water sits on the roof after rain. Where it is safe to do so, we check the deck for soft spots. Every roof is treated as fragile until a competent person has confirmed otherwise, and edge protection goes in before anyone works near an open edge.

The repair itself means cutting back to sound material, drying the area and repairing with the same system. We clear the outlets while we are up there, because a blocked outlet is a common reason a repaired roof leaks again. What the repair covers, and what it doesn't, is set out in the written quote.

Which towns in London do we cover?

• Westminster
• Camden
• Islington
• Haringey
• Hounslow
• Barnet
• Bexley
• Lambeth
• Croydon
• Havering
• Lewisham
• Redbridge
• Southwark
• Bromley
• Ealing
• Hammersmith and Fulham
• Harrow
• Kensington and Chelsea
• Barking and Dagenham
• Brent
• Greenwich
• Hillingdon
• Kingston upon Thames
• Richmond upon Thames
• Sutton
• Waltham Forest
• Enfield
• Hackney
• Newham
• Tower Hamlets
• Merton
• Wandsworth

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