Flat roofing in London: felt, EPDM and fibreglass with a 20 year guarantee

Flat roofing in London: where the capital leaks from the top

Most London houses carry a flat roof somewhere. The Victorian terrace has a kitchen extension at the back, the 1930s semi has a garage and a porch, and the loft conversion has a dormer with a flat top and flat cheeks. Each of those roofs is a few square metres of covering with a joint along every edge, and each edge is a way in for water.

A flat roof does not fail all at once. It ponds at the low point, the felt blisters, the upstand pulls away from the wall and the outlet blocks with leaves. By the time the ceiling stains, the deck underneath has been wet for months. That is why flat roofing in London is better repaired on the first sign than replaced after the second winter.

Felt, EPDM or fibreglass: choosing the right system

We lay all three, and the right one depends on the shape of your roof, not on what is cheapest to stock. This table sets out where each one suits.

Whichever system you choose, the work carries the same 20 year written guarantee and the same itemised written quote.

• Felt roofing: proven, repairable and good value on larger areas
• EPDM rubber roofing: one sheet, long lengths, fewer places to leak
• GRP fibreglass roofing: moulded to the roof, ideal where details are tight

Flat roof repair in London: when a patch works

A patch works when the covering has split in one place and the deck underneath is dry and firm. We cut out the failed section, dry the deck, lay the new piece and dress it into the old with the correct overlaps. It is quick, it is guaranteed and it costs a fraction of a new roof.

A patch does not work when the felt has blistered across the roof, the roof ponds all over or the boards have gone soft. Then every repair is a short extension of the leak. We probe the deck, show you the photographs and give you two written prices: the repair and the replacement. Flat roof repair in London is honest work when the choice is yours.

Signs your flat roof is failing

Any one of these is a reason to book a survey. A free inspection costs nothing, and it tells you whether you need a repair this month or a new roof next year.

• Water standing on the roof 48 hours after rain
• Blisters, ridges or cracks in the felt, especially along the edges
• A soft or springy feel underfoot where the deck has absorbed water
• A damp patch on the ceiling below that grows after heavy rain
• Moss, weeds or seedlings at the outlet or along the gutter edge
• Felt lifting where the roof meets the wall

Warm roofs, cold roofs and the Building Regulations

Replacing most of a flat roof brings the insulation standard of the Building Regulations into play, so insulation belongs in the quote, not in a later conversation. A warm roof puts the insulation above the deck, keeps the structure warm and avoids the condensation that rots a cold roof. A cold roof insulates between the joists and needs a ventilated void.

We tell you which build-up your roof can take, price the insulation and the deck together and fit a new OSB deck with the covering on top. The aim is a roof that does not come back in five years. A new deck also lets us correct the falls, so water runs to the outlet instead of sitting on the roof.

Dormers, rooflights and roof lanterns

Loft conversions put flat roofs in awkward places: the top of a dormer, the cheeks either side, the kerb round a rooflight. Each one needs lead or a matching upstand dressed into the tiles or the wall. Fibreglass handles these shapes well because it is laid in one piece.

Kitchen extensions can carry a glazed roof lantern in the middle of the flat roof. We build the kerb, lay the covering up to it and seal the junction. See our flat roof with roof lantern project for how the finished roof looks.

How a flat roof replacement runs

A full replacement follows the same order on every job, so you know what happens each day.

• Edge protection or scaffold goes up and the area is made safe
• The old covering is stripped and taken away
• The deck is checked, and any soft boards are replaced with new OSB
• Insulation is fitted to the build-up we agreed in the quote
• The new covering is laid, with upstands, flashings and drip edges
• Outlets and gutters are connected and tested
• The site is cleared and the 20 year written guarantee is handed over

Where flat roofing in London goes wrong on terraces

On a Victorian or Edwardian terrace the flat roof sits at the back, against the main wall and against the neighbour's wall as well. The weak points are the flashing where the new roof meets the old brickwork, the outlet that takes the water to the downpipe and the parapet gutter at the party wall.

We repoint the chase, fit a proper lead or EPDM upstand and set the falls so water leaves the roof. If you share the wall, we tell the neighbour when we are on site.

The joists under a rear addition on an older terrace were never designed for insulation. If they are sound we build on them, and if they have rotted we replace them before the deck goes down. You see the timber before it is covered.

Garage and porch roofs

Garage roofs and porch roofs are the smallest flat roofs on the street and the ones left until they leak. A garage roof is mostly a simple rectangle, so felt or EPDM works well and the job is quick. A porch roof is smaller still, with a bay or canopy shape that suits fibreglass. We treat both as seriously as a full extension, with a proper deck, upstands and a written guarantee.

Scaffold, hot works and parking for flat roofing in London

Many flat roofs are low enough to work from a tower or a short scaffold, but edges still need protection and materials still need to arrive. On a terrace that means a pavement scaffold and a highway licence from the borough, a skip permit and a parking permit for the van. Any third party charges are listed in your written quote.

Torch-on felt needs fire precautions, so the risk assessment before every job sets out the hot-works controls. Our garage roofs page covers outbuildings, and the flat roof cost guide explains what drives the price.

Where we do flat roofing across London

We work from Dunstable, about 22 to 31 miles from the North London areas below. For housing and the rules in your street, see Harrow, Barnet, Enfield, Edgware, Wembley and Pinner, or return to the North London hub. For leaks, start with our London roof repairs page.

Written price, written guarantee

Every flat roof quote is free, with no obligation, in writing and itemised between materials and labour. We promise to beat any written quote. All work is backed with a 20 year written guarantee, and we are fully insured and a family business with over 25 years' experience. Get your free quote.