Failed felt
Old felt patched over and over on both sides of a ridge, stripped back and done again.
Flat roofing
Three-layer torch-on felt with a mineral cap sheet, lead flashings and coping.
Find us and review us on
What people ask for
Before and after
Old felt peeling across the whole roof, stripped and finished in a new mineral cap sheet.
A 30m2 flat roof the team lifted and relaid with a 3 layer torch felt systemPro Build, job notes, 22 September 2026
Materials and options
Kane replied to my enquiry, came round to quote and completed the work - repairing and re-felting our flat roof in less than 2 weeks. And now I have peace of mind for the winter.
What moves the price
Square metres, then the deck under the felt: sound boards take the new layers straight away, soft ones are cut out first. Upstands and rooflights add detail.
How we price a job, in full
Square metres set the base of a flat roof price, and one roof in our job notes was 30 m². What changes it from there is the deck under the felt. If the boards are sound, the old felt comes off and the new layers go straight on; if water has been getting in for a while, the boards can be soft or rotten and have to be cut out and replaced before anything else, and that is only known once the old covering is up. The number of layers matters, because a three-layer torch-on system costs more than a single sheet and lasts much longer. Every upstand, every wall the roof meets, every rooflight and every outlet needs its own detailing, with lead flashing where the roof meets brick and coping where there is a parapet. Gutters and fascias are often worth doing at the same time, as on the September job. Access is the last part: a ground-floor extension can be reached from a ladder or a tower, while a roof between two pitched roofs may need scaffold. Replacing a flat roof can also bring building regulations into it, because the insulation may need upgrading.
Questions
Do I need building regulations to replace a flat roof?
Some flat roof repairs do not need building regulations approval. If a flat roof with built-in insulation is being replaced, you may have to upgrade the insulation to cut the heat lost through it.
Source: Roof: Building regulations: Re-roofing, Planning Portal (PortalPlanQuest Ltd, joint venture of TerraQuest and MHCLG)
Does a roof repair need building regulations approval?
Repairing or re-covering a pitched or flat roof does not normally need a building control application if less than 50 per cent of the roof, and less than 25 per cent of the whole building envelope, is affected. You will need approval if you go over those limits, make structural alterations, use a covering that behaves very differently in a fire, or use a covering that adds 15 per cent or more to the weight.
Source: Roof: Building Regulations: Work to an existing roof, Planning Portal (PortalPlanQuest Ltd, joint venture of TerraQuest and MHCLG)
More about flat roofing
Our team strips and relays flat roofs on extensions, garages and the flat sections between pitched roofs: a three-layer torch-on felt system with a mineral cap sheet, lead flashing where the roof meets a wall, and concrete coping on any parapet.
