Torch-on felt roofing across Hertfordshire

Price per m²

£63–£110

Typical life

15–25 years

Manufacturer guarantees

10–20 year material guarantees on specified systems

Typical garage roof

£1,600–£2,750

How much does a torch-on felt roof cost in Hertfordshire?

Guide prices including VAT at East of England rates. The fixed price comes after a free survey for new and replacement roofs.

Which flat roofs are common in Hertfordshire?

Flat roofs in Hertfordshire sit on lock-up garage blocks on estates, terraced streets with flat-roofed rear kitchens and bathrooms and 1930s semis with flat-roofed garages and kitchen extensions. The East of England is the driest part of Britain, with parts of the Anglian region around 630 mm a year, so summer heat and UV, not rainfall, do most of the ageing on a felt roof. 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 Hertfordshire the application goes to Watford Borough Council, Dacorum Borough Council, Stevenage Borough Council and 7 other councils. More on the rules.

Does replacing a felt roof mean upgrading the insulation?

Usually, yes, when the roof is over a heated space and more than half of it is being re-covered. In England, Wales and Northern Ireland that is renovation of a thermal element, which should be brought towards the renovation U-value where feasible; a Scottish project goes through the council's building standards service, which confirms whether a warrant applies.

A felt replacement is a good point to switch to a warm roof, with insulation laid above the deck under the new membranes. On larger roofs, tapered insulation can also correct poor falls that have caused ponding, which a patch repair cannot fix. Raising the roof level affects upstands and door thresholds, so we check heights at survey. Any approval is arranged by us as part of the job, and the building regulations page sets out the rules by nation.

Is torch-on roofing safe, and what is the difference between two- and three-layer systems?

Yes, torch-on is safe when hot works are properly controlled, because most roof fires linked to torching start at hidden timber or debris near edges and upstands, not on the open roof. Our teams follow a hot-works routine on every job:

• check eaves, fascias, soffits and wall cavities for timber, nests and debris before lighting a torch;
• use a cold-applied or self-adhesive membrane, rather than a flame, at edges, against combustible materials and in tight details;
• keep fire extinguishers on the roof and the gas bottles secured and away from the work;
• stop torching well before the team leaves, then carry out a fire watch so smouldering is spotted while people are still on site.

As for layers, a two-layer system (underlay plus cap sheet) is common on domestic roofs such as garages and extensions. A three-layer system adds an intermediate sheet, giving more thickness and redundancy, and is often specified on larger, commercial and multi-occupied roofs. The right choice depends on the size and use of the roof and the system's requirements, so we set it out in the quote.

Near a boundary, the external fire performance of the tested build-up, such as a BROOF(t4) classification, can also matter, and we check it where it applies.

Which towns in Hertfordshire do we cover?

• Watford
• Hemel Hempstead
• Stevenage
• St Albans
• Welwyn Garden City
• Cheshunt
• Hatfield
• Bishop's Stortford
• Borehamwood
• Hitchin
• Hoddesdon
• Letchworth Garden City
• Harpenden
• Bushey
• Hertford
• Rickmansworth
• Potters Bar
• Berkhamsted
• Ware
• Royston

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