Flat roof replacement across Hertfordshire

Guide price

£2,950–£5,150

Survey

Free for new and replacement roofs

Quote

Fixed, in writing

Coverage

England, Wales, Scotland, NI

How much does a flat roof replacement 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 low-rise post-war blocks of flats, 1930s semis with flat-roofed garages and kitchen extensions and shops with flat-roofed rear stores below flats. 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.

Should I overlay my old flat roof or strip it fully?

Strip it fully if the deck is soft, the insulation is wet or the falls are wrong; an overlay only suits a dry, sound roof that already drains well. Covering a wet roof traps the moisture, and rot carries on out of sight.

An overlay also raises the roof level, eating into upstand height at walls and door thresholds, and every layer adds weight. In England, a covering that adds 15% or more to the roof's weight needs building control approval. Signs it is time to replace rather than repair:

• ponding that lingers long after rain
• blisters, cracking or crazing across wide areas
• bare bitumen where the mineral chippings have gone
• split laps and lifted upstands or flashings
• damp ceilings, or a deck that has gone soft
• leaks that return after each repair

A single defect on an otherwise dry roof can usually be put right with a repair. If you're unsure, a survey settles it, and our guides to overlay or strip and repair or replace go further.

Do I need building regulations approval to replace a flat roof?

Often, yes. Replacing the covering of a flat roof over a heated room is usually treated as renovating a thermal element, which brings insulation requirements and, in most cases, approval.

In England, if more than half of that roof is renovated, the whole roof should be upgraded towards a U-value of 0.16 W/m²K for homes (0.18 for non-domestic buildings) where that is technically, functionally and economically feasible, judged against a simple payback of 15 years. Approval comes from building control or self-certification through a registered competent person scheme. Structural changes, or a covering that adds 15% or more to the roof's weight, also need approval.

The other nations differ: most re-roofing in Wales needs approval, Scotland works through building standards and the building warrant, and in Northern Ireland you contact the district council's building control first. An unheated detached garage is not normally a thermal element. Planning permission is not usually needed if the roof looks much the same afterwards, though listed buildings and conservation areas are different. We handle approvals where needed; see building regulations.

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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