Gelligaer at a glance
- Postcode districts
- CF82
- Population
- about 17,376 (GeoNames)
- Council area
- Caerphilly County Borough Council
- Building approval
- Caerphilly County Borough Council building control, or a registered building control approver
- Nearest main town
- Caerphilly, about 6 miles
- Guide price region
- Wales (−8% on West Midlands rates)
Why upgrade to a warm roof in Gelligaer?
Many flat-roofed extensions and dormers in Gelligaer were built with little or no insulation, or with a cold roof that was never properly ventilated. Those rooms are often hard to heat in winter and can suffer condensation, mould and, in time, a rotten deck.
Gelligaer's flat roofs are mostly on 1930s semis with flat-roofed garages and kitchen extensions, with plenty on bungalows with flat-roofed side extensions and dormers too. Wales averages roughly 1,460 mm of rain a year, among the wettest in Britain, so we design for steady run-off: proper falls, clear outlets and upstands well above the finished roof.
How much does a warm roof upgrade cost in Gelligaer?
Guide price in Gelligaer: £2,600–£4,500 for a 20 m² extension roof in EPDM with a new deck and insulation, including VAT at Wales rates. The fixed price comes after a free survey for new and replacement roofs.
| Job | Guide price inc VAT |
|---|---|
| Extension (20 m²), EPDM, new deck + insulation | £2,600–£4,500 |
| Extension (20 m²), EPDM with sedum green roof | £4,050–£7,450 |
Will insulating the roof raise its height, and what about doors and upstands?
Yes. A warm roof makes the roof thicker, often by more than 100 mm depending on the insulation and the U-value target. That extra height is the main thing we plan around.
Waterproofing at a wall usually needs to rise about 150 mm above the finished roof surface, so if the roof gets higher, the upstand has to go higher too. That can be a problem where the roof meets a door threshold, a low window sill, a cavity tray or a rooflight kerb. At the edges, trims and fascias are reset to the new level, and gutters may need to move.
Where there isn't enough height, the options include using thinner, higher-performance insulation, lowering the deck where the structure allows, raising the sill or threshold, or, where it is genuinely not feasible to reach the full target, insulating as far as is reasonable and recording why with building control. We work this out at the survey so there are no surprises on the day.
What's included?
- Vapour control layer on the warm side of the insulation
- New waterproofing, with a written workmanship guarantee
- Building control or building standards handled where needed
- Upstands, trims and kerbs reset to the new roof level
Building regulations in Wales
The Welsh Approved Document L applies. Renovating more than half of a roof over a heated room means upgrading it to around 0.16 W/m²K where feasible, and new extension roofs are built to 0.13 W/m²K. Welsh Government guidance is that most re-roofing needs building control approval, so check whenever more than a quarter of a roof is replaced or repaired. We deal with the application as part of the job. More on the rules.
Which nearby areas do we also cover?
Warm roof insulation upgrades in Gelligaer: questions
Do you cover Gelligaer?
Yes. Gelligaer is part of our Caerphilly coverage, including postcode districts CF82. Surveys and roofs are carried out by vetted roofing teams working under S&K Property Investments and Improvement Ltd.
Who checks building regulations for a flat roof in Gelligaer?
Where the work needs approval it goes to Caerphilly County Borough Council building control, or a registered building control approver. We tell you at the survey whether your job needs it and deal with the paperwork as part of the quote.
How much does a warm roof upgrade cost in Gelligaer?
£2,600–£4,500 for a 20 m² extension roof in EPDM with a new deck and insulation, at Wales guide rates including VAT. The fixed price comes after a free survey for new and replacement roofs.
How thick does flat roof insulation need to be?
It depends on the insulation product and the U-value target. With common PIR boards, meeting a renovation target usually means well over 100 mm. Thinner, higher-performance boards are available where height is tight.
Can you insulate a flat roof from inside instead?
It is possible, but insulating between or under the joists creates a cold roof, which needs ventilation and carries a higher condensation risk. When the roof is being re-covered anyway, a warm roof from above is usually the better option.