Prefix WARMroof review

WARMroof is an insulated tiled roof that replaces the glass or polycarbonate roof on an existing conservatory. It comes from Prefix Systems, a Lancashire roof maker that was one of the early names in solid conservatory roofs. Since January 2025, when the original Prefix companies went into administration, the brand has traded as a division of Ultraframe (UK) Ltd.

If you are comparing quotes, WARMroof is a trade product you will meet through an installer rather than a brand you buy direct. If you already own a Prefix roof, the change of ownership affects who stands behind the original product guarantee.

Who makes the Prefix WARMroof?

According to a Glass Times profile we could not re-check, Chris Cooke founded Prefix in 1996 in a small unit in Bacup, later moving to Accrington and, in 2015, to a 60,000 sq ft site in Blackburn, with further plants in Northampton (2006) and Swansea (2010).

Companies House shows what happened next. Prefix Systems (UK) Ltd (03995507, incorporated 17 May 2000) entered administration on 8 January 2025, with administrators from Leonard Curtis in Manchester, and was renamed PS2 Realisations 2025 Ltd in February 2025. Prefix Systems Holdings Ltd entered administration the same day, and the Prefix Systems (South) and (SW) companies are also in administration.

Prefix now calls itself “a trading division of Ultraframe (UK) Ltd” and gives Ultraframe’s company number, 01765701. Ultraframe has traded since 1983 and has no insolvency record. The date and terms of the move are not confirmed. Prefix also sells glass roofs, Stratus lanterns, orangeries, verandas and Ultraframe’s LivinRoof.

How the WARMroof is built

Prefix describes WARMroof as a ridge-free A-frame design:

1. A 15mm plywood base panel with 100mm of base insulation.
2. An extra 70mm phenolic insulation top panel laid over the bars, which Prefix says avoids thermal bridging.
3. A breathable waterproof membrane.
4. Lightweight tiles or slates.
5. Fully insulated eaves.

The roof is delivered on pallets, with Velux roof windows fitted in the factory if you choose them. The WARMroof Hybrid version adds glazed panels in variable positions, with 28mm double glazing as standard or optional 44mm triple glazing. If you are weighing up glazed panels, see our comparison of tiled and hybrid roofs.

Prefix WARMroof specifications

Specification	Prefix WARMroof
U-value (maker’s figure)	0.18 W/m²K standard UK, 0.15 Scotland. ExpertSure quotes 0.15
Weight	Not published
Design	Ridge-free A-frame; 100mm base insulation plus 70mm phenolic over the bars
Tile finishes	Modern Tile (square nose), Envirotile, Britmet LiteSlate, Tapco Slate
Colours	Envirotile: Anthracite Black, Slate Grey, Dark Brown and one other. LiteSlate: Charcoal, Ash, Slate, Oak, Amethyst, Sunshine, Sunset. Tapco: Stone Black, Pewter Grey, Plum, Brick Red, Chestnut Brown, Red Rock
Glazed options	Factory-fitted Velux roof windows; WARMroof Hybrid with 28mm double or 44mm triple glazed panels
Certification	Stroma approved (thermal performance); fire tested and rated (Prefix). LABC Registered Detail EWS481 appears in LABC search results (not re-checked)
Guarantee	Not stated on the WARMroof page; ExpertSure lists Prefix with a 10-year warranty

Why the U-value matters

Prefix’s standard figure of 0.18 W/m²K is higher than the 0.15 most rivals quote, with 0.15 offered only for Scotland. Approved Document L sets 0.15 as the limiting U-value for a new roof element in an existing home in England, and LABC treats a solid replacement roof as a new thermal element. Ask your installer what U-value your roof will actually be built to, and how building control will approve it. Our guide to what a warm roof is explains how the insulation layers work.

Prefix WARMroof cost in 2026

We found no WARMroof-specific price, and ExpertSure lists Prefix as quote-only. The nearest benchmarks are ExpertSure’s £8,000 to £12,000 for a tiled roof on a standard 4m x 4m Victorian (July 2026), and our researched range of £7,400 to £12,100 fitted for tiled roofs on a medium conservatory, typically about £9,600. See our tiled roof cost guide.

Who sells and fits WARMroof?

Prefix is a trade-only supplier. Its website points homeowners to approved installers through a “Connect With Installer” option. We found no published count of WARMroof installers.

Reported problems and reviews

We found no Trustpilot profile for Prefix Systems and no pattern of owner complaints in our research. The issues we can document are:

• The administration. Anyone with a Prefix roof supplied before January 2025 should know the original product guarantee was issued by companies now in administration, and we found no public statement on who honours those guarantees. Citizens Advice says that if a company goes bust you can register as a creditor but might not get any money back. Your installer’s workmanship guarantee, and any insurance-backed guarantee, is separate. Our guide to roof guarantees explains the difference.
• The standard U-value of 0.18, covered above.
• Name confusion. “Warm roof” is a general term and several brands use it. ExpertSure’s “WARMroof” listing (timber frame, 25-year guarantee) appears to describe a different product, so check that any review you read is about Prefix.

WARMroof vs UltraRoof, Guardian and Equinox

	Prefix WARMroof	UltraRoof 380	Guardian	Equinox
U-value (maker)	0.18 (0.15 Scotland)	0.15	0.15 (England)	As low as 0.15
Weight	Not published	38 kg/m²	About 55 kg/m² (third party)	67 kg/m² (third party)
Glass	Velux or hybrid panels	Glass panels or roof windows	Solstice panel or VELUX	Roof windows or Vega panel
Guarantee	Not stated by Prefix	10-year parts	10 + 10 years, insurance-backed	10 years

Ultraframe now owns both WARMroof and UltraRoof 380, and UltraRoof quotes the lower standard U-value. See our UltraRoof 380 review.

Verdict: who WARMroof suits

WARMroof suits you if an installer you trust fits it, you like the ridge-free design and factory-fitted Velux windows, and your specification meets the U-value building control needs. It suits you less if you want a published price, a stated manufacturer guarantee or a 0.15 U-value as standard in England.

When you get quotes, ask the installer for the U-value of your roof in writing, the length and backing of the guarantee now that Prefix sits within Ultraframe, and who submits the building control application.