Flat roof insulation
Flat roofs on extensions, dormers and whole-house conversions are often the coldest part of a rented home. Insulating them, ideally when the roof covering is due for renewal, closes a gap the EPC assessor will otherwise assume is uninsulated.
What it is
Rigid insulation boards fitted to a flat roof, either above the roof deck under a new waterproof covering (a "warm roof") or between the joists from below with a ventilated void (a "cold roof"). We recommend the warm-roof build-up wherever the covering can be renewed at the same time, because it keeps the structure warm and dry and avoids the condensation risk that badly done cold roofs create. Typical thickness is 100 to 150mm of PIR board, taking the roof to current Building Regulations standards.
Why it matters for 2030
An EPC assessor who cannot see insulation in a flat roof records it as "as built", which for anything pre-2000 means little or none, and that drags the whole rating down. Kitchen and bathroom extensions with a flat roof are very common on Greater Manchester terraces and semis, so this is often the single measure that separates a stubborn D from a C. Fixing it also removes the damp patches and cold ceilings tenants complain about most.
Which homes suit it
Any rented property with a flat roof over habitable space — rear extensions, dormers, garage conversions, flat-roofed maisonettes and 1960s-70s houses with a full flat roof. If the felt or asphalt covering is more than 15 to 20 years old, combining the insulation with a new covering is the most economical route. Roofs over unheated garages or outbuildings do not count towards the EPC and we will tell you so rather than sell you the work.
Grants that apply
Flat roof insulation is an eligible measure under the Warm Homes: Local Grant for qualifying Greater Manchester tenants and under ECO4 while it runs (to 31 December 2026). The insulation element is zero-rated for VAT until 31 March 2027. Where a new covering is needed the roofing element is priced separately and is not usually grant-funded; we make that split clear in the quote. See the grants page for the eligibility rules.
How we do it
Surveyed and coordinated to PAS 2035, with a moisture and ventilation check before any design is signed off, then installed by our accredited partner LAMTANS Engineering to PAS 2030 standards and lodged with TrustMark. You receive a fixed price from our own price book, a Building Regulations completion certificate where the roof covering is renewed, and the evidence you need for the post-works EPC and your compliance file.
Common questions
Does the tenant need to move out?
No. A warm-roof upgrade is done entirely from outside; a cold-roof job from below usually takes one to two days per room and the tenant stays in place.
Can it be done without replacing the roof covering?
Yes, from below as a cold roof, but only where a 50mm ventilated gap can be kept above the insulation. If it cannot, we advise waiting to do a warm roof rather than creating a condensation problem.
Related: pitched roof insulation · loft insulation · room-in-roof insulation