Most homeowners haven’t heard of Dryseal before they start getting quotes for a flat roof. They’ve often heard of “fibreglass roofing” or “GRP roofing” as a general term, but Dryseal specifically is a name that tends to come up when they’re speaking to a contractor who actually uses it. This article explains exactly what the Dryseal system is, how it differs from other GRP approaches, and why the manufacturer warranty matters more than many homeowners realise.
What is GRP?
GRP stands for Glass Reinforced Plastic — it’s fibreglass. It’s the same fundamental material used to make boat hulls, car body panels, industrial tanks, wind turbine blades and a wide range of engineering components where you need something that is simultaneously lightweight, rigid and completely waterproof. When manufactured correctly, GRP is extremely durable: it does not rust, it does not rot and it does not absorb water.
In roofing, GRP is used to create a seamless, rigid waterproof shell over a flat or low-pitched roof deck. Unlike felt, which is a layered flexible membrane, or EPDM rubber, which is a stretched sheet, GRP forms a hard, monolithic surface once cured. This is one of the key reasons it outlasts other flat roofing materials by a considerable margin — there are no seams or joins to fail, and no flexibility to be lost over time.
Traditional GRP (wet lay-up) vs Dryseal
Not all GRP roofing is the same. The traditional approach — still used by many contractors — is called wet lay-up. In this method, fibreglass matting is cut to size on site and a liquid resin (usually polyester-based) is mixed and applied by hand on the roof deck. The resin cures in place, bonding the matting to the deck and creating the waterproof layer.
Wet lay-up can produce an excellent result, but it has significant variables: the resin mix must be correct, the temperature and humidity must be within the right range for the resin to cure properly, and the quality of the finished roof is heavily dependent on the individual skill of the person applying it. On a cold or damp day — which in Birmingham and the Midlands covers a large portion of the working year — wet lay-up can produce a roof that never cures to its full strength, resulting in a system that underperforms its theoretical lifespan.
Dryseal takes a fundamentally different approach. Rather than mixing resin and laying matting on site, the Dryseal system uses factory-manufactured, pre-cured GRP panels. The panels arrive on site already formed and quality-assured. A cold-applied resin is used at the joints and edges to bond the system together — no heat, no naked flames, no torching. The result is a roof whose core material quality is controlled in a factory environment rather than depending on site conditions.
What is Hambleside Danelaw?
Hambleside Danelaw is a UK building products manufacturer based in Daventry, Northamptonshire, who manufacture and supply the Dryseal system. They produce a range of roofing and building envelope products and have been active in the UK construction market for decades.
The Approved Installer designation matters here. To install Dryseal and offer the manufacturer warranty, a contractor must be trained and assessed by Hambleside Danelaw and registered on their Approved Installer programme. SB Margan Roofing is an Approved Installer — which means I’ve been through that training and assessment, and that the roofs I install can be registered for the 20-year warranty.
The warranty point is worth dwelling on. The 20-year Dryseal warranty is registered with Hambleside Danelaw, not with the roofing contractor. This is important for homeowners because it means that if I — or any other Approved Installer — were to go out of business, the warranty would remain valid and claimable directly through Hambleside Danelaw. You’re not relying on a contractor still being in business in fifteen years’ time. For more on what the flat roofing installation involves, see the service page.
Who is it suitable for?
Dryseal GRP is suitable for almost any flat or low-pitch roof section on a domestic property, including:
- Flat-roofed single-storey extensions
- Garage roofs
- Outbuildings and garden rooms
- Bay window roofs
- Dormer roofs and dormer cheeks
- Any flat section within a larger pitched roof
It works equally well on new builds — where a deck is being constructed from scratch — and as a replacement system over an existing felt or EPDM roof where the deck is in good condition. If the existing deck has deteriorated, it will need to be replaced as part of the job, which adds to the cost but ensures the system performs correctly over its full life.
What does installation involve?
A Dryseal installation follows a clear, repeatable process:
- Survey and measurement. The roof is measured, the deck assessed for soundness, and any necessary deck repairs or replacement identified. Outlet positions and falls are checked.
- Deck preparation. The deck surface is cleaned and any areas of damaged or soft boarding are replaced. The deck must be dry, sound and properly supported.
- Panel installation. The pre-cured GRP panels are cut to size and laid on the deck. The cold-applied resin is used to bond the joints between panels and to seal all upstands and edge details.
- Edge trims and outlets. GRP edge trims are fitted around the perimeter, and outlets are sealed into the membrane. These details are critical — most flat roof failures originate at edges, upstands and outlets rather than in the field of the roof.
- Final inspection and warranty registration. The completed roof is checked before leaving site, and the warranty is registered with Hambleside Danelaw.
No hot works permit is required, and the system can typically be installed in a single day on most domestic roof areas.
How much does a Dryseal flat roof cost?
This is always the question, and it’s one I can only answer accurately after seeing a specific roof. That said, for a typical single-storey extension or garage roof in Birmingham or the West Midlands, a complete Dryseal installation including deck preparation will usually fall in the range of £1,500–£3,500. Larger roofs, roofs with complex detailing, or roofs requiring significant deck replacement will sit towards the upper end or above that range.
The cost is higher than a felt re-cover, but felt and GRP are not equivalent products. A felt roof done cheaply will need attention in 10–12 years. A Dryseal GRP roof installed correctly should still be performing at 25 years with no maintenance beyond keeping outlets clear. Over a 25-year period, the GRP option is almost always the better value when you account for the labour and disruption of the interim felt replacement.
If you’d like an accurate quote for your property, I offer free surveys across Birmingham and Worcestershire. Get in touch to arrange a visit, or see the flat roofing service page for more information on the installation.