Back to Basics: How is GRP used in roofing?

Glass fibres were used in the days of the Ancient Egyptians to strengthen clay jars and pots, and for decoration.  However, the possibilities of GRP were not fully realised until the British military experimented with the material during WW2, it was then used for boat building, radar equipment and aviation components.

Today, the uses of GRP are extensive, with the material being used in everything from aerospace engineering to building materials.  Hambleside Danelaw have long understood the benefits of GRP and have developed a wide array of products that use the versatile substance, from flat roofing to rooflights.  Glass Reinforced Plastic provides a host of solutions for various roofing requirements.  Our range of GRP profiles for pitched roofing are generically classed as ‘flashings’, but how can GRP be used in roofing, and how can this benefit and enhance developments?

Danelaw Dry Fix Valley Trough HDL DVS

Valley Troughs

Hambleside Danelaw originated the use of valley troughs manufactured from GRP as an alternative to using lead sheet and are used in inclined roof valley details.  GRP holds less scrap value than lead, deterring thieves and thereby preventing unnecessary damage to the building.  GRP Valley Troughs do not streak or stain and can be used to collect rainwater run-off from the roof without harmful run-off into watercourses and water reclamation systems.

We produce Valley Troughs for all types of slate and tile roofs, for use with mortar and dry fixed, with different options depending upon the roof requirements.

Bonding Gutters®

Bonding Gutters® are used to protect an area where two different types of tiles or slates join on a roof slope.  For example, where double lapped tiles are next to single lapped tiles.  In these instances, the two types do not interlock, creating a weak point where moisture could penetrate the roofing structure.  Traditionally formed from polymer-based materials or lead, Bonding Gutters are used to weatherproof that point of weakness.

GRP is durable, waterproof, and can cost much less than lead.  We manufacture both Low Profile and High Profile Bonding Gutters® for dry fix applications, as well as a traditional design for mortar-based applications.


In houses where there is a vertical abutment protrusion through the roof, such as a chimney, it becomes necessary to waterproof the junction with the tiles.  Soakers are installed at this point, below the slates or tiles to form a weatherproof detail.

Hambleside Danelaw produce continuous soakers (Contisoakers® or secret gutters) from GRP with an option for use in conjunction with a cover flashing (also available in GRP), or lipped for securing into a chase in the wall, depending on your project needs.

Danelaw Continuous Verge HDL DV9

Continuous Verges

When fitting or refurbishing a slate roof it is important to ensure that the roof is weatherproof from all angles.  The continuous verges for slate roofs made by Hambleside Danelaw prevent water ingress and offer a neat and lightweight solution to weatherproofing. To meet the needs of a variety of projects  Danelaw produce continuous verges that incorporate a fixing flange that is concealed when used in new build or re-roofing, or to be faced fixed to the barge board or gable of the building.

The range includes GRP continuous verges for slate roofing practice as used in Scotland.


A world of possibilities

There are a wide variety of GRP solutions for slate and tile roofs, some not mentioned here, that can be used to weatherproof and secure a building’s roof.  With dry fix now a standard method of installation for roofing, GRP products should be the first port of call for security and durability.

All of Hambleside Danelaw’s flashing products come with a 30-year service life guarantee, meaning developments utilising them can remain leak-free for years.

Hambleside Danelaw offer the widest range of ancillary products for pitched roofing, want to learn more about our GRP roofing products?  Browse our range or get in touch with one of our online stockists.

The benefits of GRP as a construction product material  are also used across Hambleside Danelaw’s product range such as Zenon Rooflights and Dryseal, the unique flat roofing membrane system.