Roofing and Ventilation - Technical Information

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GRP Valleys - why Hambleside Danelaw is the market leader.

There are alternative GRP valleys available within the UK market, Hambleside's range has been developed to meet fully the requirements of the NFRC Technical Bulletin TB28 which is now referenced in BS 5534:2003. In order to meet this Standard the production process does requires greater raw material usage during manufacture, but this results in a high quality long life product.

TB28 came into being as a result of collaboration between roofing consultants, roofing product manufacturers and roofing contractors due to a lack of clear, universally accepted guidelines on the design and installation requirements for ‘open’ pre-formed GRP valley troughs.  There were no British or European Standards covering these products until the document became referenced in BS 5534:2003 ‘Code of practice for slating and tiling (including shingles)’ when it was revised and updated during 2003, thus making it the only industry ‘standard’.

The NFRC document is based upon the requirements contained in BS 5534 for open valleys formed on site, in such materials as lead, and set out to provide guidance on how a pre-formed product should accommodate variable dimensional criteria encountered on different installations for a maximum design rainfall rate of 225mm/hr. 

TB28 defines the scope of use for two nominal valley widths, determined as ‘Standard’ and ‘Narrow’, based upon roof pitch and roof drainage area.  A valley trough centreline to margin width or ‘leg length’ is pre-determined for either mortar bedded tile valleys or dry fixed slate valleys for each of the two classifications. In addition, the outer fixing flanges of the valley troughs should be designed to fit over a counterbatten of the same thickness as the slating and tiling battens, now extensively 25mm thick, with the valley base or sole still being adequately supported by the valley boards. The mortar bonding strips used on tile valleys, which naturally need be sound and well adhered, should now be a minimum of 35mm wide to promote good mortar adhesion and integrity.

To view each of the product sections please use the links below:

Eaves & Soffit Ventilators | Eaves Panel Ventilators | Slate Roof Ventilators | Tile Roof Ventilators | Cavity & Underfloor Ventilators | StormForce 225 Valley Troughs | Dry Fix Valley Troughs | Continuous Dry Soakers | Individual Dry Soakers | Dry Verges | Dry Fix Bonding Gutters | Bonding Gutters | Miscellaneous Products