redland recommendations
Although cold pitched roofs are by far the most common type of pitched roof in the UK - representing about 90% of all housing stock - in modern housing, as well as loft conversions to existing houses, there is an increasing trend toward using the roof space as additional living space. These changes in roof construction have implications for the most effective means of controlling the risks of harmful roof condensation. In what follows we summarise our recommendations - based upon the British Standard, BS5250 - depending on the choice of Redland roof covering product, and roof construction.
redland Slate, Plain Tile and Profile Range
All of Redland's slates/tiles in the Slate, Plain Tile and Profile Range are classified as "air-open" as defined in the British Standard. The Solution Finder below (Image 1 - Click to Download) summarises Redland's recommendations for when these products are used with Redland's Spirtech 100 and 250 VPU's in various roof constructions with standard rafters and no timber sarking boards (this covers most types of roofs constructed in England and Wales especially). The Solution Finders provide the amounts of additional ventilation recommended, expressed in continuous mm of gap both at low and/or high level (typically either 5 mm, 10 mm or 25 mm). Redland provides a wide range of roof ventilation products for the eaves and ridge, as well as ventilation tiles that can be used to provide the required amounts of additional ventilation both at low level and high level.
In the Solution Finder you will see Redland's recommendation for a cold pitched roof with a well sealed ceiling matches the solution the NHBC now recommend for this roof construction (see Image 2 below). Redland has always recommended the use of high level ventilation to minimise the risk of condensation in cold roof voids such as these - especially in new build dwellings where the moisture levels are high.
In parts of Scotland and more wind-exposed areas of the UK, it is common practice to cover timber rafters with timber sarking boards which can be either sawn planks with gaps in between, or larger boards with no gaps, termed sheet sarking. The Solution Finder below (Image 3 - Click to Download) summarises our recommendations for these types of roof construction. Where timber sarking is used, counterbattens are required in order to achieve the necessary drainage path to the eaves gutter between the roof covering and the underlay.
Redland Metal Range
Redland's range of Metal Roofing Sheets are classified as "air-tight" as defined in the British Standard. The final Solution Finder below (Image 4 - Click to Download) summarises our recommendations for when these products are used with Spirtech 100 and 250 VPU's in various roof constructions with standard rafters and no timber sarking boards. Again the recommendations are expressed in continuous mm of gap both at low and/or high level. Redland provide a wide range of ventilation products for use with our Redland Metal Sheet Roofing products.
For more information on the range of Redland products available to provide roof space ventilation for your project, it is advisable to contact Redland Technical Solutions on Tel. 08708 702595. Redland can also provide a free of charge guaranteed design specification via our SpecMaster service.