Sawn Timber Firrings are designed to create a fall on flat roof systems, ensuring water drains away and preventing ponding. Typically, these timbers are fixed onto ceiling joists or roof structures to form the required slope. Despite the term “flat roof,” building regulations require a slight gradient to avoid water pooling.
Our flat roof firrings are cut to order, available in a range of standard heights and lengths (commonly 50mm, 100mm, and 150mm), and can also be manufactured to bespoke sizes to suit specific projects. For DIY or general building applications, “to 0mm” firrings are often used, where the timber slopes from a specified height at one end down to 0mm at the other.
Building Regulations Guidance:
-
Minimum fall recommended: 1:40
-
Minimum finished fall per BS6229: 1:80
-
Timber sizing is nominal; regularised timber typically finishes around 5mm smaller than stated (e.g., 50mm becomes 45mm). Falls are calculated based on finished units, not timber dimensions.
-
Example: For a 3600mm roof:
-
1:40 fall → 90mm drop required
-
1:80 fall → 45mm drop minimum
-
Firring heights can vary depending on roof specifications. A 100mm to 10mm firring may be specified to achieve a 90mm fall, instead of a “to 0mm” run. Always confirm requirements with the architect or roofing material manufacturer.
Key Features:
-
Creates a sloped fall for flat roofs to prevent ponding
-
Cut to order in standard or bespoke sizes
-
Suitable for DIY and professional building projects
-
Nominal sizes; finished size may be slightly smaller due to planing/regularisation
-
Compliance guidance provided with reference to BS6229 (check latest regulations for full accuracy)
Sawn Timber Firrings provide a reliable and easy-to-install solution for creating correct roof falls while allowing flexibility for bespoke requirements.
