Our timber firrings are tapered sections cut to order for flat roof construction, available in rise heights from 50mm to 200mm and lengths from 1.2m to 4.8m. Firring strips are laid across flat roof joists to create the fall required by building regulations, directing water towards outlets and preventing standing water. Order your required size online for fast UK delivery.
Timber firrings from Nottage Timber Merchants are sawn tapered sections for flat roof construction, cut to order in a range of rise heights and lengths. Used to create the correct drainage fall on flat roofs to meet building regulations. Order online for fast UK delivery.
Timber Firrings and Firring Strips for Flat Roofs
What Are Timber Firrings and How Do They Work?
Timber firrings, also known as firring strips or firring pieces, are tapered lengths of timber used in flat roof construction to create a drainage fall. Each piece is cut with a gradual taper along its length, thicker at one end and thinner at the other. When laid on top of flat roof joists, they introduce a consistent slope across the roof surface. This slope directs rainwater towards gutters, outlets or drains and prevents standing water, which is a common cause of flat roof failure. Firrings are fixed to the joists before the roof decking is laid on top.
Flat Roof Fall Requirements — What Size Firrings Do You Need?
Under BS 6229, flat roofs must be designed with a minimum fall of 1:40 to ensure a finished fall of at least 1:80 is achieved once construction tolerances are accounted for. To calculate the rise height required, divide your roof span in millimetres by 40. For a 4m span, this gives a required rise of 100mm over the length of the joist. Our firrings are available in rise heights of 50mm, 75mm, 100mm, 150mm and 200mm to suit different spans and fall requirements. If you are unsure which rise height you need, measure your joist span and divide by 40 to find the figure.
Our sawn timber firrings are cut to order, available in four standard lengths from 1.2m to 4.8m and five rise heights from 50mm to 200mm. This range of sizes covers the most common flat roof spans and fall requirements without needing to cut down larger sections on site. Orders are despatched quickly from our warehouse for fast delivery across the UK to trade and public customers. If you need a rise height or length outside our standard range, contact our team to discuss bespoke cutting options before placing your order.
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