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Mind the gap for the perfect roofline installation

uPVC, of more correctly PVC-UE, makes for a great roofline material: It’s easy to cut and fix for the installer and delivers a long-lasting, low-maintenance product for the householder.

To ensure that uPVC roofline products are fitted correctly first time, and minimise the risk of callbacks, it’s important to allow for expansion caused by changes in temperature. For this reason, Kestrel recommends a 5mm gap for each white, 5m fascia board end and that joint trims are fixed to only one board.  

When fixing foiled or coloured products, the expansion gap should increase as darker uPVC absorbs more heat from the sun than white, leading to greater expansion. For foiled uPVC products, we recommend an 8mm expansion gap per board end.

Here are some further tips to ensure you deliver a first rate installation:

·  Joint trims should only be positively fixed to one board end to allow expansion gap movement.

·  It is recommended that joint trims should be fixed using low modulus neutral cure silicon, to allow for expansion and contraction.

·  Hold joint trims in place with medium tack tape (electrical insulation tape) until the silicone cures (or ‘skins’).

·  Fascia boards should be fixed in place with two polytop nails per fixing centre at a maximum of 600mm centre.

·  Ensure that polytop nails are made of austenitic stainless steel (grade A4 BS EN ISO 3506-1: 2009).

·  For a full replacement fascia (16mm+), use 65mm x 4mm polytop nails.

·  For a capping fascia (8 – 15mm) use 50mm x 4mm polytop nails.

·  Spread fascia fixings along the installation to utilise the full height of the rafter end.

·  Do not put pencil lines directly onto PVC as these will be very difficult to remove, instead use dots to mark nailing points.

·  Remove protective tape before nailing the boards in place to prevent trapping tape behind the nail heads.

·  Use standard round nails for tacking or positioning purposes prior to final fixing with polytop Nails as round nails are easily removed.

Kestrel has a range of technical guides for installers on its website. To view the guides go to http://www.kbp.co.uk/en/technical-literature and click on ‘technical bulletins’.