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Fascia Board Calculator — Boards, Trims & Fixings
Calculate fascia boards needed for your roof perimeter. Includes corner trims, joining pieces and fixing screws.
Total eaves perimeter (sum of all sides)
Splits the perimeter into runs (boards can’t span a corner). Typical house: 4
Foiled boards expand more, so fix at 400mm centres instead of 600mm
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How We Calculate This
A roof perimeter is broken into separate eaves runs at each corner, because a fascia board is cut and finished at a corner trim rather than bending around it. So boards are counted per run — each run rounded up on its own — and the runs are added together. Dividing the whole perimeter by one board length is only a lower bound.
The method
- Runs: the perimeter is split into runs (one per corner) of roughly equal length.
- Boards: each run = ⌈run length ÷ board length⌉; sum across all runs.
- Corner trims: one per corner.
- In-line joint trims: boards − runs (joints within a run only — corners use corner trims).
- Fixings: 2 per centre at max 600mm (white) or 400mm (foiled) centres.
Runs are assumed equal in length; for an exact count, measure each side and round it up individually. Fixing centres follow uPVC fascia manufacturer fitting guidance (e.g. Eurocell, Deeplas).
Frequently Asked Questions
Count the boards for each side (run) of the roof separately, because a fascia board cannot wrap around a corner — it is cut and finished at a corner trim. For each run, divide the run length by the board length and round up, then add the runs together. For example, a square house with 24m of eaves is four 6m sides; with 5m boards that is 4 × 2 = 8 boards, not 5. Simply dividing the whole perimeter by the board length (24 ÷ 5 = 5) gives a lower bound only and will leave you short.
UK uPVC fascia boards are most commonly stocked in 2.5m and 5m lengths (some suppliers also offer 3m). 5m boards reduce the number of in-line joints on long runs. Foiled or coloured boards are often supplied or fitted in shorter lengths because they expand more than white.
Fix at the rafter ends with 2 fixings per fixing point at a maximum of 600mm centres for white uPVC, reduced to 400mm centres for foiled or coloured boards (which absorb more heat and expand more). Use 65mm A4 stainless steel polytop nails or 65 × 4mm stainless screws. Leave a 5mm expansion gap at each board end, covered by a joint or corner trim.
The width depends on the depth of your rafter feet. Common UK sizes are 150mm, 175mm, 200mm and 225mm. Measure your existing fascia or rafter ends to determine the correct width.
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Last updated: March 2026
Verified against UK standards · estimates only, confirm with your supplier.