Advanced options
Cover width is the board width minus the overlap/rebate: it's what each board actually adds up the wall, and it's the number merchants quote. Cladding hangs on treated battens (add roughly 2 linear metres of batten per m2 at 400-600mm centres) over a breather membrane, with stainless or ring-shank nails: standard nails streak rust down timber within a season.
What The Cladding Calculator Works Out
- Net area: the gross wall area minus windows and doors. Measure the wall to the full height including any gable triangle (half base x height) and take off the openings.
- Linear metres: net area divided by the board's cover width, plus a wastage allowance (10% by default) for mitres, offcuts and the one twisted board. Cover width is the face minus the overlap or rebate: a 150mm shiplap covering 130mm turns every square metre of wall into 7.7 linear metres of timber.
- Boards to buy: the linear metres divided by the stock length (4.2m by default), rounded up. Featheredge covers less per board than shiplap's machined rebate, which is why the cheaper profile does not always give the cheaper wall.
- Custom cover width and wastage (advanced): type the exact cover width from the merchant's datasheet and set your own wastage. Walls with many openings or diagonal cuts want 15%; one plain gable can get away with 5%.
- Board length (advanced): UK cladding comes in 3.0m to 5.1m lengths. Longer boards mean fewer joints but more offcut on short walls; choose the length nearest a multiple of your wall width.
- Battens (advanced): treated 25 x 50 battens at your chosen centres, with the wall area divided by the spacing to give linear metres. Vertical boards need counter-battens as a second layer so the cavity still drains, which roughly doubles the batten order.
- Fixings (advanced): two nails per board at every batten crossing, with 10% spare and a 250-pack count. Use stainless or ring-shank galvanised: ordinary nails write rust streaks down every board within a season.
- Breather membrane (advanced): the net area plus 10% for the 100mm laps. It sheds wind-driven rain while letting the wall breathe, and insect mesh should close the cavity top and bottom.
- Board cost (advanced): boards x length x your price per linear metre, with a cost per square metre of wall. Treated softwood shiplap is typically GBP 2.50 to GBP 4.50 per metre, larch and thermally modified pine mid-table, cedar GBP 8 to GBP 14.
- Profile comparison table (advanced): the same wall priced in featheredge, three shiplap widths, tongue-and-groove and open-gap boards, plus the batten total, so you can see what the profile choice does to the order before committing. Cladding a house in a conservation area can need planning permission; sheds and garden offices do not.