Cladding Project Calculator

It depends on the profile. A 150mm PVC shiplap board (5m long) covers 0.75 m² — so for 10 m² of wall, you need approximately 14 boards (with 10% waste). A 100mm V-joint covers 0.5 m², doubling the board count. For timber, calculate using effective face width (board width minus tongue) — e.g. a 125mm shiplap covers 0.113m per linear metre.

Yes — almost always. Battens create a ventilated cavity between the cladding and the substrate, allowing moisture to escape and preventing rot. Standard spacing is 400mm for PVC and timber, and 600mm for cement-fibre on rigid substrates. Use 38×25mm treated softwood for PVC, 50×25mm for timber, and 50×38mm for cement-fibre.

For external cladding on a habitable building, yes. A breather membrane (vapour-permeable) lets internal moisture escape outwards while keeping wind-driven rain from reaching the substrate. It is required under Building Regulations Approved Document C for new builds and recommended for any retrofit cladding installation. Skip only for outbuildings or shelters where weather penetration is not a concern.

10% is standard for straightforward elevations with rectangular shape and few openings. Increase to 15% for complex walls with many cuts (windows, doors, dormers, gable ends), angled board layouts, or when using long boards on short walls where offcuts cannot easily be reused. For premium materials (larch, cedar, cement-fibre), waste planning is more important because offcuts have higher unit cost.

For most domestic properties, re-cladding is permitted development as long as the materials are of similar appearance to those on the existing house. Planning permission is required for listed buildings, properties in Conservation Areas, AONBs, National Parks or World Heritage Sites, and for any building over 18m where Building Regulations now require non-combustible materials (A2-s1, d0 minimum). Always check with your local planning authority before starting.

For low maintenance and longest lifespan, cement-fibre (Hardie Plank) is hard to beat — 40+ year lifespan, A2 fire-rated, no rot or fading. PVC is the cheapest low-maintenance option (10-year colour guarantee, no painting) but combustible (D-s3, d2). Timber gives the most natural finish but needs re-staining every 5–10 years; Siberian larch and Western red cedar are naturally durable and silver gracefully if left untreated. Choose based on budget, maintenance tolerance and aesthetic preference.