Free UK construction calculators Metric and imperial 2026 UK prices
Work out how much cladding you need for a house, extension, garage or garden room. Enter the wall size, any gable, windows and doors, then press Calculate to see the boards, battens, breather membrane, fixings and cost for timber shiplap, fibre cement or composite cladding.
| Cladding | Boards | Battens | Materials | Per m² |
|---|
Boards, battens and membrane for the same walls, each at its usual batten spacing. Your choice is highlighted.
The result gives the number of boards or lengths, the battens, breather membrane rolls, fixings and corner trims, with the cost of each and the total per square metre. A table compares the three cladding types for the same walls, and the drawing shows your wall with the board lines and battens to scale.
Measure each wall along the bottom, from corner to corner, and add the lengths together. Measure the height from where the cladding will start (normally at least 150 mm above the ground or the damp-proof course) up to the underside of the soffit or eaves.
A gable is the triangle above the eaves at the end of a pitched roof. Its area is half the width times the height, so a gable 6 m wide and 2 m high adds 6 m². The calculator takes off 1.44 m² for each window (1.2 × 1.2 m) and 2.1 m² for each door (1.0 × 2.1 m). If your openings are much bigger, such as bifold doors, count them as two or three doors. It is always better to have a few boards left over than to run short, because a later batch may not match in colour.
| Cladding | Typical board | Cover per board | Upkeep | Fire |
|---|---|---|---|---|
| Timber shiplap | 19 × 125 mm treated softwood | About 105 mm (9.5 m per m²) | Re-stain every 3 to 5 years | Combustible |
| Fibre cement lap | 3.6 m × 190 mm × 10 mm | 160 mm (0.576 m² per board) | Pre-painted, wash down | A2 (non-combustible) |
| Composite | 3.6 m × 157 mm | About 125 mm (0.45 m² per board) | No painting, may fade at first | Combustible |
Timber is the cheapest and easiest to work, and suits sheds, garden rooms and rural buildings. Treated softwood needs a stain or paint to keep it looking good; larch and cedar can be left to weather silver. Fibre cement boards look like painted timber but do not rot, and are a safe choice near boundaries because they do not burn. Composite boards are made from wood fibre and plastic, need no painting and clip on with hidden fixings, but cost the most and must be fixed with expansion gaps.
The key figure is the cover width: how much of each board shows once it is lapped over or locked into the board below. It is always less than the board width. Divide 1 by the cover width in metres to get the metres of board per square metre, then divide by the board length.
| Cladding | Boards | Battens (4.8 m) | Fixings | Materials |
|---|---|---|---|---|
| Timber shiplap | 53 × 4.8 m | 10 at 600 mm | About 420 | £943 |
| Fibre cement lap | 46 × 3.6 m | 10 at 600 mm | About 275 | £992 |
| Composite | 59 × 3.6 m | 14 at 400 mm | About 530 | £1,288 |
Fibre cement needs fewer boards because each one covers 160 mm. Composite needs more battens because most makers ask for 400 mm centres. Joints between board ends should land on a batten, and are best staggered so they do not line up up the wall.
Cladding is a rainscreen: some water will get behind it, so it needs a ventilated, drained gap. Fix a breather membrane to the wall or timber frame, then vertical treated battens (usually 50 × 25 mm or 50 × 38 mm) at 400 or 600 mm centres to hold the boards off the wall. Fit extra battens each side of every window and door so the board ends are fixed.
Using typical 2026 UK merchant prices including VAT, the materials for boards, battens and membrane come to roughly:
| Cladding | Board price used | Materials per m² |
|---|---|---|
| Timber shiplap | £3.25 a metre (£15.60 for 4.8 m) | About £38 to £45 |
| Fibre cement lap | About £19 a 3.6 m board | About £40 to £48 |
| Composite | About £19.50 a 3.6 m board | About £53 to £61 |
Small jobs cost more per square metre because you still have to buy a whole roll of membrane. Trims, fixings, stain and delivery are extra, and premium products such as cedar, larch or branded composite systems can cost two or three times as much. A builder will also charge for labour and scaffolding.
Re-cladding a large part of an outside wall can count as renovating a thermal element under the Building Regulations, and new cladding on an extension is part of the building work. Approved Document B limits combustible cladding on a house wall within 1 m of a boundary (it must be class B-s3,d2 or better), and residential buildings with a storey 11 m or more above the ground need non-combustible materials in the external walls. Fibre cement rated A2 is usually accepted in these places; timber and composite often are not. Planning permission may also be needed to change the look of a house in a conservation area or on a listed building, so check with your council before you start.
Wall area = length × height + gables × ½ × width × height
Area to clad = wall area − windows × 1.44 m² − doors × 2.1 m²
Boards = area to clad × (1 + extra) ÷ (cover width × board length), rounded up
Battens = (wall area ÷ spacing + 2 × opening heights) × 1.10 ÷ 4.8 m · Membrane = wall area × 1.10 ÷ 75 m²
Fixings = area to clad ÷ (cover width × spacing) × 1.10 · Corner trims = corners × wall height
The membrane and battens go over the whole wall, while the boards are only needed where there is no window or door. The figures are estimates for ordering; always check the cover width and fixing rules in the maker's guide.
Multiply the wall length by its height, add any gables (half the width × height), take off the windows and doors, and add 10 to 15% for cutting. Divide by the area each board covers.
For 19 × 125 mm shiplap with a cover of about 105 mm, about 9.5 metres per square metre, before adding for cutting.
A Cedral Lap board is 3.6 m long and covers 160 mm once lapped, so 0.576 m² a board, or about 1.75 boards per m².
Usually 600 mm centres for timber and fibre cement, and 400 mm for most composite cladding. Use closer centres on exposed sites and always follow the maker's guide.
Yes on a timber frame or a wall that needs protecting from rain. It keeps wind-driven rain out while letting water vapour escape, and goes behind the battens.
Treated softwood shiplap is the cheapest at about £3.25 a metre. Fibre cement costs a little more overall and composite cladding the most.
Within 1 m of a boundary, house walls generally need cladding of limited combustibility, such as A2 fibre cement. Timber and composite are often not allowed there.
Shiplap and lap boards are fixed horizontally on vertical battens. Vertical cladding needs horizontal battens with counter-battens behind, so air and water can still drain.
Board sizes from Cedral Lap (3600 × 190 mm, 160 mm cover), merchant data for 19 × 125 mm shiplap (about 9.5 m per m²) and Cladco composite cladding (0.45 m² per board). Battens 50 × 25 mm × 4.8 m; breather membrane 1.5 × 50 m. Typical 2026 UK prices including VAT. Fire limits from Approved Document B. Reviewed November 2026.