Timber Cladding Calculator: How Much Do You Need?

Start with installed cover, not nominal board width

The most important input is the installed cover of the selected profile. This is the visible width or height contributed by each board after overlaps, tongues or joints are engaged. It is often smaller than the overall machined width, so calculating from the nominal board size can understate the quantity required.

Use the supplier's current profile drawing to confirm finished dimensions and installed cover. Two products both described as shiplap, shadow gap or tongue-and-groove may have different joint depths and coverage. The calculation should be updated if the profile or finished dimensions change.

If a product has not yet been selected, measure the elevations first but treat the result as provisional. Keep the raw dimensions so alternative species and profiles can be compared without repeating the site survey.

• Finished board width and thickness
• Installed cover after joint engagement
• Available board lengths
• Vertical or horizontal orientation
• Profile-specific fixing and support requirements

Measure each elevation separately

Draw or obtain an elevation for every wall or cladding zone. Record width and height in consistent units, then divide irregular façades into simple rectangles and triangles. Calculate each shape separately before combining the totals. This makes the working easier to check and preserves information about where the area occurs.

Do not combine every wall into one anonymous square-metre figure. A long, low elevation may use board lengths efficiently, while a narrow gable with several openings can create more cuts and joints. Separate measurements allow the supplier to consider those differences.

Label each zone by orientation and location, such as front vertical cedar, rear horizontal larch or entrance coated redwood. This is particularly useful where more than one species, profile or finish appears on the building.

Handle windows and doors carefully

Large openings can be deducted from the main wall area, but the reveals, heads and sills around them may still require boards, trims or another finish. Small openings do not always reduce the order by their full area because cutting around them can create short pieces that cannot be reused elsewhere.

Measure the opening itself and record the depth and proposed finish of each reveal. Mark whether boards continue into the reveal, stop at a metal trim or meet a different material. The quotation can then include the correct components instead of assuming every opening is a simple deduction.

Where identical windows repeat, confirm that their dimensions and surrounding details are genuinely the same. Construction drawings can make openings look consistent even when site conditions or trim choices differ.

Convert wall measurements into board quantities

For area planning, multiply the width by the height of each rectangular zone. For a simple triangular gable, use half of the base multiplied by the vertical height of the triangle. Add the relevant shapes, then adjust for openings and details using the agreed scope.

To estimate linear metres, divide the net cladding area by the installed cover expressed in metres. For example, the calculation is net area divided by installed cover, not net area divided by the full board width. The result represents the combined length of board faces required before cutting and project allowances are considered.

To estimate the number of boards, divide the required linear metres by the selected board length. Always round up to complete boards or packs, and remember that a mathematical total does not prove that every cut can be used efficiently on the actual elevations.

• Rectangle: width × height
• Triangle: base × height ÷ 2
• Linear metres: net area ÷ installed cover in metres
• Board count: linear metres ÷ selected board length
• Round up to the supplier's complete-board or pack quantity

Board lengths and joints can change the order

Available lengths should be compared with the elevation before the final quantity is set. A board that spans a complete course or height can reduce joints, but may be harder to handle or deliver. Shorter lengths can be efficient when openings create natural breaks, provided every joint lands on suitable support.

Create a simple cutting plan for prominent walls. Mark proposed board ends, repeated window positions and any areas where short offcuts could be reused. Do not assume every remainder is usable: the piece still needs adequate length, sound ends and the correct profile orientation for its next location.

Where random lengths are offered, ask how the pack is composed and whether the quotation assumes a particular distribution. Where fixed lengths are offered, check that the building set-out has been coordinated with them.

Allow for vertical and horizontal layouts

Vertical cladding quantities are strongly affected by wall height, gables and the positions of horizontal openings. A board may run from base to roof on a simple elevation, while a window can divide the same board line into several pieces. The cutting plan should follow the exact façade rather than an average height.

Horizontal cladding is influenced by course length and the location of vertical joints. Long elevations may require joints even when the board is supplied in generous lengths. Decide whether joints align, stagger or fall at designed breaks, then make sure the batten layout supports them.

Board-on-board and feather-edge arrangements also use overlap that affects coverage. Shadow-gap and tongue-and-groove profiles have their own installed dimensions. Use the drawing for the precise product rather than transferring coverage from a visually similar board.

Choose a sensible project allowance

A final order normally needs an allowance for cutting, selection, damage and unavoidable offcuts, but one percentage is not responsible for every project. A plain rectangular wall with coordinated board lengths behaves differently from a gable-heavy house with many openings, corners and short returns.

Consider profile, grade, board direction, fixed or random lengths, joint strategy and the opportunity to reuse offcuts. Character grades may also require agreement about how visual selection is handled. Record the reasoning behind the allowance rather than adding an unexplained figure to the area.

The supplier or installer can review the drawings and proposed cutting plan before the order is confirmed. For complex elevations, that review is more valuable than relying on a calculator that knows only total square metres.

Include battens, fixings, trims and finish

Boards are not the complete material schedule. Battens and counter-battens depend on the wall design, board orientation, support centres and details around openings. Their lengths and junctions should be measured from the coordinated elevation and section drawings.

Fixing quantities depend on the number of support lines, board arrangement and chosen fixing method. Visible screws, nails and proprietary concealed systems are not interchangeable. Ask for product-specific guidance and include the relevant fixing material for the timber, treatment and site exposure.

Corners, starter pieces, upper terminations, ventilation components, membranes, flashings and finishing products may also be needed. Some items are measured in linear metres, some by unit and others by coverage. List them separately so they do not disappear inside the board calculation.

Check delivery, storage and South West exposure

Long boards require suitable delivery access, unloading space and protected storage. A length that looks efficient on the elevation may be impractical if it cannot reach the site or be moved safely to the installation area. Share access restrictions before the quotation is finalised.

Keep boards supported, dry and protected in accordance with supplier guidance. Poor storage can create damage or distortion that undermines an otherwise careful quantity plan. Confirm who will inspect packs on delivery and how discrepancies will be recorded.

For exposed projects in Devon, Cornwall, Somerset or around the Bristol Channel, provide the postcode, orientation and proximity to the coast. Site exposure may affect the product, finish, fixing and detailing discussion even though it does not change the basic measuring formula.

What to send with a cladding quotation request

Send dimensioned elevations rather than only the final area. Mark every cladding zone, opening, gable, corner and material transition. Identify the preferred species, grade, profile, finish, board direction and any lengths already considered.

Ask the quotation to show installed cover, board dimensions, lengths, quantity, pack basis, battens, fixings, trims, finish and delivery. This makes it possible to compare proposals on the same scope and spot where one supplier has included components that another has omitted.

The Cladding Centre can review drawings for homes, extensions, outbuildings and commercial façades across the South West. Send the project information through the quote page for a product-specific quantity review rather than relying on an isolated calculator total.

• Project postcode and delivery access
• Dimensioned elevations
• Openings, gables and returns
• Species, grade and profile
• Installed cover and preferred board lengths
• Vertical or horizontal orientation
• Required battens, fixings, trims and finish