Calculate how much timber cladding you need for your wall, extension, garden room, outbuilding or other project. Enter your wall dimensions, subtract doors and windows, choose your cladding profile and allow for waste to estimate the number of boards and linear metres required.
Calculate How Much Cladding You Need
Use the calculator below to estimate your timber cladding requirements.
How Does a Timber Cladding Calculator Work?
A timber cladding calculator estimates how many cladding boards are required by working from the area of wall to be covered and the actual usable coverage of each board.
The important measurement is not always the nominal board width. Tongue and groove, shiplap and other overlapping profiles have an effective cover width, which is the amount of wall actually covered by each board once the joint or overlap is assembled.
The calculator therefore uses the effective cover width and board length to determine the approximate coverage of each board, then adds the selected waste allowance.
Wall area
Multiply the wall width by its height to calculate the gross area. If you have several walls, calculate each wall separately and add the areas together.
Doors and windows
Subtract the combined area of doors, windows and other openings from the gross wall area before calculating the cladding requirement.
Effective cover
The effective cover is the actual width of wall covered by each board. It is normally less than the nominal board width where boards overlap or interlock.
Waste allowance
Cladding needs to be cut around corners, openings and changes in wall dimensions. Allowing for waste helps avoid running short during installation.
Why Effective Cover Width Matters
One of the most common mistakes when estimating timber cladding is using the full board width rather than the manufacturer's effective cover width.
For example, a board with a nominal width of 125mm may not provide 125mm of installed coverage if part of that width is used for an overlap or tongue and groove connection.
Always check the finished or effective coverage dimensions for the exact cladding product you are buying.
Armstrong Timber Cladding Profiles
Armstrong supplies a range of timber cladding profiles and sizes, including tongue and groove, TGV and shiplap style boards. The exact effective cover depends on the product and finished dimensions.
| Cladding type | Typical characteristic | What to check |
|---|---|---|
| Tongue & Groove / TGV | Interlocking boards providing a consistent finished appearance | Effective cover width and finished thickness |
| Shiplap | Overlapping profile commonly used for external timber cladding | Finished width and overlap |
| Loglap | Profiled timber cladding with a more pronounced overlapping appearance | Effective cover width and board length |
How Much Timber Cladding Do I Need?
To calculate how much timber cladding you need, first measure the width and height of every wall that will be clad. Multiply these measurements together to calculate the gross wall area.
Next, measure your doors, windows and other openings and subtract their combined area. This gives you the net area that actually needs cladding.
Divide the net wall area by the coverage provided by each board. Finally, add a suitable allowance for waste and round the result up to a whole number of boards.
Example Timber Cladding Calculation
Imagine a wall measuring 8 metres wide and 2.5 metres high.
8m × 2.5m = 20m² gross wall area.
If doors and windows account for 4m², the net area requiring cladding is:
20m² − 4m² = 16m².
If the selected board has an effective cover width of 105mm and is 3.6m long, one board provides approximately:
0.105m × 3.6m = 0.378m².
The calculator then divides the net wall area by the board coverage and adds the selected waste allowance.
Board lengths, effective cover widths and usable coverage can vary between products. Always use the finished dimensions and manufacturer's coverage information for the exact profile you are purchasing.
How Much Waste Should I Allow for Timber Cladding?
Timber cladding normally requires some additional material for cutting, joints, corners, openings and damaged or unsuitable sections.
A 10% allowance is a useful general starting point for estimating, which is why the calculator uses 10% as its default. A more complicated project with many openings, angles or short sections may require a larger allowance.
Conversely, a simple rectangular wall with long uninterrupted runs may produce less cutting waste. The final allowance should therefore reflect the design and installation method.
Horizontal or Vertical Timber Cladding?
Timber cladding can be installed horizontally or vertically depending on the chosen profile, building design and installation system.
Horizontal cladding is commonly installed with boards running across the wall, while vertical cladding runs from the lower part of the wall upwards. The direction of the boards affects how joints, battens, corners and openings are detailed.
The calculator provides an area and coverage based estimate. For complex layouts, staggered joints or projects with numerous openings, a detailed cutting plan may produce a different final board quantity.
Timber Cladding for External Walls
Timber cladding can be used to change the appearance of house exteriors, extensions, garden rooms, garages, outbuildings and commercial buildings. Armstrong's external cladding range includes treated and untreated timber options in different profiles and sizes.
The correct cladding product should be selected according to the intended application, exposure, installation method, ventilation requirements and manufacturer's guidance.
What Goes Behind Timber Cladding?
External timber cladding is normally part of a wider wall build-up rather than simply being fixed directly to a wall. Depending on the construction, the system may include a suitable substrate, breather membrane, battens, ventilation cavity and appropriate fixings.
The exact build-up depends on the building construction and cladding system. Always follow the installation instructions for the product being used and ensure that the supporting structure is suitable.
Timber Cladding Calculator FAQs
How do I calculate how much timber cladding I need?
Multiply the width of each wall by its height to calculate the gross area. Subtract the area of doors and windows, then divide the net area by the installed coverage of the chosen cladding board. Finally, add an allowance for waste and round up to whole boards.
How many cladding boards do I need?
The number of boards depends on the wall area, board length and effective cover width. A longer board covers more area, while a wider board generally provides more coverage per board. The calculator above uses these measurements to estimate the required quantity.
What is effective cover width?
Effective cover width is the actual width of wall covered by a cladding board after accounting for the tongue and groove, overlap or other joint arrangement. It can therefore be smaller than the nominal board width.
What is the difference between nominal width and effective cover?
Nominal width is the stated overall width of the board. Effective cover is the usable width once boards are installed together. For overlapping and interlocking profiles, the effective cover is normally smaller than the nominal width.
How much waste should I allow for timber cladding?
Around 10% is a useful general allowance for many projects, although the correct figure depends on the wall design, number of openings, corners, board lengths and cutting requirements. More complicated projects may require a larger allowance.
Should I subtract windows and doors from the cladding calculation?
Yes. Enter the combined area of all doors and windows into the calculator so that this area is deducted from the total wall area.
Can I use this calculator for shiplap cladding?
Yes. Select shiplap and enter the actual effective cover width and board length for the product you are using. Shiplap boards overlap, so using the effective cover rather than the full nominal width is important.
Can I use this calculator for tongue and groove cladding?
Yes. Select TGV or tongue and groove and enter the effective cover width from the product specification. The tongue and groove connection means the installed coverage can be less than the overall board width.
Can I use the calculator for vertical cladding?
Yes. Select vertical orientation in the calculator. The underlying area calculation remains based on the wall area and effective board coverage, although the final cutting plan can vary depending on the wall dimensions and installation layout.
Is the timber cladding calculator accurate?
The calculator provides an estimate based on the measurements and product dimensions entered. Actual requirements can vary because of cutting, joints, corners, openings, board lengths, installation method and site conditions. Always check the manufacturer's product information before ordering.
Do I need battens behind timber cladding?
The supporting structure and ventilation arrangement depend on the construction and cladding system. External timber cladding is commonly installed as part of a ventilated wall build-up using battens, but the correct arrangement should be confirmed against the manufacturer's installation guidance and the specific building construction.
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