Quickly estimate the amount of exterior hardwood cladding and fixings you need with our easy-to-use Exterior Cladding Calculator. Get precise results in both square and lineal metres delivered directly to your email. Please remember to add 10-15% wastage to your calculation for offcuts etc.
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To work out how much exterior cladding you’ll need, start by measuring the wall area in square metres—multiply the height by the width, then subtract the area of large windows or doors. The profile you choose affects how much timber is required, as each one has a different cover width (the visible portion once installed).
It’s standard practice to allow an extra 10–15% to account for cuts and waste.
For a quick estimate, you can use our online calculator. If you’re working from building plans or a more detailed design, we also offer a free quantity surveying service—we’ll do a take-off and provide you with estimated material quantities.
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Board width is the full size of the timber plank, while cover width is how much of it is visible after installation, taking overlaps or rebates into account. For instance, a 140mm wide board would offer 115mm of cover. Our calculator uses the actual cover widths of each cladding profile to give you a more accurate material estimate. If you’re not sure which profile to select, our team can guide you through the options based on your design and fixings.
Durable Class 1 hardwoods – both reclaimed and sustainably like Spotted Gum, Ironbark, Tallowwood and Blackbutt perform exceptionally well in New Zealand’s weather conditions. These timbers offer natural resistance to moisture, rot, and UV exposure.
You can opt for lesser durable timbers like Cedar, Abodo, Larch, Lunar Wood etc which are all class 2 (15-40 years natural durability) and require extensive maintenance to meet their warranty needs. The class 1 hardwoods only require the minimum maintenance of washing them down once a year.
LMA Timber specialises in architectural-grade, sustainably sourced hardwoods, and we can advise you on which species are in stock and suitable for your climate zone.
The number of fixings depends on the profile, board orientation (vertical or horizontal), and cavity system. A general estimate on a standard 115mm cover board is approx. 17 fixings per square metre. When you use our calculator, just select your fixing method and cavity setup — we’ll provide an estimate based on your configuration. If you’re unsure which fixing type is best for your project, we can supply specs or recommend options suited to your cladding system.
Yes, in most cases the NZ Building Code requires a ventilated cavity system behind exterior cladding to manage moisture and prolong the life of the structure. The depth and type of cavity can depend on wind zone, building wrap, and profile choice. Our calculator includes common fixing and cavity combinations, and we can also provide technical information to ensure your system meets compliance and performs well in the long term.
Yes, the calculator is set up to work with both vertical and horizontal profiles. It calculates based on cover width, so whether you’re using vertical shiplap, weatherboards, or another profile, the estimate will reflect your selected option. If you’re unsure whether your profile is compatible with vertical or horizontal installation, we can confirm that for you and supply profile drawings if needed.
If you are replacing like for like then you will not require a building consent but please check with your local council for final approval. If you are completely changing the cladding type on the exterior of your home then you will require consent because it changes the building envelope typology. The requirements vary by council and depend on whether you’re altering the structure or insulation values. We can provide product specs, durability ratings, and installation documents to help with your consent application or to share with your architect or builder.
This is one of the most frequently asked questions—we hear it four to five times a day. In New Zealand, we follow the Australian standard for timber durability classification, which divides timber into four classes:
Class 1 – Very durable: 40+ years
Class 2 – Durable: 15–40 years
Class 3 – Moderately durable: 7–15 years
Class 4 – Non-durable: 0–7 years
Around 90% of claddings used in New Zealand are Class 2 softwoods such as cedar, Abodo, larch, and Weathertex. These typically require high levels of maintenance to meet warranty conditions.
In contrast, our Australian hardwoods are Class 1, offering over 40 years of durability when installed according to the building code—with minimal maintenance. A simple annual washdown is usually sufficient. If you choose to oil your cladding every few years, its lifespan can extend well beyond 100 years.
Thanks to their high density (a cubic metre of Spotted Gum or Ironbark is heavier than a cubic metre of concrete!), these timbers offer excellent wear resistance. They may develop surface checking and naturally weather to grey over time—just like we do—but their structural performance remains uncompromised for decades.
Dense species like Ironbark and Spotted Gum are also highly resistant to decay and insect attack, especially when installed with a well-ventilated cavity. If you’d like to maintain the original colour of your cladding, applying a UV-inhibiting tinted oil is recommended, based on the level of sun exposure.
Yes, LMA Timber delivers to residential and commercial sites across New Zealand with our main warehouse being in Christchurch. Delivery timeframes depend on the hardwood product you require – most claddings and decking we hold in stock. More custom items like beams / posts need to be milled in Australia with a lead time of around 8-10 weeks.
After using the calculator to estimate your quantities, please get in touch with us to confirm lead times and supply availability — we’ll do our best to make sure your cladding or decking arrives when you need it.
