The main material we use for our exterior joinery is engineered Accoya (https://www.accoya.com/) – a modified softwood and by far the best material for windows and doors in the UK’s damp temperate climate. All normal timbers absorb and lose moisture as the humidity changes, expanding and contracting, stretching and shrinking the paint and massively reducing its lifespan. Accoya is different as it is dimensionally stable, not changing shape at all, so the paint lasts considerably longer – often over 25 years before repainting is needed – and even then, if the timber is exposed to the elements, it won’t rot, so redecoration is needed for aesthetic reasons rather than to protect the wood and increase longevity. Therefore, although a premium product, when the cost of repainting is considered, it works out to be a very economical method of manufacturing exterior joinery.

We also use engineered Sapele for doorsills and any lock stiles where hardware is to be fitted into the timber. For sills, because Sapele is a dense hardwood, so will handle the wear and tear of footfall better than Accoya. The acetylation process the Accoya goes through leaves acetic acid in the wood, which, whilst making it totally inedible to all wood boring insects and fungi, corrodes any steel (apart from stainless steel) in components. Although some fully corrosion-proof hardware is available, it is limited and very expensive. By using engineered Sapele for these components it allows for the installation of any hardware the customer desires, without any ill effect.

As a more economical method of acquiring joinery made to our high specifications and standards we can replace much of the Accoya with Western Red Cedar. This is the timber of choice for exterior joinery in North America and is naturally extremely rot proof, being used, untreated, for the manufacture of beehives, lasting for decades. We still recommend using Accoya for the horizontal rails of windows and the windowsills, and Sapele for doorsills. However, although a good cost saving will be made by using Cedar in this way, the joinery will have to be redecorated more frequently than if Accoya is used.