Seeing the wood for the trees

Lucy Greenslade finds that doors really do grow on trees.

First let us be clear that we are talking about solid timber exterior doors; typically your front door, back door and garden doors. Veneered doors – where a thin skin of carefully selected fine timber is applied to a background of chipboard or cheap timber blocks – are something entirely different and merit a separate discussion. I am excluding veneered doors today because, although they make excellent internal doors, there are doubts about their long-term durability when exposed to the elements.

The difference between ‘hardwood’ and ‘softwood’ is botanical not practical. Describing a door as ‘made from hardwood’ is more a sales pitch than a reliable technical specification. ‘Hardwoods’ come from deciduous trees (which drop their leaves before winter) and ‘softwoods’ from ever-green conifers. That’s the difference.

The TRADA (Timber Research & Development Association) Product Directory lists about one hundred hardwoods that are suitable for joinery but not all are classed as ‘durable’ for exterior use. The alphabetical list runs from Abura and Afrormosia to Walnut and Wenge. TRADA also lists twenty-five softwoods, ranging from Cedar through Larch, Pines and Spruce to Yew. In theory a door could be manufactured in almost any of these but the practical experience of generations of joiners has determined the uses to which various timbers are best suited: Ash – furniture, Beech – cabinets and worktops, Cedar – cladding and decking, Elm – furniture and coffins, Douglas Fir – structural timbers, Hornbeam – chopping blocks and mallets and so on. Oak and Pine are versatile timbers and put to many uses, including the making of doors; but bear in mind that there are significant differences of price and durability between them.

Oak

In the past, good old Pitch Pine was the traditional choice of joiners for Georgian and Victorian front doors and windows. Nowadays good quality, bespoke, exterior doors are most commonly made from Meranti, Oak or, increasingly, Accoya. Meranti (sometimes known as ‘Philippine Mahogany’) is a hardwood originating in south-east Asia. It has a very dense cell structure and suffers relatively little shrinkage as it dries out. Meranti doors are more suitable for painting than for staining and varnishing. Oak is slow growing and slow-drying. Slow growth aids its durability over the faster-growing pines but Oak has a natural tendency to split and warp as its inevitable drying shrinkage causes stresses and movement. There are also significant differences in appearance and durability between European and American oaks.

Accoya

Accoya is a not a separate timber species at all but a high technology long life wood. It results from a process known as ‘acetylation’ whereby sustainably-sourced softwood is chemically modified to make it remarkably stable and durable. Although it sounds very scientific the Accoya production process is non-toxic and environmentally friendly. I found that Accoya was the twenty-first century timber of choice amongst carpenters and joiners for top-quality, painted, exterior doors.

www.accoya.com

Bespoke Front Door

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