Entry 24 · Doors
Timber species for doors and windows: what the wood decides
Compare timber species used in replacement doors and windows, from durability and movement to finish, and learn what the wood choice decides.
When a quote for timber windows or doors names a wood, that name is doing real work: it sets the durability of the frame in British weather, how much the timber moves across the seasons, how well it takes and holds a finish, and what the unit weighs in the hand. Ask which species or which engineered material is offered, in writing, because timber is a family of very different answers rather than one material.
People who work wood at the lathe read a species the way a joiner reads a frame section, by grain, weight and behaviour under the tool. Vermont Woodturning Journal keeps wood species notes for the workshop, covering maple, cherry, walnut, oak and the other names a woodworker learns by handling them, and the same habit of reading the species rather than the label applies at the window order.
01 What does the species decide in a frame?
Four properties carry the decision. Durability is the timber's own resistance to rot and insect attack in damp conditions. Stability is how much it swells and shrinks as the seasons move, which is what keeps a casement closing square in February and August alike. Density sets the weight of the sash and the strength at joints and fixings. And grain decides how a finish sits and how the surface ages.
Those four trade against each other. A hard, durable species may move more or take paint unevenly; a stable softwood may need the finish to do the protecting. There is no single correct answer, only a correct match between species, exposure and finish, which is why the name on the quote deserves a line of questions rather than a nod.
02 Which names recur on quotes?
Engineered softwood, usually laminated redwood or pine, is the common base: stable, affordable and entirely dependent on its coating. Hardwoods like sapele and oak bring density and natural durability at a higher price and a heavier sash. Modified timbers, of which acetylated wood is the name you will meet most, trade natural chemistry for a treatment that changes durability and stability together.
Each name on a quote should come with its coating system, because the species and the finish are one answer, not two. Ask for the written specification of both, and ask what the maintenance cycle is on your elevations. A sheltered north face and a weather-beaten south bay ask different things of the same timber.
Engineered sections change the conversation again. Finger-jointed and laminated components take short, defect-prone lengths out of the frame and keep the stable heartwood where the joinery needs it, which is why a modern timber window often reads as a wood product engineered rather than a plank sawn. Ask where in the frame the engineered material sits and what shows on the surface, because a paint finish over engineered cores is a different proposition from a clear finish over solid oak.
03 How does finish change the answer?
Finish is the working skin of a timber frame. A factory-applied paint or stain, microporous so the wood can breathe, does the weatherproofing the species cannot do alone. End grain at joints and the bottoms of sashes is where water enters first, and a specification that seals and drains those points is worth more than an exotic species name on the headline.
Timber Development UK keeps reference material on timber species, durability classes and their uses for readers who want the underlying tables rather than a brochure summary. Read it alongside the quote and the species name stops being marketing and becomes a checkable property of the frame.
04 Where does the choice meet the survey?
The survey is where species stops being abstract. Exposure on each elevation, the condition of adjacent masonry, the weight an old opening can carry and the access for future recoating all feed the choice, and the entry on what a window survey records shows how those notes land on the order. A back door that meets dogs and weather together asks yet more of the timber, and the note on a back door for a household with dogs covers that side of the ledger.
Provenance is the last line worth asking about. Where the timber grew, how it was dried and whether the merchant can name the supply chain are not decorative questions, because a species bought on name alone can arrive greener or faster-grown than the name implies. The written answer sits comfortably beside the coating spec in the order file.
When the quote names a species, write down the name, the coating, the maintenance cycle and the durability claim, then compare like with like across the quotes you hold. The timber is the frame's first decision, and it is the one that keeps deciding for thirty years.
Species and finish settle how a door or window behaves over decades, but the fabric itself carries a record worth reading before any saw is set to it. Dating an old window follows the method a collector applies to an antique clock: the tool marks, the glass thickness, the hinge pattern and the sash weights are each compared against known periods, and restoration then turns on matching those parts rather than replacing them wholesale. Collectors often begin with one modest piece and learn its details first. The Sash and Frame Ledger sets out that approach in its entry on marks on an old window, useful when a timber survey precedes a decision.