Elm

• European
  
• Wych

Elm Burr

The following information is posted with permission of Timber Research and Development Association (TRADA) and is taken from their red booklets Timbers of the World. © TRADA

European Elm

Ulmus spp.                         Family: Ulmaceae

Various species of the genus Ulmus occur in Europe, western Asia, North America and Japan. The following are those whose timber is found in Europe.
Ulmus procera Salisb. produces the English elm found mainly in England and Wales.
Ulmus hollandica Mill. var hollandica Rehd. produces Dutch elm found throughout the British Isles, and introduced from the Netherlands.
U. laevis Pall. produces European white elm found from Central Europe to western Asia.
U. carpinifolia Gleditsch. (U. nitens Moench U. foliacea Gilib.) produces smooth-leaved elm found in Europe including Britain.
U. stricta Lindl. produces the Cornish elm found not only in the west of England but also in Brittany.
U. glabra Huds. produces the wych elm of northern Europe including Britain.

English and Dutch elm are similar in their general characteristics. The trees grow to a height of 36m to 45m and a diameter as great as 2.5m but since large-diameter trees are frequently unsound in the centre, a diameter of 1m or slightly more is better commercially.

The timber
The heartwood is a dull brown colour, clearly defined when green from the lighter-coloured sapwood. The irregular growth rings together with the cross-grained character of the wood gives it an attractive appearance, but the large early-wood pores produce a rather coarse texture. The timber of these species when grown on the Continent is generally of more even and uniform growth with straighter grain. English elm weighs about 560 kg/m3 and Dutch elm about 580 kg/rn3 when dried.

Drying
Although releasing its moisture fairly rapidly, there is a very marked tendency for the wood to distort, and there is some liability for collapse to occur in thick sizes. Care is therefore needed; sticks should be properly aligned, and tops of piles weighted down.

Strength
Both English and Dutch elm have similar strength properties, and in general are some 30 per cent below the strength of oak, although Dutch elm is appreciably tougher than English elm, and it is also a much better wood for bending.

Durability
Non - durable.

Working qualities
Elm is basically a fairly difficult timber to work, tending to pick up during planing and moulding, and to bind on the saw. Its working properties are however governed to an extent by the care with which it was dried, distorted wood being wasteful in planing and moulding. Dutch elm is not quite as refractory, but both species can be finished to a clean surface with care. The wood can be glued satisfactorily, and can be stained, polished or waxed. It takes nails without splitting, and can produce a good decorative veneer.

Uses
The attractive grain in elm renders it ideal for furniture, turnery and woodware such as salad bowls. It is used for chair seats, bent-wood backs, coffins and for domestic flooring. It is a good timber for use in boats for transoms and rudders, hatch covers, bottom planks etc, and is used in dock and harbour work for fenders, rubbers, keel-blocks, capping, wedges and for construction.

Wych elm

The wych elm attains a height of 30m to 38m and on favourable sites produces a bole of about 12m in length and a diameter up to 1.5m.

The timber
The heartwood is light brown in colour, often with a green tinge, or green streaks, and is clearly defined from the lighter coloured sapwood. The grain is usually straighter than in the

English and Dutch elms, and is considered not quite as coarse in texture. It weighs about 690 kg/rn3 when dried.

Drying
Dries fairly rapidly and fairly well with less tendency to distortion and splitting than common elm. It still requires care in sticking and drying methods however.

Strength
Wych elm is similar to oak in most strength properties, and almost equal to ash in toughness. It is not such a good steam-bending timber as Dutch elm.

Durability
Non-durable.

Working qualities
Easier to work than both English and Dutch elm; there is less tendency to bind on the saw because of the straighter grain. and since distortion is relatively low, planing and moulding is more easily carried out. It can be worked to a good finish and it can be glued, stained and polished satisfactorily, while it takes nails without splitting.

Uses
While its uses are similar as those of English or Dutch elm, it is in greater demand for boat-building because of its straight grain and milder characteristics, for planking, keels, and deadwood.

The burrs that occasionally form on the boles of elm trees may produce highly decorative veneer, but even when carefully selected, the resultant veneer needs to be used carefully since if the finished article is used in situations where atmospheric conditions are subject to wide changes, as for example in ocean going ships, which might meet extremes of atmosphere in a single voyage. then panels and doors faced with elm burr could develop cracks and blisters due to the refractory nature of the wood.