Types of oak

European Oak

Quercus robur (Q. pedunculata) and Quercus petraea (Q. sessiliflora) Hybrids between these two species are common.)

Reaches a height of 18 to 30m (60–100ft), varying according soil and locality. Diameter of bole about 1.2 to 1.8m (4–6ft), occasionally more. Forms a straight, clear bole, sometimes up to 15m (50ft) in length, when grown under forest conditions, but carries lower branches when grown in the open. Occurs in pure stands, and in mixed woods where it is often the dominant species.

There is no inherent difference between timber of the two species.

Colour
Yellowish brown. A yellow stain (golden oak) caused by a harmless surface mould is sometimes noticeable during drying, but is not permanent.

Sapwood
Light in colour, usually 25 to 50mm (1–2in) wide, distinct from heartwood.

Grain
Generally straight, but varying with growth conditions. The characteristic ornamental silver grain, due to the broad rays, is seen in quarter-sawn material.

Weight
Variable according to origin and character of growth. Timber of slow growth from Central Europe, such as Slavonian oak, averages about 670kg/m3 (42lb/ft3) and home-grown timber, which is usually of more vigorous growth, about 720kg/m3 (45lb/ft3) at 12% moisture content.

Corrosive properties
A somewhat acidic timber which tends to promote corrosion of metals, especially iron and steel, in contact with it under damp conditions.

Chemical staining
Blue-black stains, formed by reaction of iron with the tannin in oak, are liable to appear on the timber when it is in contact with iron or iron compounds in presence of moisture.

Strength
Slightly lower than European beech.

Drying
Dries very slowly with marked tendency to split and check, particularly in the early stages of drying. In air drying thin piling sticks should be used and some end protection is advisable. In kiln drying there is a considerable risk of honeycombing developing later in the process if drying is forced, and distortion may be appreciable. A yellow stain sometimes develops during the drying process but gradually fades in service.

Staining and polishing
Good

Durability of heartwood
Durable

Preservative treatment
Extremely resistant. The sapwood is permeable.

North American

White American Oak

Quercus spp., principally Q. alba, Q. prinus, Q. lyrata and Q. michauxii.

Under favourable conditions it reaches a height of 30m (100ft), but under less favourable conditions may be of poor form and only 15m (50ft) high. Well-grown trees have a straight, clear bole, length 12–15m (40–50ft), diameter 0.9–1.2m (3–4ft). Eastern half of United States and south-eastern Canada, the distribution varying according to species.

The timber is similar in many respects to European oak.

Colour
Rather variable from pale yellow-brown to mid-brown.

Sapwood
Almost white in colour, distinct from heartwood.

Grain
Generally straight. Quarter-sawn material has a characteristic ornamental silver grain due to the broad rays. Structure and quality vary widely according to the conditions of growth. Oak from the northern Appalachian area is usually slow grown producing a comparatively lightweight, mild type of wood. Oak from the southern States is typically fast grown with correspondingly wide growth rings, producing a harder and tougher timber.

Weight
Slightly heavier than European oak. Average weight about 750kg/m3 (47lb/ft3) at 12% moisture content.

Corrosive properties
A somewhat acidic timber which tends to promote corrosion of metals especially iron and steel in contact with it under damp conditions. Metals, e.g. lead, may also be attacked if exposed to vapours from undried oak. Metals used in association with oak should be protected by painting or galvanising.

Chemical staining
If the timber comes into contact with iron or iron compounds in presence of moisture, blue-black stains are liable to appear due to reaction between the iron and tannin present in the wood.

Strength
Slightly lower than European beech.

Drying
Dries relatively slowly with a tendency to check, split and honeycomb.

Staining and polishing
Good

Durability of heartwood
Durable

Preservative treatment
Extremely resistant. Sapwood moderately resistant.

Uses
Milder to work than European oaks and suitable for furniture, cabinet making and joinery. A good timber for constructional work owing to its strength and durability. A good flooring timber, suitable for parquet and strip flooring. Suitable for tight cooperage and used particularly for manufacture of whisky casks.

Red American Oak

Quercus spp. Commercial American red oak is made up of a number of species, principally Quercus rubra (northern red oak) and Q. falcata var. falcata (southern red oak).

Resembles other oaks in appearance but heartwood usually has a reddish tinge. Generally coarser in texture and has a less attractive silver grain figure than American white oak, due to its smaller rays. Exhibits considerable variation in structure and quality, depending on species and conditions of growth. Southern red oak is typically of more rapid growth than northern red oak and produces a rather harder, heavier and coarser textured wood. Average weight about 770kg/ m3 (48lb/ft3), seasoned, similar to American white oak. Strength rather variable, but similar on average to American white oak and slightly lower than European beech. Medium movement.

Processing
Drying properties similar to other oaks. Kiln Schedule C. Working properties vary according to the density of the wood. Gluing variable. Has very good bending properties.

Durability and preservation
Heartwood non-durable. Moderately resistant to preservative treatment.

Uses
Considered inferior to white oak for high-class furniture and decorative work. Used for flooring, vehicle construction, interior joinery, furniture and veneer, but unsuitable for exterior work because of its lack of durability. Not suitable for tight cooperage because of its porosity. Has been planted on a small scale in Great Britain. Tests on the timber have shown that it is generally similar to timber from America.

Red American Oak

Quercus spp. Commercial American red oak is made up of a number of species, principally Quercus rubra (northern red oak) and Q. falcata var. falcata (southern red oak).

Resembles other oaks in appearance but heartwood usually has a reddish tinge. Generally coarser in texture and has a less attractive silver grain figure than American white oak, due to its smaller rays. Exhibits considerable variation in structure and quality, depending on species and conditions of growth. Southern red oak is typically of more rapid growth than northern red oak and produces a rather harder, heavier and coarser textured wood. Average weight about 770kg/ m3 (48lb/ft3), seasoned, similar to American white oak. Strength rather variable, but similar on average to American white oak and slightly lower than European beech. Medium movement.

Processing
Drying properties similar to other oaks. Kiln Schedule C. Working properties vary according to the density of the wood. Gluing variable. Has very good bending properties.

Durability and preservation
Heartwood non-durable. Moderately resistant to preservative treatment.

Uses
Considered inferior to white oak for high-class furniture and decorative work. Used for flooring, vehicle construction, interior joinery, furniture and veneer, but unsuitable for exterior work because of its lack of durability. Not suitable for tight cooperage because of its porosity. Has been planted on a small scale in Great Britain. Tests on the timber have shown that it is generally similar to timber from America.