C. excelsa attains very large sizes, reaching 45m or more in height and up to 2.7m in diameter. The stem is usually cylindrical and mostly without buttresses. It occurs in the rain, and mixed deciduous forests.
When freshly cut, or when unexposed to light, the heartwood is a distinct yellow colour, but on exposure to light it quickly becomes golden-brown. The sapwood is narrow, being about 50mm to 75mm wide, and clearly defined. The grain is usually interlocked and the texture is rather coarse but even, and the wood weighs on average 660 kg/m³ when dried.
The timber dries well and fairly rapidly, with only a slight tendency to distortion and splitting.
Medium to difficult – Iroko works fairly well with most tools, though with some dulling effect on their cutting edges, especially when calcareous deposits are prevalent. On quarter-sawn stock, there is a tendency for grain to pick up due to interlocked grain, and a reduction of cutting angle to 15° is usually necessary to obtain a smooth surface. An excellent finish can be obtained if the grain is filled. It takes nails and screws well, and can be glued satisfactorily.
Iroko has excellent strength properties, comparing well with teak, though weaker in bending and in compression along the grain.
Occasional deposits of stone may occur
Joinery – Exterior, Joinery – Interior, Cladding & Decking