C24 construction timber is a higher-strength graded softwood (coniferous timber) widely used in structural applications in the UK and Europe. Like C16, the "C" stands for coniferous, and the "24" refers to its characteristic bending strength of 24 N/mm² according to the European standard BS EN 338.

It is typically made from species such as spruce, pine, or fir, and is usually kiln-dried to a moisture content of 20% or less for better stability and performance.