C16 construction timber is a widely used strength-graded softwood (coniferous wood) commonly employed in building and DIY projects, particularly in the UK and Europe. The "C" stands for coniferous, and the "16" refers to its characteristic bending strength of 16 N/mm² (Newtons per square millimetre), as defined in the European standard BS EN 338.

It is typically made from species such as spruce, pine, or fir. The timber is usually kiln-dried to a moisture content of around 20% or less, which improves stability, reduces the risk of warping, shrinking, or cracking, and makes it easier to work with.