Specifying C16, the most common strength grade from UK sawmills, could cut both material costs and embodied carbon in construction. C16 has a 16N/mm2 bending strength and spans about 10% less than imported C24, but performs similarly in vertical applications like stud walls. At the sawmill it costs roughly £30 to £40 less per cubic metre, and because it is typically harvested after 35 to 45 years, it can store carbon in buildings faster than C24. The article uses Roderick James Architects' COP26 House as a proof point: almost every structural element used C16, and the building hit 490 kgCO2e/m2, 22% below RIBA's 2030 Climate Challenge target. The main barriers are not technical. Architects, engineers and contractors need to coordinate earlier, clients need to ask for UK timber, and regulators need to stop treating all timber as a fire risk. If those pieces move, C16 becomes a straightforward low-carbon default.
