English-grown hardwoods have successfully passed testing for use in construction timber products, in research examining the UK’s dependence on imported lumber and the low-value use of domestic hardwood resources.
The findings are from the Building from England’s Woodlands project, a Forestry Commission-funded case study delivered by researchers from NMITE, Edinburgh Napier University, BE-ST, Ecosystems Technologies and dRMM Architects.
The project explored whether hardwood species grown in England could be used more widely in construction rather than continuing to be treated as a low-value resource. While the UK imports 68% of the sawn timber it uses, hardwood species including birch, oak, ash and beech make up 77% of England’s woodland area. Currently, 85% of harvested hardwood is used for energy production.
Researchers tested oak, ash, beech, sycamore, birch, sweet chestnut, alder and poplar sourced from sawmills across the UK. More than 2,000 tests assessed properties including bending strength, stiffness, density, compression strength, hardness and moisture behaviour. Most assessments were carried out on small clear specimens, with further full-scale testing required for structural strength grading in line with relevant standards.
The performance of the tested hardwood species was compared with softwood species already used in construction. Poplar showed similar characteristics to UK-grown Sitka spruce, while sweet chestnut and alder performed comparably to UK larch. Among the commonly available hardwoods tested, birch recorded the highest average bending strength, while sweet chestnut recorded the lowest, although all species demonstrated greater average strength than spruce.
The project also investigated the use of English hardwoods alongside UK-grown softwood in engineered timber products. Species including ash, beech, birch and sycamore were incorporated into glulam beams and cross-laminated timber (CLT) panels, with hardwood positioned in outer layers where greater strength and stiffness are required. Hybrid glulam beams exceeded strength and stiffness requirements, while delamination and bond-strength testing met or surpassed relevant product standards.
CLT testing showed that incorporating hardwood into outer layers could reduce panel thickness by around 10% to 15% while maintaining required stiffness levels. Similar hardwood-softwood combinations in glulam enabled slimmer beam designs, with tested combinations including spruce-ash and spruce-birch.
The research progressed from laboratory testing to real-world construction demonstrators, including a hybrid portal frame with a knuckle joint, a cross-laminated barrel vault system and a hybrid glulam beam installed as part of an extension at the New Model Institute for Technology and Engineering.
The demonstrator was assembled and displayed in November 2025 at V&A South Kensington as part of the “dRMM: Building from Forests” exhibition. Components included oak knuckles, hybrid oak and Douglas fir glulam beams, a cross-laminated barrel vault, mixed hardwood hybrid CLT wall and floor elements, Douglas fir columns and softwood joists.
At NMITE’s Skills Hub in Hereford, an imported timber beam originally planned for the building was replaced with a UK-grown hybrid glulam beam combining spruce and ash. Both timber species were harvested, processed and installed in the UK. Full-scale bending and glue-line shear testing was carried out before the beam was approved for use in the building.
