English-grown hardwoods passed tests for construction timber products in research focused on England’s reliance on imported lumber and the low-value use of its hardwood harvest. The findings come from Building from England’s Woodlands, a Forestry Commission-funded case study written by researchers from NMITE, Edinburgh Napier University, BE-ST, Ecosystems Technologies and dRMM Architects.
The work examined whether hardwood species grown in England could be used in construction instead of remaining a low-value resource. The UK imports 68% of the sawn timber it uses, while hardwood species such as birch, oak, ash and beech account for 77% of woodland area in England. The current use of hardwood harvest for energy stands at 85%.
Researchers tested oak, ash, beech, sycamore, birch, sweet chestnut, alder and poplar sourced from sawmills around the country. More than 2,000 tests measured bending strength, stiffness, density, compression strength, hardness and moisture behaviour. Most tests used small clear specimens, while full-size testing remains needed for strength grading assignments under structural standards.
The tested hardwood species were compared with softwood species already available for construction. Poplar properties aligned with UK Sitka spruce, while sweet chestnut and alder were similar to UK larch. Among the prevalent hardwood species shown, birch had the highest average bending strength, sweet chestnut had the lowest, and all were stronger than spruce on average.
The project combined UK-grown softwood with English hardwoods, including ash, beech, birch and sycamore, in engineered timber products. Hardwood was placed in the outer lamellas of glulam beams and in the outer layers of CLT panels, where higher strength and stiffness are needed. Hybrid glulam beams exceeded strength and stiffness requirements, while delamination and bond-strength tests met or exceeded relevant product standards.
The CLT tests showed that using hardwood in the outer layers can reduce panel thickness by around 10-15% while maintaining required stiffness. Similar hardwood-softwood combinations in glulam allowed slimmer beams. The results included spruce-ash and spruce-birch combinations.
The research moved from laboratory samples to construction prototypes. These included a hybrid portal frame with a knuckle joint, a cross-laminated barrel vault system and a hybrid glulam beam installed in a building extension at the New Model Institute for Technology and Engineering.
The demonstrator was assembled and displayed in November 2025 at V&A South Kensington in the exhibit “dRMM: Building from Forests.” Its components included oak knuckles, hybrid oak and Douglas fir glulam beams, a cross-laminated barrel vault, a mixed hardwood hybrid CLT wall, a mixed hardwood hybrid CLT floor, Douglas fir columns and softwood joists.
At NMITE’s Skills Hub in Hereford, a planned imported timber beam was replaced with a UK-grown hybrid glulam beam combining spruce and ash. The spruce and ash were harvested, processed and installed within the UK. Full-scale bending and glue-line shear tests were required before the beam could be used in the building.