By using basalt fibre grids as a reinforcing material, lightweight plywood with improved bending properties could be produced by using low density hardwood veneers and phenol-formaldehyde (PF) adhesives. The improvement in flexural strength would allow it to be used in a wider range of load-bearing applications. In this study, acrylate-coated basalt fibre grids with a grammage of 200g m \(^{-2}\) and uncoated basalt fibre grids with a grammage of 116g m \(^{-2}\) were inserted into the outer glue joints of five-layer lime (Tilia cordata) plywood as reinforcement. The plywood was bonded with two formulations of PF adhesive. The evaluation of the mechanical properties showed increases for the modulus of rupture (MOR) and the modulus of elasticity (MOE). The increase in MOR was up to 25% in the parallel direction of the top layers and up to 49% in the perpendicular direction of the top layers for plywood reinforced with the acrylate-coated basalt fibre grid compared to the unreinforced reference in a raw density-adjusted comparison. After treatment to evaluate moisture resistance under cyclic test conditions (MR), the reinforced plywoods exhibited similar bending strength to the unreinforced reference after standardised climate conditioning. At the same time, the addition of coated basalt fibre grid had no effect on surface soundness (SS). Therefore, the use of coated basalt grid as a reinforcing material could be a good way to produce high-strength plywood using low-density hardwood veneers.
