This study investigated potential utilization of the extraction yield of ash and cedrus tree leaves as extender in urea-formaldehyde (UF) and polyvinylacetate (PVAc) adhesives. The extraction solutions of ash and cedrus leaves (10% by weight) were added into the liquid UF and PVAc adhesives. 9-layer laminated veneer lumber (LVL) boards were produced using the UF and PVAc adhesives modified with the extraction solution. For comparison of the extraction solution, water (10 wt%) was added in the adhesives. The LVLs bonded with extraction solution/UF adhesive were hot pressed for 10 min at 105 degrees C while the ones bonded with the extraction solution/PVAc adhesive were hot pressed for 2 h at 20 degrees C. As compared to the addition of water, the bending strength and splitting strength in transverse direction of the LVLs increased by 8.2% and 13.9%, respectively, as the extraction solution of ash leaves were incorporated into the UF adhesive. The extract of ash leaves had better adhesion performance in the UF and PVAc adhesives than that of cedrus leaves. The extract of the leaves was more compatible with the UF adhesive than the PVAc adhesive. Based on the findings of the study, it was concluded that the extracts of ash and cedrus leaves could be efficiently used as extender in the UF adhesive. (C) 2012 Elsevier B.V. All rights reserved.