Wood foam cores manufactured from Eucalyptus fiber/epoxy adhesive and 4,4′ oxybis(benzene sulfonyl hydrazide) (OBSH), ethyl acetate (EA), and microsphere polymer bead (Expancel®) as foaming agents were investigated. A 10 phr of OBSH showed superior properties of the 0.50 g/cm3 wood foam and that 0.70 g/cm3 was the optimal density. Also, 17 phr of EA loading gave rise to the better mechanical properties and was considered the optimal content. The microsphere polymer bead did not achieve significant expansion under the conditions employed. Manufacturing of single (X1) and double (X2) layer of lightweight sandwich structures engineered woods with teak/glass fiber-reinforced polymer (GFRP) skins was studied. The enhancement of the sandwich structures’ properties was mainly contributed by the core and also by the added thin interlaminated GFRP layer. In X1 and X2 sandwich structures, with the same volume fraction of core(s), marginal improvement occurred in the properties, caused by the addition of the thin inter-layer of GFRP. Small contributions of the core properties on the sandwich structures were also demonstrated. The sandwich structure derived from the OBSH core was superior in mechanical properties and heat distortion temperature (HDT). The sandwich structure made from EA was unsuccessful in achieving water resistance.