The effect of TiO2 and/or clay nanoparticles on water vapour permeability and the reaction to fire performance of coated and impregnated spruce wood were studied. Water vapour permeability properties were used to assess the moisture transfer properties and durability of the specimens using the cup test. The reaction to the early stage fire development properties of the specimens was analysed using a small scale cone calorimeter test. Comparisons between the different treated and untreated specimens on the moisture and reaction to fire performances were performed. The results revealed poor reaction to fire and water vapour resistance of specimens treated with TiO2 and/or clay nanoparticles containing treatments. Copyright © 2013 John Wiley & Sons, Ltd.