During heat treatment process water is removed from the wood causing transformation of its chemical composition [4; 5; 6]. Such modification takes place in the form of hydrolysis, decarboxylation and oxidation reducing hygroscopicity of the wood [4]. Heat treated wood is generally dimensionally more stable having reduced shrinkage and swelling characteristics due to fluctuation in moisture content within the surrounding environment. Hemicelluloses is the most reactive element in the cellwall having a low molecular weight among the other three main components of any lignocellulosic materials and degrades at lower temperature levels than cellulose and lignin during the heat treatment [4; 6; 7]. It is also a well-known fact that breakage of the lignin polysaccharide compounds by organic acids from hemicelluloses in the cellwall is inevitable during the heat treatment [4; 8]. One of the most important disadvantages of heat treatment is its adverse influence on mechanical properties of wood. Various studies clearly revealed that heat exposure adversely influences most of the mechanical properties of wood [9; 10; 11; 12]. Probably the first investigation related to effect of heat on mechanical properties of wood was carried out by [PERSON] et al., in 1944 and determined that modulus of rupture of different wood species decreased 20% as a result of heat exposure between 160 \({}^{\circ}\)C and 280 \({}^{\circ}\)C [13]. Another study found that there is decreasing linear relationship between bending characteristics including modulus of elasticity, modulus of rupture and heat treatment processing parameters [14]. Based on the findings of previous studies it was determined that the main reason of adverse effect of heat treatment on mechanical properties of wood could be related to the degradation of hemicelluloses in the cellwall [4; 15]. The crystallization of cellulose, specifically on the amorphous zone would be also one of the main elements playing a major role on this issue [15; 16; 17]. Heat treatment also modifies molecular structure of wood as a result of decomposition of the polymers causing reduction of elasticity. Therefore any wood products exposed to heat treatment will have lower mechanical properties including modulus of elasticity and modulus of rupture. Negative effect of heat treatment on mechanical properties of wood has been studies in past investigations and the decrease of hemicelluloses was determined as the major reason for such reduction [4; 16; 18; 19]. When flexible bonding between cellulose and hemicelluloses is replaced and left only rigid cellulose bonds, flexibility of the products is simply decreases [4; 20]. Regarding adverse effect of heat treatment on mechanical properties of wood, eastern redcedar samples were exposed to temperature levels of 120 \({}^{\circ}\)C, 160 \({}^{\circ}\)C and 190 \({}^{\circ}\)C for 6-h and it was found that their shear strength reduced from 44.4% to 64.1% [10]. It appears that it can clearly be concluded that heat treated wood products are not ideal for structural applications where high strength requirements from the unit are priority [20; 21]. In addition to bending properties of heat treated wood, its hardness is also adversely influenced due to degradation of hemicelluloses. Heat treated eastern redcedar, yellow poplar and southern pine samples had an average of 50% reduction in their Janka hardness [10]. Changes in structure of lignin also reduce overall of hardness of heat treated wood [4; 17]. In general heat treatment process of wood consists of several major levels, namely drying, application of heat treatment schedule, cooling and finally conditioning [9; 10]. A previous study found that the swelling values of poplar, pine, and spruce samples decreased ranging from 50% to 80% as a result of exposure them to heat treatment process having a temperature ranging from 180 to 200 \({}^{\circ}\)C [11].