The future consumption and substitution of wood products in the building industry is not well analyzed and examined hence demand for wood in the industry remain uncertain. The study on forecasting consumption and substitution of sawnwood in building industry was carried out in Dar es Salaam city. Consumption forecasts of sawnwood for years 2016, 2021 and 2026 were determined through income elasticity of demand forecasting model. The sampling unit was obtained from a list of wards, building contractors and architects in Dar es Salaam city. Random sampling with replacement was employed with an intensity of 20% - 100% depending on the population, availability of respondents and willingness to respond. Questionnaires were used to obtain data from interviewees. Statistical data of sawnwood and substitute building materials were recorded in data sheets. Data collected were analyzed using SPSS and MS Excel programmes. The consumption of sawnwood and substitute building materials were assessed in doors and windows. Buildings were categorized into Lower, Medium, and High categories. The lower category involved all none storey buildings and consumed an average of 2.69 m3 per building unit while medium category (1-3 storey) consumed 3.1 m3 of sawnwood per building unit. The last category involved buildings with 4 storeys and above which according to the results consumed an average of 5.3 m3 of sawnwood per building unit. The study show that in year 2011, Dar es Salaam consumed a total of 8,706.9 m3 of sawnwood for doors and window frames in about 2878 building units that were built in that same year. Kinondoni district consumed 42.2% of the total sawnwood while Ilala district consumed 34.8% of total sawnwood and Temeke district consumed 23% of the total sawnwood consumed in windows and doors in Dar es Salaam city in the year 2011. The per capita building consumption of sawnwood for Dar es Salaam in 2011 was estimated to be 2.7 m3 while for aluminium was 46.2 m2. Sawnwood substitution was highly observed in windows compared to doors with aluminium being the main substitute material. The per capita building consumption of sawnwood in 2026 is estimated to be 3.4 m3 which is an increase of 23.4% compared to 2.7 m3 observed in year 2011. For aluminium, per capita consumption for 2026 will be about 86.8 m2 which is an increase of 88% compared to 46.2 m2 which was observed in year 2011. Sawnwood consumption in none storey buildings will still grow fairly fast because majority of the buildings in urban centers particularly Dar es Salaam are being built by low and middle income people for residential purposes. Therefore, the commercially unknown and underutilized sawnwood species need to be publicized on their strength properties, resistance to weather and durability for future consumption in the building industry.