TALKING TIMBER
Are mass timber buildings viable ?
ANDERS VESTERGAARD JENSEN | UNSPLASH
Exterior Valle Wood , Oslo . Mass timber office building .
A recent study by Stephanus van der Westhuizen , structural engineer at Zutari , looked at the economic viability of a multi-storey mass timber building for South Africa through a development cost comparison .
First , the research investigated whether South African plantations can provide sustainable volumes of high-grade ( S7 , S10 ) timber for a multi-storey mass timber building market . This was followed by the design of two 8-storey commercial buildings , consisting of a mass timber frame and of a reinforced concrete frame , respectively .
A focus group workshop , conducted with industry professionals , assisted in the development of the construction schedules . In the subsequent step , a financial model was used to determine the overall development cost and financial feasibility of the ventures .
Finally , a sensitivity analysis was conducted to investigate the effect of certain variables on the overall profitability of the mass timber frame development . The research also served as a case study for the implementation of Building Information Modelling ( BIM ) in a project team . Through this , an assessment was made regarding the benefits and limitations of BIM . The research revealed that mass timber products would need to be imported to satisfy a rapid growth in the multi-storey mass timber building market in South Africa as current timber supplies ( S5 , S7 , S10 ) are oversubscribed . Studies suggest that future log resources could be added to the market through the development of new plantations , however , these plantations will only become available after 24 to 30 years .
The focus group workshop identified that the construction of the reinforced concrete frame building and mass timber frame building will take 42 weeks and 21 weeks , respectively . The total capital investment required for the mass timber frame development was 10 % more than that of the reinforced concrete frame development ( R115 691 000 versus R105 118 000 ). A 5-year internal rate of return ( IRR ) of 20.9 % and 25.7 % was calculated for the mass timber frame and reinforced concrete frame developments , respectively . Notably , the 5-year IRR of both developments is above the 15 % minimum acceptable rate of return ( MARR ), indicating that they are both financially feasible .
A significant finding of the sensitivity analysis was that the mass timber frame building proved to generate a higher 5 year IRR than that of the reinforced concrete frame once the mass timber building achieved a rental premium of 7.8 % or more . The sensitivity analyses further showed that the importation of the mass timber elements remains an expensive option , with a 16.4 % 5 year IRR for the imported mass timber frame ( R17 : EUR1 exchange rate ). The study highlighted a number of aspects , particularly in the manufacturing sector , that can be addressed in order to develop a sustainable multi-storey mass timber building market . This includes improvement in the sourcing of high-grade structural timber ( S7 , S10 ) and investment into equipment to enable the large-scale production of large beams / columns typically required in multi-storey mass timber structures . Shortcomings were observed in the all-round implementation of BIM , particularly regarding the information provided by South African suppliers of mass timber elements . Nonetheless , a number of the BIM benefits were realised , with the main advantages being 3D visualisation and clash detection .
For the full study , visit http :// hdl . handle . net / 10019.1 / 109142
www . timberiq . co . za // APRIL / MAY 2021 27