Mass Timber Social Housing

Defining barriers and developing strategies to enable mass timber construction for housing associations

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There is a growing need for social housing in the Netherlands, especially in urban areas. The construction industry faces the difficult task of quickly responding to this demand while also reducing the embodied carbon emissions of new buildings. A proposed solution to these tasks is constructing mass timber buildings, leading to cheaper buildings and faster construction times while also reducing embodied carbon emissions compared to traditional buildings (Amiri et al., 2020). Due to its high strength and low weight, research finds that mass timber is suitable for reinforced concrete replacement. In doing so, a reduction of 2,4 Million Tons of C02 Equivalent annually can be established.

However, mass timber construction faces barriers—especially when addressing social housing associations due to their strong focus on affordability and risk reduction. Since the construction of social ‘carbon neutral’ housing is a major societal and environmental challenge, this research aims to define the barriers and develop strategies for overcoming these barriers to enable mass timber construction. For this purpose, the central research question is as follows: “What are the barriers for the construction of modular mass timber social housing, and what might be strategies for overcoming them?

Since this question is explorative, a qualitative research approach is used with the double design method. In the first diamond, the barriers are discovered and defined. In the second diamond, the strategies for overcoming these barriers are developed. Expectations are that the demand for mass timber buildings is above average in urban areas where a scarcity of land occurs, and municipalities have non-statutory supplementary ambitions regarding sustainability. Therefore, this research focuses on housing associations operating in urban areas. The barriers are identified by analyzing data obtained through a series of consultations with experts and eight semi-structured interviews with social housing associations. Ten barriers resulted from these interviews, which were classified into four categories.

The first category consists of social, cultural, and organizational barriers in adopting mass timber construction. Housing associations experience unclarity about circular decisions, show risk-averse behavior, and are having difficulties changing. The second category contains sectorial barriers. These include a sectoral knowledge deficiency, strategic alliances with the traditional industry, and the unique project-based approach that forms a barrier for modular construction since it limits the degree of repeatability and standardization. The third category are technical barriers. They consist of the perception among housing associations that modular construction results in uniformity, which is further obstructed by different programs of requirements.

The strategies for overcoming these barriers are based upon insights from an online expert panel meeting. The panel consisted of two representatives of mass timber construction companies, an architect, and an expert on bio-based construction materials. There was consensus among the experts about four strategies, of which the most important is to change the conditions for mass timber. This can be done with long- and short-term knowledge increase. Other strategies include the role of the municipalities and universities. However, to enable mass timber construction structurally, the construction costs must be lowered. The industrialization of modular construction could do so. Another way is letting social housing associations review their decision-making process from cost-based to value- based. This can be done by looking at total expenditure rather than building costs. The third strategy lets suppliers create a (open) building system based on standard floorplans with the flexibility for fitting custom facades. An open building system creates the opportunity for an infill industry to arise and allows a shift from a traditional design process towards product thinking. The fourth strategy is to safeguard the future value of components by using materials with common dimensions, which contributes to a total cost of ownership approach. Changing the responsibility of a product’s maintenance incentives suppliers to use durable and remountable materials, allowing circular business models.

This research answers the central question by presenting the ten barriers and four strategies. In doing so, this research provides implications for academia by combining modularity, mass timber, and social housing. It has delivered a well-ordered list of barriers that provides implications for practice. However, the presented strategies for overcoming these barriers do not guarantee the uptake of modular mass timber construction. Since this is a relatively new topic in the Netherlands, it also requires time to be adopted and deployed in the market. A TCO approach looks most promising to enable modular mass timber construction. Future research should find how to best incorporate this within a traditional- orientated construction value chain.