Washington State University in collaboration with Colorado State University has secured a U.S. Department of Housing and Urban Development grant to develop comprehensive guidelines for designers and builders working on modular units and factory-built housing projects using mass timber and light wood frame members.

Led by Pouria Bahmani, assistant professor in WSU's Department of Civil and Environmental Engineering, the two-year grant aims to make modular housing, in which housing components are built and prefabricated in factories rather than at individual construction sites, more viable and help to address housing affordability in the U.S.

"There's a housing crisis right now," said Bahmani. "We would like to find ways to reduce the cost of housing and construction without compromising safety or the quality of the built environment."

Affordable housing in the United States has been an increasing problem in recent years due to a low housing supply, shortage of construction materials, and increases in construction costs. Estimates indicate that the U.S. has a shortage of more than three million homes, he said, and standard and conventional building construction methods haven't been able to keep up with the demand.

"There is no way to solve the housing shortage except to construct more affordable housing, so that's the only thing we can and we should do," he said. "If we continue using the same construction methods, housing prices will likely rise due to the increasing demand outpacing supply."

Modular construction offers a potential solution because it can be done more quickly and efficiently than standard building and offers higher quality. Unlike traditional on-site construction, which can be delayed by winter weather or a shortage of skilled workers, modular housing projects can be built year-round and in multiple shifts, potentially reducing construction costs.

"Instead of being constructed on-site by workers, modular homes are constructed in factories using assembly line techniques," he said. "Modular units are pre-built, pre-fabricated and cut to size, then shipped to the construction site for final assembly. This can significantly reduce construction time and costs."

Because it's lightweight compared to other building materials, mass timber products would make for efficient and economical transport of modular housing units to job sites. Mass timber members are engineered wood products composed of layers of wood lumber or strands bonded together with adhesive under high pressure. They can be designed as beams, column, shear walls, and other structural members in buildings and weigh less than concrete or steel materials. Mass timber can be prefabricated and assembled more easily than other building materials, reducing on-site labor and time compared to steel or concrete structures, said Bahmani.

As part of the $225,000 grant, the WSU researchers are developing structural and construction guidelines for a hybrid modular construction approach, combining mass timber with light wood frame members to optimize the design of modular units. These guidelines will lead to the development of a preliminary standard that considers factors such as building occupancy, loading conditions, building height, construction materials, and modular unit transportation. This standard will aim to ensure the safe, efficient, and optimized design of hybrid modular construction.

While modular construction can lead to lower housing costs and construction time, these guidelines and pre-standards themselves can also lower costs, said Bahmani. "By streamlining the design process, these guidelines will directly contribute to more affordable housing by reducing design time and construction costs" he said.