Maximizing efficiency: The unique process of designing for modular construction

Designing housing for modular construction is a unique process in the building industry — it requires careful consideration from the early stages of the project to ensure efficient and cost-effective results, says Peter Todorowich, Big Block’s VP of Production & Construction.

“You have to take in every consideration right at the start of the project,” Peter said. “So even how it's going to look at the end plays a factor right at the beginning.”

There are some specific methods modular-built housing uses that differ from traditional stick building, including building for increased rigidity during transport and craning. We also try to complete as much as possible in the factory, especially in areas where on-site labour is both a premium and scarce. These types of considerations change the way we need to approach our projects.

Connecting self-contained suites

When designing modules, it’s ideal to have suites self-contained in one mod or multiple suites fully contained in one mod. Connections can be made side to side or up and down to have suites made up of multiple mods, but this adds work, time and expense, so we try to reduce these connections when possible. The fewer connections to make on site, the more effective modular construction becomes.

When you do have a plan that includes more connections, it takes creativity and a deep understanding of how modules fit together, says Peter.

"You have to be aware of where those connections are in relation to equipment or adjacent rooms, and how it interacts with the rest of the structure." 

In the example below of an apartment building completed in Saskatoon, the mod has eight bathrooms spanning over four partial suites, which formed unique and spacious floor plans.

Since the modules were being transported in the prairie provinces, we had the ability to design and transport a wider load, giving us more space for arranging multiple suites into one mod.

As you might imagine looking at the blueprint above, craning mods into place to be perfectly in line with another is crucial. Our goal with any project is to maximize the size and repeatability of modules while reducing the amount of suite connections. 

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Electrical, plumbing, and HVAC also need to be taken into account — workers need easy access to make these connections on site, as well as an easy and aesthetic way to close these access points once connections are made. In townhouse models, we try to make these connections in utility rooms or closets, and these connections can be made in floors, ceilings, or walls. For townhouse style builds, power, gas, water, sanitary mains and telecommunication service lines can be run through a crawlspace foundation, eliminating the need to trench and backfill.

With modular construction, Peter says pre-planning is critical.

“You have to be on point with connections, making sure everything is lined up precisely during the build so when connections come in, it can be connected easily with minimal movement.”

The symmetry of mods is also taken into account — a more symmetrical mod will have weight that is more evenly balanced, making craning more balanced. Unbalanced mods will demand a more skilled craning team to ensure a safe and stable lift, which may involve using longer straps on one end or offsetting pick points.

Exterior style

With any type of construction, building square and straight is more economical than introducing cut-ins and curves. While some appreciate a boxy, minimalist aesthetic, to others it can feel plain. Angled or curved walls are by no means impossible but they do add additional costs and time, so are best done sparingly to preserve resources.

Again, pre-planning is the key to designing modular building exteriors, says Peter.

“You have to make sure you have the proper supports in your main structure in place for the final design you want,” he said. “Even though it starts as a box, it can turn into anything at the end of the day. All it takes is a little forethought.”

Below is a before and after example of a townhouse project where we cantilevered the top mod on the back, added a canopy roof on the front, and had trim board on the vertical joints. Building an architectural feature on connection points is typical for modular builds.

Flat roofs with a low slope and/or internal drains can be completed in the factory, as allowed by height restrictions. Typically, we ship the upper mods with a flat roof and add trusses on top once on site, giving us the ability to design and build any roof desired. 

There are options where we can build gable roofs in the factory and hinge them during transport. This does affect transport constraints, but depending on the type of roof it is worth exploring. 

Module dimensions & structure

Designing the dimensions of a modular building involves balancing module length and width with shipping costs. Weight is typically not a concern. The modules are designed to be transported from the factory assembly line to their final destination, and the dimensions of these mods vary based on the shipping region and factory location — for example, British Columbia has stricter constraints on dimensions compared to Alberta, Saskatchewan, and Manitoba.

“There are differences between B.C. and the Prairie provinces,” said Peter. “In B.C., it is a lot more challenging to get a mod through, and you have to take those design constraints into consideration. The mods might be smaller but then you get more creative with utilizing the space to make it workable and liveable.”

The length is measured from the front of the transport truck to the back of the load. For width, it's important to leave a minimum of two inches less than the outside sheathing measurement to account for tolerances and other factors like building paper, EPDM lapping, and window or door brick molds.

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The maximum module height varies depending on the project and factory considerations. Adding pre-engineered wood joist floor and ceiling structures to an eight-foot high wall yields a 10-foot three-inch module height, accommodating wiring, pipes, and mechanical elements. Opting for a nine-foot wall increases the total height to 11 feet three inches for those desiring higher ceilings.

Overall, the modular construction process requires careful attention to detail, collaboration, and innovative solutions to unlock its potential. By embracing modular design principles, construction methods can be optimized, offering efficient and cost-effective solutions for a variety of projects.

The Big Block team has extensive experience building with modular technology, and in addition to providing full-service design, we often work with groups who have an in-house design or a pre-existing relationship with an architect, but who lack expertise in modular. As a development partner, we integrate seamlessly and collaborate with your design team, overseeing the concept and design for modular builds.