Foundations First

Foundations First: Decoding Stick-Built and Modular Building Differences

What’s the Difference Between Foundations for Stick-Built and Modular Buildings?

Modular projects offer clear benefits, such as efficiency, cost savings, and speed. But what about their foundations? Do they differ from the foundations of traditional stick-built buildings? Architects and developers frequently ask this question. As structural engineers, we will explain the key distinctions.

The main differences relate to construction methods, load transfer to the foundation, and adaptability to site conditions. Let’s explore further.

The Basics of Stick-Built Foundations

Stick-built construction starts on-site, with workers building everything piece by piece. The foundation supports the loads from exterior and interior walls. Depending on the project, the foundation could be a slab-on-grade, a raised crawl space, or a full basement.

Stick-built foundations provide flexibility. Builders can customize them to fit specific designs during construction. Additionally, these structures easily adapt to elevation changes in grading or between lots, making them ideal for townhomes with stepped ground floors and attached garages on sloped lots. However, building on-site takes more time and depends on favorable weather.

Foundation for stick-built Townhome
Foundation for stick-built Townhome, photo from our EVstudio Field Service team

Foundations for Modular Buildings

Modular construction takes a different approach. Workers fabricate building components off-site and assemble them on-site. The foundation must be ready beforehand and support the loads from the modules’ structural frames. Modular foundations may include:

  • Pier and Beam Systems: Concrete piers placed precisely to support the modules.
  • Reinforced Slabs: Slabs with extra reinforcement under key load points.
  • Perimeter Walls: Supporting the module edges with added piers for interior loads.

Modular foundations require preparation because the pre-fabricated modules must fit exactly. While they can handle some elevation differences, they are less adaptable than stick-built foundations when dealing with major grading or lot elevation changes. This limitation is especially evident in townhome applications. However, preparing the foundation while modules are built in the factory significantly shortens project timelines.

Foundation for Modular Multifamily
Foundation for Modular Multifamily, Justice Center Apartments in Breckenridge

Precision and Tolerances: Equally Critical for Both

Precision is crucial for both stick-built and modular foundations. Tolerances depend on the type of hold-downs and connections used. Even minor misalignments can cause significant problems. Whether the project involves stick-built or modular construction, precise foundation layout and leveling are essential for success.

The Bottom Line

Stick-built and modular buildings aim to create durable, safe, and functional structures. Both foundation types must follow general building codes and accommodate either continuous or concentrated loads. The main difference lies in adaptability. Stick-built construction handles elevation changes in grading or lot differences more easily. Modular foundations excel in efficiency and precision but adapt less effectively to challenging site conditions.

If you’re planning a project, consult a structural engineer from EVstudio early in the process. A solid foundation is the cornerstone of any successful build, regardless of the construction method.

[RECOURSE]

2021 International Residential Code (IRC)

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Modular Overview – EVstudio

Volumetric Modular vs Panelized Construction – EVstudio

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