A factory-built home is only as good as the pad it sits on. The building code treats its foundation like any other: footings on undisturbed soil, organics removed, depth set by soil type and frost, and a dry, vented crawl space. The main difference is that a home that passes the CSA Z240.2.1 deformation resistance test may instead sit on a surface foundation built to CSA Z240.10.1, which changes how deep you have to dig.
This is a technical checklist for the housing manager or technical services officer getting lots ready while the homes are built in the factory. It covers the foundation choices the code allows, what the soil has to tell you, how to build a crawl space that stays dry, winter excavation, services at the set, and the inspections a lender or funder will expect. Where to put a home (flood, wildfire and permafrost risk) is covered in our siting guide; the trade-offs of keeping a home on its transport skid are covered in our modular housing overview. This post starts once the lot is chosen.
Code references below quote the British Columbia Building Code 2018, Part 9, because it is freely readable online and shows how Part 9 handles these questions. The code edition in force where you build, and the rules that apply on reserve land, may differ. Treat this as general information and confirm with your building inspector, ISC and your lands office.
What does the building code require of a factory-built home's foundation?
Manitoba's bulletin on manufactured homes (ITS 25-007) reproduces the National Building Code's explanatory note: "The NBC applies the same requirements to site-built and factory-constructed buildings." CSA A277 certification lets an inspector rely on the factory's label for the closed-in walls, floors and roof. But it covers only the plant: "CSA certification processes (A277 or Z240 MH Series) only apply to work completed in the certified manufacturing facility." Everything done on site, starting with the foundation, is inspected like a site-built house. Our CSA A277 guide explains the label in more detail.
The same note explains the one big exception: "The NBC does reference CSA Z240.10.1, 'Site preparation, foundation, and installation of buildings,'" and that standard "contains requirements for surface foundations where buildings—not just houses—comply with the deformation resistance test provided in CSA Z240.2.1." In other words, a home stiff enough to tolerate some ground movement can sit on a foundation designed for that, rather than footings below frost.
On reserve, provincial codes may not apply directly. Manitoba's bulletin says "First nations land under federal jurisdiction are not subject to the Act or the MBC." Your Nation's own building bylaw, funding agreement or lender will usually set the code and the inspector. Our on-reserve approvals guide covers who does what.
Full foundation, piers or surface foundation: which path fits?
In the BC Building Code 2018, Section 9.15, Article 9.15.1.3 sets out two routes for a home whose superstructure passes the Z240.2.1 test: the foundation "shall be constructed in conformance with" either "the remainder of this Section" or CSA Z240.10.1. The practical choices are:
- Conventional Part 9 foundation: concrete or wood footings and foundation walls enclosing a crawl space or basement. Part 9 covers these only "on stable soils with an allowable bearing pressure of 75 kPa or greater." Other cases "shall be designed in accordance with Section 9.4," which in practice means an engineer.
- Piers: "Where pier-type foundations are used, the piers shall be designed to support the applied loads from the superstructure." For a one-storey building, piers go under the principal framing members and are "spaced not more than 3.5 m apart along the framing," unless designed for more, and pier height "shall not exceed 3 times their least dimension at the base of the pier."
- Surface foundation to CSA Z240.10.1: for homes that pass the deformation resistance test. Get the current edition of the standard from CSA Group and have your builder confirm in writing that the units qualify.
- Permafrost: "Buildings erected on permafrost shall have foundations designed by a designer competent in this field in accordance with the appropriate requirements of Part 4." No prescriptive route exists.
Screw piles, steel piles and engineered grade beams fall outside the prescriptive Part 9 tables, so expect them to need an engineer's design and sign-off. Ask your builder for the point loads and beam locations of each unit before the foundation is designed, because the supports must line up with the home's main beams.
How deep does the foundation need to go?
The BC Building Code 2018, Section 9.12, sets minimum depths by soil type, drainage and whether the space below is heated. In Table 9.12.2.2, rock and coarse-grained soils have "No limit" in most cases. For clay or soils not clearly defined, depths are "1.2 m but not less than the depth of frost penetration" where the foundation contains no heated space and drainage is poor. A foundation insulated to keep heat from the soil beneath the footings must meet the stricter no-heated-space depths.
The key rule for factory-built homes is in Sentence 9.12.2.2.(6): the depths "do not apply to foundations for" buildings that are not masonry or masonry veneer and "whose superstructure conforms to the requirements of the deformation resistance test in CSA Z240.2.1." Depths can also be reduced "where experience with local soil conditions shows that lesser depths are satisfactory, or where the foundation is designed for lesser depths." A shallow surface foundation is not a shortcut, though. It must be designed to tolerate frost movement, so plan access under the floor in case the home needs re-levelling.
What does the soil need to tell you before the pad is built?
CMHC's Section 95 Project Delivery Guide asks applicants "Is a geotechnical report available for the project site(s)?" and "Have you completed an Environmental Site Assessment?" Even where neither is required, a geotechnical investigation is the cheapest insurance against a home that heaves or settles. The code sets the basic rules for what the footings bear on:
- "The topsoil and vegetable matter in all unexcavated areas under a building shall be removed," and "The bottom of every excavation shall be free of all organic material."
- "Excavations for foundations shall extend to undisturbed soil."
- "Footings shall rest on undisturbed soil, rock or compacted granular fill." Granular fill must not contain pyritic material in damaging concentrations.
- Where a foundation rests on gravel, sand or silt with a high water table, "the footing width for walls shall be not less than twice the width required" (Sentence 9.15.3.4.(3)).
Ask the geotechnical engineer for allowable bearing pressure, frost-susceptibility of the soil, groundwater level and recommended fill. Those numbers decide whether Part 9 applies and how the pad is built.
How do you build a crawl space that stays dry?
Many factory-built homes sit over a crawl space. The BC Building Code 2018, Section 9.18, sets the basics. Decide first whether the crawl space is heated, because the rules differ. A crawl space counts as heated if it is used as a hot-air plenum, has unsealed and uninsulated heating ducts, or is not separated from the heated house.
- Access: "An access opening of not less than 500 mm by 700 mm shall be provided to each crawl space where the crawl space serves a single dwelling unit."
- Ventilation (unheated): "not less than 0.1 m2 of unobstructed vent area for every 50 m2 of floor area," with vents on opposite sides and screened against snow, rain and insects. Heated crawl spaces are ventilated under Section 9.32 instead.
- Ground cover (unheated): at least 50 mm of asphalt, 100 mm of 15 MPa concrete, Type S roll roofing, or 0.10 mm polyethylene, with sheet joints "lapped not less than 100 mm and weighted down."
- Ground cover (heated): 0.15 mm polyethylene as part of the air barrier, joints lapped 300 mm and sealed, perimeter sealed to the foundation wall.
- Drainage: "the ingress of water into a crawl space shall be controlled by grading or drainage."
- Service access: where cleanouts, traps or burners are in the crawl space, provide an access way at least 600 mm high and wide to the equipment.
Skirting closes the gap between grade and the home on a pier or surface foundation. Treat it as part of the crawl space: vented if the space is unheated, insulated and sealed if it is heated, and removable where you need access.
Winter work. Section 9.12 requires that "Excavations shall be kept free of standing water" and that "The bottom of excavations shall be kept from freezing throughout the entire construction period." If homes arrive on a winter road, plan to finish pads and piles in the summer or fall before. Build the excavation and foundation work into the schedule so it is done and inspected before the units ship.
What needs to be ready on set day?
CMHC's guide asks "Is the site fully serviced? (access, electrical, water, sewage)" Use that as the minimum before the trucks leave the plant:
- Foundation or pad complete, inspected, level and marked with the unit's footprint and beam lines.
- Access for trucks and a crane or set equipment, with a firm, cleared staging area.
- Water and sewer stubbed to the right location under each unit, protected from frost. Our lot servicing guide covers the planning.
- Electrical service ready to connect. Manitoba's bulletin, for example, notes that Manitoba Hydro enforces electrical code requirements outside Winnipeg; ask the electrical authority for your area about permits.
- Fuel, propane or other heating connections arranged.
- Grading planned to slope water away from the home once it is set.
Which inspections happen at and after the set?
If CMHC is financing the homes, its Section 95 guide sets the checkpoints. For all projects, "CMHC does require a pre-backfill, pre-drywall, and final code compliance confirmation." For ready-to-move units, the final advance needs "Code Compliance Certificates (Pre-Backfill, CSA sticker, and Final)," plus "Confirmation of 'in-transit' Insurance from the facility to the site" earlier on. Book the pre-backfill inspection before the foundation is covered: once backfilled, it cannot be seen.
Inspect each unit for transport damage as it arrives. Manitoba's bulletin warns that if a home is damaged in transit or on site, "The building inspector may require covered building elements to be uncovered to inspect for deficiencies." Photograph each section on arrival and keep the delivery records with the inspection reports.
Where does a builder fit in?
Your builder should give you unit dimensions, weights, beam and support locations, and service connection points early enough to design the pad. Herauf Modular, a division of Herauf Enterprises, builds homes and community buildings as finished sections indoors in its Saskatchewan and BC plants, then delivers and sets them on site. Most builds are manufactured and delivered in about 16 weeks, with foundations, pads and services prepared on site at the same time, and every unit meets or exceeds CSA A277 and the National Building Code for climate zones 6 through 8. At Buffalo Lake Métis Settlement, 20 homes delivered with CMHC and government agencies were installed within days. For Nisichawayasihk Cree Nation, housing was built on the Herauf rapid portable skid system, so the build did not wait on a poured foundation. To plan site preparation for your project, contact Herauf; we reply within one business day.
This guide is general information, not legal or financial advice. Program rules change: confirm the details with the program, your Indigenous Services Canada regional office or CMHC before relying on them. Herauf does not administer any program or apply on a community's behalf.