Here's the situation: you've been handed a project—finding temporary office space for a construction site, a modular office for a growing team, or a flexible building solution for a short-term need—and you've never sourced a modular building before. Facilities gave you a one-page spec sheet. Finance is waiting on a budget number. And you're not entirely sure what questions to ask.

I was there in early 2024. I manage procurement for a 250-person company—roughly $1.2M annually across 9 vendors—and I report to both operations and finance. Our facilities manager handed me a single page of requirements for a warehouse project and said, "Go find out what's available."

What follows is the checklist I wish I'd had. Seven steps, in order.

Step 1: Nail down the use case before you look at a single brochure

Modular buildings cover a wide range—from foldable container offices to multi-unit prefabricated structures. Your use case decides which one fits:

  • Duration: 3 months or 3 years? This drives the lease-vs-buy decision more than anything else.
  • Occupancy: 4 people and 40 people are completely different products.
  • Function: General office, restroom, canteen, or equipment room? These affect plumbing, electrical, and insulation requirements.
  • Site conditions: Can a heavy truck access the site? Is the ground paved or graded?

My first mistake was telling a supplier "quote me a temporary office." Three vendors came back with three completely different products—not comparable at all. Once I switched to a one-line spec—"24×60 ft, three offices, 12 occupants, 18-month use, site is rough-graded"—the quotes became comparable overnight.

Facilities teams usually know how to write that spec better than procurement does. Twenty minutes with them beats three days of rework.

Step 2: Separate "supplier matching" from "supplier selection"

These two get conflated a lot. Supplier matching asks "who can do this type of project." Supplier selection asks "who should we sign with."

If you're sourcing internationally—say, through WillScot sourcing for China-origin procurement—the first step is matching, not quoting. What you provide at the matching stage isn't a budget number. It's:

  • Product type (a "(6 bay) euro modular building" and a "3d modular building" sit on different supply chains entirely)
  • Approximate quantity and delivery cadence
  • Destination and customs clearance method
  • Any specific certifications or standards required

One supplier I contacted asked detailed questions during the WillScot supplier matching phase—they even asked whether our site had a forklift. Seemed excessive at the time. Later I understood: they were determining whether the project could ship as a standard unit or needed to be broken down for reassembly. The more precise the questions, the more accurate the quote.

The inverse is also true. If a supplier responds to your matching request with "we can do anything, just send drawings," that's usually a pass-through broker with no real investment in your project.

Step 3: Run "lease vs buy" as two separate calculations

Most admin buyers default to buying—because "buying means it's an asset." But modular buildings are relocatable by design, and leasing often works out more favorably on the books than a fixed structure would.

Here's how I ran the math:

Buy: Upfront cost + foundation + transport + installation + future removal or resale cost. Upside: no lease constraints. Downside: high exit cost.

Lease: Monthly fee + transport + installation + potential site restoration. Upside: smooth cash flow. Downside: long-term leases can exceed purchase cost.

Our use period was 18 months. Leasing came to roughly 60% of the purchase total, and we didn't need to keep the building afterward—so lease was the clearer choice.

One thing most people overlook: ask about the relocation clause in the lease contract. Some contracts allow you to move the building to another company site during the lease term. Some don't. Our second quote didn't mention this at all—a phone call later revealed that relocation would trigger a second transport and installation charge. That changed the entire cost comparison.

To be fair, this was our calculation at our scale and use duration. If your project runs five years or longer, or requires heavy customization, the lease math probably won't hold. I'd suggest running it past finance before committing either way.

Step 4: Confirm delivery timeline before signing—and write it into the contract

Modular building lead times depend on several variables: factory scheduling, transport distance, site installation conditions, and customization level. If you ask "how long until delivery" and get a vague number, follow up with three questions:

1. When does that clock start—signing date, deposit date, or drawing approval date?
2. How many days for transport? How many for installation?
3. If site conditions don't meet requirements, who absorbs the delay?

One quote I received said "35-45 business days." We wrote the contract term as "installation complete within 40 business days of drawing approval and site acceptance." The site grading ran a week late, and the supplier extended the delivery date citing "site acceptance not passed." Without that clause, we would have absorbed the schedule risk for their factory timing.

On the "temporary house vs modular building" question: if you need rapidly deployable temporary housing with utilities ready to use, a temporary house will typically deliver faster than a custom modular building. But if you need a space that meets local building codes, is usable long-term, and can be expanded, the modular building's customization timeline is unavoidable. Decide which category you're in before asking about lead times.

Step 5: Check compliance and permitting early, not last

Modular buildings are prefabricated, but once they're installed, they still have to comply with local building codes, fire regulations, and land-use rules. I've seen a project where the contract was signed and the installation date was set—only to discover that the site's fire access lane didn't meet requirements. The entire layout had to be redesigned, adding three weeks.

At minimum, confirm three things upfront:

  • What's the local permitting process for temporary/modular buildings? (Some jurisdictions have a simplified path; some don't.)
  • Are there special fire and egress requirements? (Exit count, corridor width, etc.)
  • Does the foundation or anchoring method require separate approval? Custom 3d modular building units usually come with additional approval documentation.

These are best confirmed by someone familiar with local regulations—either an internal colleague or an external consultant. Your supplier can provide technical documentation, but the compliance burden ultimately sits with your company. This is exactly why I mentioned in the matching step that destination information needs to be clear from the start—suppliers who consider compliance during matching save you considerable grief later.

Step 6: Put invoicing and payment terms into your evaluation framework

I learned this one the hard way, which is why it's its own step.

A few years back, I went with a new vendor for a different procurement category. Their price was about 15% below our incumbent. Ordering and delivery went smoothly—right up until the reimbursement stage. They could only issue handwritten receipts. No proper invoice. Finance rejected the expense report outright, and the variance came out of my department budget. Since then, I verify invoicing capability and payment terms before confirming any order.

Modular buildings involve larger amounts and multiple payment stages, so this matters even more. What to confirm:

  • Can they issue the required invoice type (VAT special/general, proforma, etc.)?
  • How are payment milestones structured? (Signing, pre-shipment, post-acceptance)
  • If acceptance fails, what's the retention percentage on final payment?

These should be clarified at the quote stage, not left for contract drafting. If a supplier is evasive about invoicing and payment terms during quoting, I treat that as a risk signal.

Step 7: Plan installation coordination—this is where things most often go wrong

Modular building installation typically requires coordination between the supplier's team and the site construction team. I underestimated this on my first project: on lift day, the supplier's installation crew arrived at 7 a.m., but our site wasn't fully cleared. Two trucks were blocked at the entrance.

I had roughly 30 minutes to decide—keep the crane waiting, or accept the supplier's proposed "unload first, clear later" sequence. Normally I'd hold the original plan, but with the supply chain manager standing there, I let them proceed. We ended up paying two extra hours of crane standby. In hindsight, I should have stuck to the original schedule. But when you're under site pressure with limited time, it's not always easy to get right.

Looking back, three things should have been done in advance:

First, give the supplier a detailed site conditions brief (ground bearing capacity, access width, temporary power/water location).

Second, confirm who's on-site the day of installation—the supplier's project manager or your own facilities staff.

Third, build in buffer time. Modular building installation itself is usually fast—a standard unit can go up in a day—but that depends on site and transport going according to plan. One broken link can turn it into two or three days.

A few common mistakes (and what I'd suggest instead)

Don't make unit price the only criterion. The real cost of a modular building includes transport, installation, permitting, and future removal. I've seen the lowest quote turn out to be the most expensive option once those hidden costs were added back in.

Don't feel sheepish about a small order. Early in my procurement career, I needed a small batch of modular office partitions—not a large quantity. I called one supplier, and their tone cooled noticeably once they heard the volume. I moved on to another supplier who asked about the intended use and timeline, then quoted just as carefully as they would for a larger project. I still work with that supplier today—we've gone from a few thousand dollars to six-figure projects. The vendors who treat a $200 order with the same seriousness as a $20,000 order are the ones worth keeping.

Don't skip the site survey. Some suppliers offer a free preliminary survey at the quoting stage; some don't. Even if there's a fee, it's usually worth paying—ground level, access conditions, and drainage all look different in person than they do on a drawing.

Don't neglect internal communication cadence. I sent a weekly progress note to facilities and finance throughout this project. It felt like extra work at the time, but it gave me buffer room when quotes ran late or site acceptance hit snags—instead of being chased for answers at the last minute.

One last point that might seem to contradict the rest of this list: don't treat this checklist as a process where every step must be executed perfectly. I skipped steps during execution and doubled back on others. The point of a checklist is to know which steps you can't afford to skip—not to turn it into a track you can never deviate from.