Why Change Orders Happen and How to Keep Them Off Your Project

A change order rarely shows up out of nowhere.

By the time one lands on your desk, the problem behind it has usually been sitting there for weeks: a measurement that wasn’t quite right, an equipment submittal nobody reviewed closely enough, or an airflow opening that didn’t line up the way everyone assumed it would.

At Curbco, we’ve worked alongside contractors, distributors, engineers, and facility teams on thousands of RTU replacement projects. The pattern is consistent: many avoidable change orders can be traced back to information gaps that existed before the crane ever showed up.

This guide walks through where change orders typically originate on RTU replacement projects, what they actually cost beyond the invoice, and the planning steps that can help keep them from happening in the first place.

Relax… It’s Curbco.

Figure 1: Where change orders typically originate on an RTU replacement project: before, during, or after installation.

What Actually Triggers a Change Order?

Many change orders on RTU replacement projects can be traced back to issues such as:

• Field measurements that don’t match what was ordered
• Roof curb conditions discovered after demolition begins
• Equipment substitutions made late in the process
• Airflow or utility connections that don’t align with the new unit
• Structural conditions that weren’t reviewed ahead of time
• Incomplete or outdated project drawings

None of these situations are unusual. What matters is when they’re discovered.

Caught during planning, there’s often time to make an adjustment. Caught on the roof, the same issue can become a change order.

The Real Cost of a Change Order

The line item on the invoice is only part of it.

A single change order can also mean:

• A crane sitting idle while a solution is worked out
• A crew reassigned to another job while they wait
• A delayed occupancy or reroof schedule
• Renegotiated terms with the building owner or GC
• Lost trust between trades on a project that was supposed to be routine

On a tight schedule, the cost of a change order is rarely just financial. It’s the ripple effect across everyone else who was counting on that installation date.

6 Ways to Keep Change Orders Off Your Project

Figure 2: Six planning checkpoints that can help reduce RTU replacement change orders.

1. Verify Field Conditions Before Equipment Is Ordered

One of the most common sources of avoidable change orders is a measurement taken once, assumed to be correct, and never double-checked.

Before ordering replacement equipment, confirm:

• Roof curb dimensions, inside and outside
• Curb height and roof pitch
• Supply and return opening locations
• Condition of the existing curb structure

If field verification isn’t practical for your team, a second set of eyes can help catch details a single visit might miss.

👉 Not able to get accurate field measurements yourself? [Learn about our Curb Measurement Service].

2. Review Equipment Submittals as Early as Possible

Two units with the same tonnage can still have different footprints, weights, airflow layouts, and curb requirements.

Reviewing manufacturer submittals early, rather than after equipment has already shipped, gives your team more time to identify mismatches while there’s still room to solve them without disrupting installation.

📄 Ready to move forward? [Submit Your Drawings] for engineering review.

3. Use a Custom Curb Adapter Instead of Assuming a Fit

One of the biggest change-order risks is assuming an existing curb will work with new equipment without confirming compatibility.

A custom curb adapter is designed to bridge the differences between the existing roof curb and replacement equipment, including differences in footprint and airflow configuration.

That means your team can address compatibility during planning instead of trying to solve it on installation day.

➡️ [Explore Curbco Custom Curb Adapter Solutions].

4. Confirm Airflow and Utility Alignment Before Production

A unit can fit the curb and still create installation problems if the supply, return, or utility connections don’t align as expected.

Before production begins, review:

• Supply and return opening dimensions
• Opening locations and offsets
• Duct alignment
• Utility connections
• Economizer compatibility

Confirming these details early can help reduce field fabrication and last-minute modifications.

5. Build Lead Time Into Your Schedule

Compressed schedules can create pressure to substitute equipment, skip verification steps, or move forward based on assumptions.

Building realistic lead time into the schedule for the RTU, curb adapter, freight, and crane gives your team more room to identify and address problems before they affect installation.

⚡ Working against a tight deadline anyway? [Ask about FastPass] for expedited production on qualifying projects.

6. Keep Every Trade Looped In Early

Change orders often surface at the seams between trades, where one team’s assumptions don’t match another team’s plans.

Bring the right people into the conversation early, including:

• HVAC contractors
• Roofing contractors
• Electricians
• Structural engineers
• General contractors
• Equipment and curb suppliers

Early coordination can help prevent a decision made by one trade from creating additional work for another.

How Curbco Helps Reduce Change-Order Risk

A change order can be a sign that a project moved forward on an assumption instead of a confirmed detail.

That’s the gap we’re built to help close.

Contractors, distributors, and engineers rely on Curbco for:

• Engineering review of project drawings and submittals
• [Custom Curb Adapters] designed around confirmed project conditions
• [Curb Measurement Service] when a second set of eyes is needed
• Expedited production through [FastPass] when schedules are tight
• Project tools through [KurbHub] to help simplify the ordering and project process

Whether it’s one rooftop unit or a multi-site retrofit program, our goal is the same: help your team confirm the details before installation day, so there are fewer surprises on the roof.

Relax… It’s Curbco.

Ready to Keep Your Next Project Change-Order-Free?

Before requesting a quote, gather:

• Existing unit model number
• Replacement unit model number
• Roof curb dimensions
• Rooftop photographs
• Equipment submittals
• Project drawings

The more complete the information, the easier it is for our team to understand the application and identify questions before production.

📁 [Submit Your Drawings] and our team will review your project.

Need it sooner?

⚡ [Ask about FastPass] for expedited production on qualifying projects.

Related Resources

Continue planning your retrofit with these Curbco guides and tools:

• [Complete Guide to RTU Replacement Projects]
• [How Contractors Measure Existing Curbs Before RTU Replacement]
• [10 Common Rooftop HVAC Retrofit Mistakes (And How to Avoid Them)]
• [Curb Adapter vs. Roof Curb: What’s the Difference?]
• [Custom Curb Adapters]
• [Curb Measurement Service]
• [KurbHub]

Relax… It’s Curbco.