Getting an accurate measurement for your metal roofing panels may seem like a no-brainer, but it’s not quite as simple as lengths and widths. The many complexities of a roof must be taken into consideration to ensure your numbers add up. For instance, anything that intrudes upon a roof plane needs to be included in drawings with labeled measurements as these conditions will all affect the measurement but are sometimes overlooked.

Here are some specific conditions to consider before getting out the measuring tape as well as some tips for installers.

Building Conditions to Consider Before Measuring

The type of roof system

Is it going to be a standing seam roof system or an exposed fastener system? Once you’ve decided on your roof type, review all the conditions and details on the roof. If it’s a standing seam roof, will the roof system need to float? If so, where will it be pinned, and what direction will it float?

Review installation technical manuals for installers and erectors to familiarize yourself with how to adjust for ridge conditions, end lap conditions and more.

Is it a new or existing metal building?

If it is an existing building, are there new or updated building codes to consider? This could possibly dictate panel type, gauge, or width, or require additional framing members that could impact the final measurements.

What is the purlin spacing?

The panel break at the purlin for an end lap condition will need to be considered.

Are there extensions, overhangs, or penetrations?

Include any roof extensions or overhangs that may not be apparent at first glance. All roof conditions should be considered when calculating panel and trim length, including any roof penetrations such as pipes, roof curbs, skylight hatches, etc.

The manufacturer’s details will aid in determining such things as panel hold back at the ridge, or panel overhang at the eave or gutter. Also, roof or slope transitions, and panel hems should be considered.


The thickness of the insulation could determine or dictate the fastener type used.

Measuring Tips

  • Field verify the roof slope. The contractor should gather the field dimensions and measure when the framing is in place. While you can measure off a set of plans, things can change in the field. 
  • The structure should be square while you’re measuring. Scaling from plans may get you close but measuring erected framing that is plumb and square is the most accurate. 
  • Measure multiple spots for verification.
  • It’s always a good idea to use a plan view of the roof or sketch a bird’s eye view to record your measurements.
  • Record your measurements in the units of measure that your manufacturer uses, typically feet and inches, to avoid errors. 
  • The erector may elect to add a few inches to the length of the panels at a hip or valley to remedy any cutting mishaps since these panels will be field cut to the hip or valley angle.
  • Some contractors include one or two extra panels at the longest length for any errors or jobsite damage.

Ultimately, the takeaway is that any differential when measuring metal panels for installation could affect a building’s performance. It’s important to keep all potential scenarios that could affect measurement accuracy in mind throughout the entire process. To find out more about the proper way to measure a roof for metal buildings or to schedule training, contact a team of experts with a metal panel manufacturer.