How to do a metal roofing take-off

Metal roofing has been around for a while, but it’s still relatively new in North America compared to popular choices like shingles and shakes. However, the longevity, color options, and aesthetic appeal of metal roofing mean it’s fast becoming a favorite for residential and commercial buildings.

If you’ve never done a metal roofing take-off before, there are a few things you need to know.

Know Your Metal Roofing Cover Width

The first thing you need to know about metal roofing take-offs is the cover width of the metal roofing profile you will be using. This is usually less than the sheet width because you will need to overlap the sheet on each of the vertical sides to ensure that your roof is watertight.

You will need to know the eave side length of each section of your roof as well as the cover width of the metal roofing material to calculate how many sheets you will need for that part of the roof.

Calculate Your Sheet Length

If you’ve been in the roofing business for a while, you probably already know how to calculate the actual height of each section of the roof on a building using the roof pitch.

You can use Pythagoras to do this, or in roofing terms, √(rise2 + run2).

If you have access to the roof itself, rather than calculating your roof material off a roof plan, you can also measure the roof to get your sheet length, but make sure you allow for any overhang you might have at the eaves.

Calculating sheet length is important to ensure you don’t waste material, but it also helps prevent unnecessary cutting. Not only does cutting metal roofing add to labor costs, but hot metal shavings or “swarf” can damage the surface of metal roofing. So you want to avoid cutting on-site as much as possible.

Don’t Forget Accessories and Hardware

The last thing you need to do before you do a metal roofing take-off is find out what kind of accessories and hardware you need for your roof.

Some metal roofing systems, like concealed fix and standing seam systems, use hidden clips and nails, but others might use special kinds of screws.

You will probably also need to purchase a variety of hip flashings, valleys, apex flashings, and drip flashings for the various features of your roof, and many of those are attached using rivets or nails.

Finally, metal roofing often requires various kinds of sealants and adhesives, which might include silicone and mastic products, depending on the type of metal roofing and the installation method you are using.

Always Ask the Manufacturer

Over time, you will become familiar with all the types of metal roofing and their installation methods, and doing a metal roofing take-off will become second nature, but until you do, the best source of information is usually the roofing manufacturer.

Most metal roofing manufacturers will have data sheets and installation guides that will help you figure out exactly what you need to install your roof properly, and they’re a great resource to ensure you account for everything in your roofing estimate.