Steel Building Snow Removal and When the Roof Needs It

A foot of wet snow sits on your shop roof, the forecast promises another eight inches, and you are standing in the yard wondering whether to climb up there or leave it alone. Pick wrong in one direction and you risk a buckled purlin. Pick wrong in the other and you put a shovel through the paint, or yourself off the eave. Steel building snow removal is mostly about knowing when the roof actually needs help, and the honest answer is less often than people think.

Most storm damage I see on roof walks comes from owners who never checked their load numbers, or who attacked a safe roof with a steel shovel.

Start with the snow load on your drawings

Every engineered steel building has a design roof snow load printed on the stamped drawings, usually in pounds per square foot. In much of the Midwest you will see 20 to 30 psf. Mountain and northern lake country buildings often carry 40 to 70 psf or more. That number is your budget. Snow removal only matters when what is on the roof gets close to it.

Here is the part people skip: snow weight varies wildly. A rough guide for one foot of depth:

Two feet of powder on a 30 psf roof is fine. Eighteen inches of rained-on snow is not.

A quick weight check you can do from the ground

Cut a 12 by 12 inch square of snow from an open spot near the building, at full depth, using a cake pan or a cut-down bucket. Melt it and weigh the water in pounds. That weight, roughly, is the load in psf for that depth. A kitchen scale and ten minutes give you a real number instead of a guess.

Where snow actually loads up on a metal roof

Uniform load across the whole roof is rarely the problem. Drifts are. Watch these spots after a windy storm:

• Lean-to roofs and lower roof steps. Snow slides off the main roof and piles onto the lower one. A lean-to designed for 30 psf can see double that in a heavy slide.
• The leeward side of the ridge. Wind strips one slope and dumps the snow on the other, creating a drift that can be three times deeper than the windward side.
• Behind parapets, rooftop units, and against a taller adjoining wall. Anything that stops wind creates a pocket.
• Valleys between roof sections. These collect snow and meltwater, and then ice.

Low-pitch roofs, 1:12 or under, shed snow poorly and hold the most. A 3:12 or 4:12 roof with a slick painted surface often clears itself within days of sun.

Warning signs that mean act now

If you see any of these, get people out of the building first and then deal with the snow:

• Walk doors or roll-up doors that suddenly bind or will not close.
• Popping, cracking, or creaking sounds from the frame, especially at night as temperatures drop.
• Visible sag in purlins or girts from inside, or a ceiling liner that bows.
• New leaks at the sidewall or around fasteners, which can mean panels are flexing.

How to do steel building snow removal without damaging the roof

When the numbers say it is time, work from the ground if you possibly can.

1. Use a roof rake with a plastic or rubber blade. Telescoping models reach 20 to 24 feet and cost 60 to 150 dollars. Metal blades scratch through the paint and the coating, which invites rust at every gouge.
2. Leave 2 to 3 inches on the panels. You do not need to scrape to bare steel. That last layer protects the finish, and the load it adds is tiny.
3. Remove snow evenly from both sides. Clearing one slope completely while the other carries a full load creates the unbalanced condition the frame is least happy with. Work in strips and alternate.
4. Clear drifts first. Start at the lean-to or the deepest pocket and work toward the lighter areas.
5. Pull snow down the slope, never across ribs. Dragging sideways catches fastener heads and can lift screws or tear washers.
6. Keep the drop zone clear. Snow sliding off a metal roof comes down fast and heavy. Keep vehicles, people, and gas meters out of the way.

Never chip at ice with a shovel or axe. You will punch a hole before you free it. Let it melt or call a crew with steam equipment.

When to call a crew instead

If the roof is over 14 feet at the eave, the pitch is steeper than 4:12, or there is ice anywhere under the snow, hire it out. Commercial snow removal crews in my area charge around 75 to 150 dollars an hour per worker, or a flat 300 to 1,200 dollars for a typical 40 by 60 shop depending on depth.

The common advice I disagree with

You will hear people say "clear your metal roof after every storm." I think that is bad advice for most well-engineered steel buildings. Every trip up there risks a fall, scratched coating, and loosened fasteners, and raking a few inches of powder off a 40 psf roof only wears it.

The better habit is to know your design load, weigh the snow when a storm looks heavy, and clear only when the load climbs past about 70 percent of the rated number or when drifts form. Most winters, that means touching the roof once or twice, or not at all. Snow on a steel roof is not a problem by itself. Snow beyond what the engineer planned for is.

After the snow: what to check in spring

Once the roof clears, inspect it from a ladder for raking scratches, backed-out screws, crushed ridge caps, and bent gutters. Touch up bare-metal scratches with matching paint and replace any screw with a torn washer. If you noticed a drip during the thaw, track it down with the steps in our guide to finding a steel building roof leak before it spreads.

Fold this into your yearly routine rather than treating it as a one-off. Our maintenance schedule that actually protects a steel building puts the post-winter roof walk right where it belongs, and you can find more upkeep guides in the maintenance and repairs section.

Frequently asked questions

How much snow can a steel building roof hold?

It depends on the design snow load on your stamped drawings, commonly 20 to 70 psf. A foot of dry powder may weigh 5 psf, while a foot of wet snow can weigh 20 psf. If your drawings are lost, ask the manufacturer using your order number.

Should I remove snow from my metal building roof?

Only when the weight approaches the design load, when drifts build up on lean-tos or lower roofs, or when you see warning signs like binding doors or sagging purlins. Many steel roofs with a decent pitch shed snow on their own. Unnecessary clearing causes more damage to coatings and fasteners than it prevents.

What is the best tool for removing snow from a steel roof?

A telescoping roof rake with a plastic or rubber blade, used from the ground, is the safest choice for most owners. Avoid metal shovels and anything with a sharp edge, which cut through the paint and coating. Leave a thin layer of snow on the panels to protect the finish.