When deciding on a new metal roof, one factor that most completely overlook is the weight! Although it is rare, we have seen roofs collapse due to the amount of weight. This is a very important topic when you are interviewing roofing companies as many will try to save themselves money by being dishonest with you. So, how do we calculate what is a safe weight for the metal roof?

Calculating The Weight Of The Metal Roof

There are so many different metal roofing options, and those options play the largest part in calculating the weight of the metal roof. The main items to consider are:

• Metal Roofing Type
• Thickness Of The Metal Roof (What gauge)
• The length and Width Of The Panels/Shingles

Dangers To Consider Regarding The Weight Of The Metal Roof

One of the biggest mistakes we see is a homeowner and/or a roofing company installing over the existing roofing system.

Can you do it? Yes, you can!

Should you do it? Absolutely not.

In all of our roofing replacements, we remove the entire roofing system to inspect everything down to the wood decking while also removing all the stress to the frame of the house. When you add a metal roof over shingles for example, you are adding more stress to the entire frame which can lead to problems down the road. Always remove the old roofing system before installing your new metal roof so the weight is not ever a factor.

When you are factoring your weight limits, don’t forget to account for snow storms which can triple the weight of your roof overnight.

The weight of this roof was too much and it collapsed. Always do what you can to keep weight off the roof.

Weight Of Each Metal Roofing Type

This list is in order. I am going to start from the lightest to the heaviest metal roofing material. It is important to note that the below numbers do not account for any other roofing material or decking. This is only for the metal product being used on the roof.

Weight Of Aluminum Roofing

By far the lightest of all the roofing materials. We love working with this type of metal roof because it is so light it is east to install, does not have much safety risk and almost adds to real weight to the roof.

On average, the weight of an aluminum roof is 0.75 pounds per square foot. This is crazy light when you consider your normal asphalt shingle roof has a weight of almost 3 pounds per square foot.

Weight Of Copper Roofing

Copper is also a great choice regarding weight and lasts a long time. The only real issue with this metal is the price.

On average, a copper roof weighs about 1 pound per square foot.

Weight Of Corrugated Roofing Systems

We are asked about this a lot actually from some of our government clients who absolutely love this product due to it’s longevity. But make no mistake about it, this is a heavy roofing system. Do not install this without removing the old system first.

On average, a 26-gauge,  Corrugated Roof weights 3.5 pounds per square foot.

Weight Of A Zinc Roof

We have actually never installed a zinc roof as these are not very popular in our area or with our clients. To get the weight calculations we reached out to some zinc roofing manufactures and asked them.

On average, a zinc roof weighs about 1.5 pounds per square foot. 

Weight Of Stainless Steel

Stainless steel is one of the strongest metal materials and is also one of the most expensive and long lasting.

The weight of A Stainless Steel roof is around 2 pounds per square foot. It is very heavy and hard to work with.

Calculating The Weight Of The Metal Roof

Now, you need to know the square footage of your roof (and we wrote this article to show you). But once you have the square feet, you just need to multiply that by the metal roofing material.

The average roof size is 1,700 square feet or 17 squares.

So, using our numbers from above…

• Aluminum: 0.70 pounds per foot X 1,700 feet = 1,190 lbs
• Corrugated Steel: 3.5 pounds per foot X 1,700 feet = 5,950 lbs
• Stainless Steel: 2 pounds per foot X 1,700 feet = 3,400 lbs
• Copper: 1 pound per foot X 1,700 feet = 1,700 lbs

Benefits Of A Heavy Roof

I’ve scared you enough with how dangerous a heavy roof can be, but there are some advantages as well. But note, these advantages DO NOT outweigh (no pun intended) the disadvantages.

• A heavy roof is thicker which means it helps reduce metal roof noise.
• A heavy metal roof will last longer than a lighter metal roof.

Closing Thoughts

The weight of your new metal roof should not be a problem as long as you are removing your old roofing system completely. If you are going to install a new metal roof over your existing shingles I ask that you spend a lot of time making sure you are not putting your entire house at risk due to the extra weight.