Roofing shingles are overlapping pieces that are often flat and laid in consecutive lines over the whole roof. The purpose of shingles is to create a watertight and wind-resistant seal that protects your house from the outside elements. An incorrectly installed shingle can come undone completely in a gale of wind or when tornadoes hit.

Installing metal roofing over shingles gives it that extra bit of protection and security. It’s also great for preserving your current shingles because they will be installed on top of the existing roof. Read on to understand how to install metal roofing over shingles.

Assess the Current Steel Shingle Sheets

Before installing any roof over a steel shingle sheet, you need to assess if there is any current damage such as roof leaks or rotten roofing panels. Any damage, even if it’s minor, will mean that you may need to reinstall the roofing again in a few months.

Look for signs of water damage and if any weighting issues have caused buckling or sagging in the roof. You may need to climb into the ceiling to make sure that there is no structural damage.

Specific Manufacturers and Warranties

Generally, a good roofing installation will last for 40 or 50 years, but when the time comes to contact the manufacturer, they may not be available anymore. The roofing itself will also depreciate as the years go on, so you will have to keep up regular maintenance to keep the roof in good condition.

This is where spending a little bit more can be to your advantage. You may spend an extra $10,000 for a good contractor but you won’t have to repair the roof as often. You also get extended warranties on the more expensive products you use.

Screws and Bolts

There are specific screws that need to be used for metal roofing, just as there are particular places where you install the roof. Screws need to be tightly fastened to the flat part of the shingle steel and not the rib. This will avoid any unnecessary lifting between the plates that will allow water to enter and cause damage to the structure of the roof.

Did you know that it’s not wise to use nails anymore, but rather specific screws for metal sheeting? You also need to make sure they are placed between 24 and 30 inches apart. You should also skip all the ribs of the steel shingle and only place screws in the current holes. This way, you won’t need to worry about creating more screw holes that just look bad.

Safety Regulations

Anytime you take on a home or roof repair job such as this, it’s important to wear the right safety uniform and use newer tools that won’t break. You will want the best of the best when it comes to your physical safety and the strength of the metal roofing over your steel shingle roof.

Make sure that you wear a harness in case you fall off the roof. You will also need proper safety gloves that can withstand heat and won’t wear away quickly. If there is a lot of wind, it might be a good idea not to install the metal roof until it quietens down. Steel and metal are heavy, and if the wind knocks it in your direction you could be knocked out, or worse, thrown off the roof completely.

Vapour Barriers

Installing a metal roof over a steel shingle will cause condensation. No matter how small the space is between the two roofing materials, condensation will still creep in and can be detrimental to the integrity of the roof. If you choose not to take the shingles off, be sure to put down felt paper before you install the metal sheets. These vapor barriers are essential when working with different materials, and it increases the likelihood that the metal roofing will stay intact for longer.


You can have the best installation of metal roofing in the world but, if it looks bad, you won’t be happy. The trimmings are the most important part of the aesthetics and can also prevent rain, wind, and snow from getting inside. Each trim should be wrapped with flashing around all the sides of the roof that overhang.

Other necessities would be an ice guard that can protect your gutters when it snows. The best way to get the trim looking great is to have someone look at it from the bottom. This helps to ensure that it’s equal, straight and that no important bits of the roof are left open.

Shingle roofing is much cheaper than metal roofs, but the long-term value is probably not worth it. With metal roofing, you get better durability and metal roofs can withstand almost anything Mother Nature has to offer.