3 Common Questions We Get Asked About Metal Roofing Installation


For many general contractors, metal roof installations can be a beneficial area to gain experience. As you start to learn more about the process, you may have a couple of questions.  Here, we are going to answer the three most common questions we receive; how to put a metal roof over shingles, where to place screws on a metal roof, and how to paint a metal roof. 

1. How to Put Metal Roof Over Shingles? 

Applying a metal roof over the existing shingles is a great way to save time and money. While it is a realistic possibility for some, it will not be compatible with every roof. To evaluate the roof and ensure it is fit for this kind of installation, you will need to closely examine the shingles for any leaks or damages. If any are found, the old roof will need to be completely removed and replaced. Second, examine the shape of your roof. Metal panels will not attach to the roof correctly if it is unbalanced. The final aspect to consider is if the roof already has multiple layers. If there is more than one roof on the building, the new metal roof will not be able to attach properly. 

When installing a metal roof over shingles, panels are your only option. A pre-existing roof prevents metal shingles from attaching properly. When you are planning a metal roof installation over an old roof, you will need to ensure that the space between the two roofs is properly ventilated. If moisture is present, it can create major problems in the future. The underlayer of the roof could begin to rot and compromise the overall structure. Installing a ventilated metal roof may be the best option to have peace of mind about water vapor being able to escape. 

2. Where to Place Screws on Metal Roofing? 

Anchoring your metal panels or shingles is imperative to complete a successful roofing installation. To ensure that the roof is leakproof and secure, screwing your roof is one of the most important steps in the metal roof installation process. Metal screws are durable and will not be prone to bending like nails. As your roof naturally expands and contracts, your fasteners will need to stay in place without shifting.

When it comes to installing the screws, placement is key. To ensure a tight seal, screw your roof down inside the top panel. When the screw is installed on top of the rib, it can cause the screw to tilt, creating a bigger hole and an opening for moisture. If it is placed at the top of the rib, security could be compromised. Installing the screw inside the top panel, in between the ribs, will help prevent the screws from being ripped out during strong storms or winds. 

Type of Fasteners 

There are two types of fasteners you can use to secure your roof; standing seam and exposed. While both serve the same purpose, they have different advantages and require unique installation. 

Standing Seam 

These are also known as concealed fasteners and hide the fasteners from view once the metal roof installation is complete. By fastening the roof down under the metal panels, it creates a more uniform appearance. Additionally, no hardware or screws will be accessible from the surface, creating an extra layer of durability and security. Installing a standing seam metal roof is completed by laying a panel over the roof and then locked into place by a fastener clip. 


Meanwhile, exposed metal roofs leave the hardware visible once the installation process is complete. The installation process is more straightforward than a standing seam installation and does not require any special tools. Exposed fasteners are often less expensive due to the easier installation. 

3. How to Paint a Rusty Metal Roof? 

Metal roofs are a great option for many people due to their long-lasting durability. However, that does not mean it is exempt from any wear and tear that can happen over time. If it is possible to repair the roof instead of completely replacing it, adding a new layer of paint can make it look good as new. Since most metal roofs are made out of steel, copper, or aluminum, they receive a special coating to prevent rust. Over time, the coating can begin to thin and patches of rust can appear. In order to keep the metal roof from obtaining any harsh damage, repairing and repainting your metal roof is essential. While it would be convenient to just slap a layer of fresh paint onto the rusted roof, it is not that simple. To ensure that the roof lasts for many years to come, removing the rust and adding protective primer are essential. 


As a general contractor, you know that any time you are on a roof, you should take safety precautions. This holds true when you are painting a metal roof. Ensuring that you are secure with a harness and safety rope will help keep any unforeseen accidents at bay. The first step in repainting your roof is to make sure it is clean and the old layer of paint has been removed. Use a putty knife to remove any remaining patches of paint so your new layer can go on smoothly. Be sure to be cautious during this step. Gently removing the paint will ensure you do not damage the metal panels underneath. Once you are finished scraping, wash off any remaining chips or debris and let it dry for a couple of hours. 

Once your roof is ready for the layering process, remove any rust by scraping the panels with a wire brush. Wipe away any flakes and spray a thin coat of primer that will prevent rust from reforming. If there are any holes in the roof, they must be patched and prepped before the layer of paint is applied. For every hole, you will apply roof cement to the edges and smooth it out until the surface is even. Then, cut a piece of acrylic mesh that is 1 inch larger than the diameter of the hole. Add a second layer of cement and mesh. Finish it off by adding another layer of cement to create a watertight seal. 


After the roof has been prepped, and there are no remaining holes or cracks, you can begin the painting process. You will need to apply a layer of primer that is designed for metal roofs over the panels and areas that you patched. Once the primer is dry, you can begin painting with an airbrush or roller. Adding a second coating will ensure durability and create a seamless finish. 

Picking the right kind of paint is important to ensure that it will stick to the roof. Many metal roofs will pair well with an oil-based or acrylic-acid paint. Paint features such as UV reflection, water resistance, and insect repellant can advance the protection of your metal roof. 

Builders Materials Checklist

For any metal roof installation, it is important to closely evaluate your work to ensure it is done correctly and obtain the right materials. If you are not prepared ahead of time, you can delay the installation by having to gather any missing supplies. Download our free Builder Materials Checklist for Contractors to stay on track with your next project.

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