Home Repair & MaintenanceMetal RoofingNew ProjectsHow to Install Metal Roofing Over Plywood

September 8, 2022by Joe0

Installing a metal roof over part of your home is an excellent idea; metal roofs are strong and reliable, but they are also low-maintenance when they are installed correctly. In most cases, you will be installing the metal on a plywood substructure. It’s important to protect this substructure as it can be costly and inconvenient to replace. Follow the best practice below for installation. 

Inspect the Plywood 

Installing a metal roof on your home is a sensible idea; it protects the wooden substructure in all weather conditions and reduces maintenance costs in the long term. The first thing to do is remove the existing roof and inspect the plywood underneath. Some of it might need replacing. 

Inspect the existing plywood and look for signs of rot and water damage. Chances are some sections will need to be replaced, but not all of them. If you replace sections of plywood, make sure it conforms to the standard of the American Plywood Association for quality assurance. 

If the plywood conforms to the commercial standards, it will include an APS stamp; this is important to have to ensure that the substructure is reliable. Once you replace the plywood, make sure it is free from dust, debris, and other contaminants, as well as pipes and protrusions.

Apply the Underlayment 

Between the outer metal layer of the roof and the plywood base, there is a sheet of protective material called the underlayment. This sheet is normally made from felt, asphalt, or polymer and is fundamental to the long-term success of your new roof. The underlayment is multifunctional.

The task of the underlayment is twofold; firstly, it protects the plywood from rotting and contamination; secondly, it directs water and precipitation away from the plywood in the direction of drainage. Talk to a professional about the best underlayment for the type of roof you need. 

Underlayment is very easy to install; all you have to do is roll out the covering on the roof and cut it to size with a roofing knife. When you have the correct size and dimensions, use half-inch roofing nails to secure the material to the plywood. This should provide effective protection.  

Apply Slipsheet 

A slip sheet is installed on top of the underlayment to protect it from tearing. If you intend to install a metal roof, you need to be ready for the expansion and contraction of the metal during different seasons. These changes can damage the underlayment and then the plywood. 

A slip sheet is made from rubber or plastic; it is installed on top of the underlayment and underneath the metal. Again, a slip sheet is easy to install; all you have to do is roll out the sheet and find the dimensions, then secure the sheet to the underlayment surface with nails. 

When the metal roof invariably expands and contracts in the winter and summer months, the underlayment and the plywood are suitably protected thanks to the slip sheet. This additional layer of protection keeps your roof dry and secure, reducing the cost of short-term maintenance. 

Install Roof 

Once you have prepared the plywood base and covered it with the underlayment and slip sheet, it’s time to start laying the metal panels and securing them with galvanized metal screws. Start at the bottom left side of the roof at the eaves and work your way along to the right-hand side. 

Make sure the metal panels overlap the roof and the eaves by one inch before securing them. When you have the base of the roof covered, it’s time to layer the sheets moving to the top. Each row of panels should overlap the previous one by twelve inches and be secured with screws. 

The metal panels should overlap each other by 12 inches to ensure there is no water leakage. Ensure this is the case whether you install the panels vertically, horizontally, or in combination. If the is any excess metal, cut it away using metal snips. 

Installing a metal roof on plywood is straightforward; it can be carried out successfully by anyone with some build skills or DIY skills. However, issues come up from time to time, so if you need some assistance, contact a professional for advice or hire a roof installation service.   

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RPS Metal Roofing & Siding, Inc is a manufacturer and distributor of metal roofs. Located in Welaka, Florida, our company has state-of-the-art manufacturing equipment resulting in fine quality metal roofs for commercial, residential and agricultural use.

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