How to install metal roofing over plywood? (2024)

Can metal roofing be installed over plywood?

The longer answer is that when metal roofing is installed, it is always best to use a roofing felt layer between the metal roofing and the bare plywood. This should always be used as a bare minimum, but some people also choose to add an extra layer with a slip sheet that can also help safeguard the felt sheet.

Do you have to put plywood under metal roof?

Some might choose to skip using underlayment to save money. However, the metal roof underlayment acts as an added layer of protection. You can save money by using underlayment because it will help you avoid problems that would need to be fixed. The short answer is yes, your metal roof does need underlayment .

Do I need furring strips under metal roof?

It is not recommended to install metal roofing over shingles without furring strips. The thermal expansion and contraction of the metal will rub against the shingle granules and the metal will corrode from the underside. The gaps introduced by furring strips also allow air venting which can reduce moisture.

Can you put metal roofing directly on OSB?

Metal roof screws have very aggressive threads, and OSB holds a screw as well as solid lumber (though obviously it's thinner). Any wind that pulls them out will do much more than that. I wouldn't hesitate to do this.

What is the best underlayment for metal roof?

30# felt underlayment (or two layers of 15# felt) are recommended for metal roof panels. Felt is an all-over roofing accessory made of a natural (wood cellulose, natural fibers, etc.) or synthetic (polyester or fiberglass) base that is then saturated in asphalt to make it water-resistant.

Should you put plastic under a metal roof?

Most metal roof companies recommend installing felt paper on roof sheathing before you install the metal roofing. The asphalt in the felt paper is waterproof and does a great job of protecting the untreated wood roof sheathing. I would not install plastic on the sheathing because it's a vapor barrier.

Do you need a vapor barrier under a metal roof?

Without one, water can get trapped in the wall, which will produce moisture and ultimately other issues like rot, mold, and trouble with thermal performance. Vapor barriers are recommended for under metal roofs.

Is tar paper needed under metal roofing?

Yes, metal roofing absolutely needs underlayment.

Felt and synthetic underlayment are great options for asphalt roof systems.

How thick should plywood be for metal roofing?

The important numbers to glean from this are the thickness—you should use plywood that's at minimum 15/32 inches thick—and the span rating—which you'll want to make sure matches your other plywood boards, especially if you're doing any repairs or replacements.

Do you screw metal roof on ridge or flat?

And the fact of the matter is that most U.S. metal roofing manufacturers say you should put screws into the flat, because this location offers a solid wood surface just beneath the metal panel, resulting in a safer, tighter, more secure seal.

How much should a metal roof overhang?

​ Be sure that the panels are properly side lapped to ensure a water tight seal. 3: The panels at the eave side of the roof should overhang into the gutters 1 to 1-1/2 inches. If installing metal on a non gutter application you can overhang the panel up to 3 inches.

Do you need to put anything under a metal roof?

Underlayment is the layer beneath your roofing system that serves as an extra weather resistance barrier, ultimately providing greater moisture protection. But this layer of protection isn't optional; it's really essential to a proper metal roofing system.

How far apart should furring strips be for metal roof?

Factors for Determining the Spacing of Furring Strips on a Metal Roof. As a general rule, furring strips are usually spaced somewhere between 12 inches to 24 inches apart.

Can you spray foam directly under metal roof?

absolutely! Some building owners don't realize that spraying over metal is an option. If you have a roof leak with your metal roof, installing spray foam over top can close all those leaks and provide you with more R-value. In fact, spray foam has a 100% chemical adhesion across the entire metal roof.

Can Tyvek be used under a metal roof?

DuPont Tyvek Protec 120 Roof Underlayment is an engineered synthetic roofing underlayment with industry-leading walkability. It is ideal for slopes 2:12 or higher and can be used under a variety of roofing materials, including asphalt shingles, cedar or metal roof cladding.

Can you put foam under a metal roof?

Yes. Spray foam insulation can be applied to metal panels on open decking systems after the metal panels are installed, provided the following care is taken: Thermal spacers must be used on all metal purlins/framing to prevent rust or uneven color.

Is it hot under a metal roof?

A common misconception is that metal roofs become hot in the summer and create an overheated living space because metal quickly heats up to the touch. However, this is a myth. Metal roofs do not make a house hotter than any other kind of roofing material.

Does a metal roof need to breathe?

Like other types of roofing, metal roofing needs to breathe. Metal roofs use static ventilation, which promotes natural airflow. In other words, it doesn't need to rely on fans or other methods to allow for proper air movement. Having the right roof ventilation in place at the time of installation is key.

How do you vent under a metal roof?

Ridge vents are the most popular option for metal roofs and are an effective way to achieve proper attic ventilation. Ridge vents are installed at the ridgeline of the roof and run continuously along the entire span of the roof. The Razorback Ridge Vent is installed along the bottom of the ridge cap on either side.

What happens if you don't install vapor barrier?

Vapor barriers can often double as added insulation, protecting buildings against excess cold and heat. Failure to use a vapor barrier can lead to higher energy costs and an ideal environment for mold and mildew growth.

How do you keep a metal roof from condensating?

Properly Insulate the Attic

Thankfully, finding a solution to metal roof condensation in the attic is straightforward; you simply need better insulation. Sufficiently insulate your ceilings to create a barrier between both sections of the house, preventing air leaks and metal roof condensation successfully.

Do I need an air gap in roof?

It is important that air is allowed to circulate between the roof covering and the insulation to avoid condensation - a gap of at least 50mm (2 inch) must be left between the insulation and the inside of the roof covering.

What roof underlayment is best?

Synthetic Underlayment

This is currently the most popular choice for roof underlayment, and with good reason. Made with an asphalt-saturated basemat and fortified with a mix of fiberglass, this product is not only extremely water-resistant, much stronger and more resistant to tears than other types of underlayment.

Which is better felt or synthetic underlayment?

Synthetic underlayment lasts longer than traditional roofing felt, which makes it a better investment for homeowners. It's also more water-resistant, which means greater protection for the roof deck should the primary roofing material fail.

What can I use instead of tar paper?

The classic type of roof underlayment is known as asphalt-saturated felt. It's similar to tar paper, except that instead of tar, the waterproofing ingredient is asphalt.

Can you walk on 26 gauge metal roofing?

While the answer is yes, you can walk on a metal roof, our team never recommends it. There are a lot of factors that come into play that deal with your own safety and protecting your roof from damages caused by walking around on it. However, we know that sometimes you have to in certain scenarios.

Do you need purlins for metal roof?

When it comes to roofing, metal purlins are a critical element needed to give the structure proper support. Though we do not do installations ourselves, Western States Metal Roofing has been providing contractors with the materials required for a successful installation for over two decades.

Can you glue down metal roofing?

Modern roofing companies are now using this tried-and-true technique to attach roofs with concealed fastener systems. The benefits of using adhesives for metal roofing are many, including the elimination of screw holes, reduced installation time, elimination of oil-canning, dimpling and more.

Should I screw or nail metal roof?

In most instances, screws will turn out to be marginally better than nails when it comes to this, and so should be one of the first choices you make when the time comes. One of the main reasons why screws are better than nails at metal roof construction is the fact that they tend to hold for much longer.

What angle should a metal roof be?

When installing a metal roof, you will notice that the manufacturer recommends a minimum pitch of 3”/ft. This means that the roof should slope downward by 4” for every single foot of horizontal distance.

What is the biggest problem with metal roofs?

If water accumulates anywhere on the roof because of poor-quality installation or repair, it can eventually cause serious damage. Low-grade metals may also be thinner gauge and less durable. Some metals rust in certain climates or dent more easily than others during hailstorms or installation.

Are there any disadvantages of a metal roof?

Metal roofs can fade in time or may be susceptible to staining. If not installed correctly, metal roofs can fail at the seams. It's essential to have a metal roof installed by a qualified, experienced contractor. Metal roofs are considerably more expensive than most other options.

How often should metal roofing be screwed down?

We recommend that if you have an exposed fastener metal roof, it's best to get it checked every ten years or even sooner. It's very likely that in 10 – 15 years your exposed fastener metal roof is going to need a re-screw.

Do you need drip edge with metal roof?

Drip edges on metal roofs are essential components for keeping water away from the home's structure. Installing drip edges can provide additional protection from wind damage, as it helps create an overlap between panels that can prevent wind uplift.

Is a drip edge necessary on a roof?

Without a drip edge, water may end up beneath the shingles and may cause damage to various parts of the home. Though your home may not have originally had a drip edge installed, drip edges are now required by most building codes across North America to protect homes from damage.

Do you have to take shingles off a roof to put a metal roof on?

Metal roofs can be installed over your existing roof without tearing off shingles, provided local building codes allow it. While shingle removal is the preferred route, tear-off is messy and raises the cost of the job. A potential problem with this type of installation is trapped water vapor.

What kind of wood do you use under a metal roof?

The reaction to the chemicals in the wood and copper which is a dissimilar metal cause the metal to rust. It is recommended that you always use untreated pine or spruce stringers to attach the metal to.

How many nails do you get from a furring strip?

Yup, used adhesive as well, and only two nails per strip.

Can I screw metal roofing directly on plywood?

The longer answer is that when metal roofing is installed, it is always best to use a roofing felt layer between the metal roofing and the bare plywood. This should always be used as a bare minimum, but some people also choose to add an extra layer with a slip sheet that can also help safeguard the felt sheet.

How long does a screw down metal roof last?

Longevity. Metal is long-lasting - so long-lasting, in fact - that a standing seam metal roof can last up to 50 years, while a screw-down metal roof may last 30 years. How does that compare to a standard roofing material like asphalt shingles? You can expect a typical asphalt shingle roof to last approximately 20 years ...

Why do screws back out on metal roof?

Thermal expansion and contraction of the metal roofing, and possibly movement of the substrate, can cause through-fasteners to loosen or back out over time. Metal roofing with loose or missing fasteners will suffer reduced wind resistance and possible moisture intrusion.

Does anything go under metal roofing?

Yes, metal roofing absolutely needs underlayment.

Felt and synthetic underlayment are great options for asphalt roof systems.

Can metal roofing be installed over treated lumber?

Pressure treated wood does not work well with metal. The reaction to the chemicals in the wood and copper which is a dissimilar metal cause the metal to rust. It is recommended that you always use untreated pine or spruce stringers to attach the metal to.

Does metal roof need moisture barrier?

To avoid condensation buildup with your metal roof, you will need to have a moisture barrier in place. When the air in the home is warmer than the air outside, condensation will collect. If the roof system is not ventilated properly, condensation can also collect.

How is metal roofing held down?

Exposed Fasteners

The majority of metal roofs currently in use today hold themselves in place by means of mechanical fasteners - usually corrosion-resistant bolts or screws that anchor the roof in the underlying decking material. Fasteners generally fall into one of two categories: exposed or concealed.

What should I put between treated wood and metal?

Isolating the steel from the wood with water resistant barrier materials is an extremely effective way to minimize corrosion issues with the ACQ-D treated wood. Such materials would include ice and water shield, polymer tapes, masking, and lining materials.

Can you put metal roof over rotted roof?

In almost every case, the answer is yes, you can lay down a new metal roof over an existing shingle roof. This is one of the many reasons metal roofs keep growing in popularity – their installation doesn't require completely tearing off the existing roof, which is a time-consuming and expensive job.

Will pressure treated wood react with metal?

When using the new Pressure-treated wood – ACQ and CA, keep in mind that they do have a higher concentration of copper, which results in a chemical reaction that discolours and corrodes aluminum and some metal fasteners.