Thursday, November 17, 2022
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Do I Need Underlayment For Metal Roof Over Shingles

Can You Lay Metal Roof Over Shingles

Considerations When Installing Standing Seam Metal Over Shingles

As a general rule, installing one type of roof over another type isnt recommended, but just like everything else in life, there are exceptions to this rule.

Unless you have too many layers of shingles on your roof, you can go ahead and install a metal roof on top of those shingles.

Why is this the case? When you install one roof on top of another, you might not notice any damages that are located on your old roof, and this can cause problems in the future.

The reason why is simple: unnoticed problems will likely only get worse over time, and if you have a brand-new roof on top of one that has problems, things can get complicated.

Indeed, by the time the problems come to a head, so to speak, it will be much more difficult to repair the old roof because youll likely have to remove the new roof first before anything else is done.

The more layers of shingles you have, the more likely youll have problems once you place the metal roof on top of those shingles.

Still, it can be done if there are only a few layers of shingles in the first place.

Some of the damages you can miss include everything from water spots to mold and mildew and maybe even rot, and when you remove the shingles or old roof first, you can take the time to inspect and notice these things so that they can be repaired first.

Nevertheless, if you do decide to install a metal roof over a few layers of shingles, there are some things you need to keep in mind first.

Should You Remove Old Shingles Before Installing A Metal Roof

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. If trapped between the metal roofing and old roofing, moisture can build up and cause mold and rot.

What Is Metal Roofing Installation

A metal roofing installation is essentially when metal roofing panels are installed on a roof, either in a commercial or residential roofing application. Metal roofing is available in the form of panels or shingles. Either can be utilized and applied by a professional roofing company. The starter row of metal shingles needs to be laid down at the drip edge. It needs to be affixed to the roof with metal roofing nails.

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Inadequacy Of Roofing Felt As A Vapor Barrier For Asphalt Shingles In Hot Humid Climates

A Building Sciences Corporation report lso elaborates the usefulness of placing a vapor barrier on the roof deck below shingles in hot humid climates. BSC points out that:

Unvented roofs with asphalt shingles in hot humid climates require a vaporbarrier between the asphalt shingles and the roof deck. This is because asphalt roofing materials store water from dew or rain.

Thus asphalt shingles form a water reservoir not unlike wood shingle or shake roofs.

The report argues that this stored moisture is driven inwards when sun strikes the damp or wet roof surface, and it continues to argue that moisture is driven through vapor-permeable roofing paper, felt, and plywood or OSB roof decking, thus ultimately into the attic space

But unlike an asphalt shingle roof nailed directly to a roof deck, a wood shingle or shake roof that has been installed using best practices includes a disposal path for water absorbed in the roof surface: an air space between the wood roofing and the roof deck, or the installation of wood roofing over spaced nailers or “skip sheathing”.

In cool or temperate climates this does not present a problem because the combination of heavy wetting from due or rain i snot combined with solar heating at high outdoor temperatures, say the authors who go on to argue that that buckled roof shingles observed in the morning relax during the day.

But on an un-vented roof moisture driven inwards in hot humid climates, needs to be addressed.


Taking Care Of Your Building Envelope

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The roof is an important element of the Building Envelope. A Building Envelope is the physical separator between the conditioned and unconditioned environment of a building including the resistance to air, water, heat, light, and noise transfer. It needs to be addressed with the utmost care and consideration. Be sure that the contractor you choose is trained in the best methods of installation. Having the Right Stuff and not having the skill to do the installation nullifies the benefits of its use.

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Position And Fix Venting

Once your metal panels are in place its time to cut any holes for your roofing venting, chimney or other outlets. Use a jigsaw with a metal cutting blade they have lots of small teeth. You can also use power shears or tin snips, but youll need to then use a different saw to cut through the roof sheathing.

When you install your vents or chimney be sure to use lots of silicone above and below the opening.

How Do You Attach Insulation To A Metal Roof

Install rigid foam insulation over the entire surface of the roof. Place the sheets close together but dont let them overlap. Use duct tape to seal the seams and further protect against moisture/air leaks. According to the manufacturers instructions, install the metal roofing panels over the insulation.

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Some Specific Benefits Of Metal Roofing

A modern metal roof is engineered to be durable and long-lasting, but there are several other aspects of metal roofing that also worth noting. Here are just a few:

  • Can easily last 75 years or longer with proper coatings and careful installation.
  • Designed to withstand strong wind gusts, flying debris, hail, and snow accumulation better than other roofing materials.
  • Metal is a class A fire-rated roof covering, and metal is also much better at deflecting & diffusing the impact of lightning strikes.
  • Metal roofs dont crack, warp or peel over time, unlike asphalt-based or wood-based roofing.
  • Metal roofing helps to decrease the ambient roof temperature as compared to an asphalt roof this can help to extend the service life of your roof, attic, and connected infrastructure.
  • Metal roofs contribute towards a more energy-efficient structure thanks to their ability to reflect more solar radiation and absorb less heat. One positive result is lesser cooling needs during the warmer months, which means youll save both energy and

What Should Go Under My Metal Roofing

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When aluminum roofing came on the scene, it was found that it, too, could be installed over battens. This was because of its high strength / low weight ratio. Installation over battens was cheaper than putting down dimensional lumber to create a smooth surface. Also, on steep roof surfaces, the battens provided a ladder of sorts for roof access. This was in the days before various scaffolding and other equipment was commonly available.

The other option for installing metal roofing calls for a solid deck to be in place and then the roofing is attached to it. A solid deck originally meant dimensional lumber installed tightly together. Today, it often means plywood or oriented-strand board .

Standing Seam Metal Roof installed on solid decking.

As metal roofing systems were developed in this country, starting originally with hand-formed panels and then machine-fabricated corrugated sheets, the focus was on systems which could be installed over battens.

Over the years, a problem has developed with metal roofing installed over battens. That problem is the accumulation of condensation on the back side of the roofing panels. If this condensation accumulates too much, it quickly causes a dangerous situation for toxic mold and other problems in the attic space.

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Installing A Metal Roof On Wooden Planks

In climates with frequently changing temperatures, moisture can form between the layers of the roof. And how to install metal roofing over shingles to prevent condensation? To do this, you need to create an air cushion between the two layers of the roof.

This air cushion is created when wooden planks are used before installing a new metal roof. These quarter-inch wooden planks are installed directly on the asphalt roof, and a metal roof is already attached to them.

This installation method is very common because it avoids several problems at once. First, you reduce the chance of dents and bends in the metal roof. Secondly, the correct installation of the planks allows you to create an open-air space between the two roofs and will not allow moisture to accumulate.

For such a roof to function correctly, the wooden planks must be installed parallel to each other. If some of them are vertical, and the other part is horizontal, then in some places closed air pockets will form. This will disrupt the natural circulation of air and condensation will form.

Do I Need Underlayment For Metal Roof Over Shingles

Yes, you do need underlayment. The underlayment adds additional protection against moisture buildup in your roof. Steel rots too. Yes, your asphalt shingle roof acts as underlayment. But moisture buildup between the two deteriorates both materials.

What underlayment can you use?

You may think your old asphalt shingles provide the best roof underlayment for metal roof installation. Some experts may even suggest that it is suitable. I beg to differ.

Prevention is better than cure. Add some underlayment before putting metal roofing over your existing asphalt. Rubberized asphalt is a good option.

If you do not add this layer of underlayment, you may lose the warranty on your metal roof materials.

If you want to be more thorough, add purlins to create space between your old and new roof. Purlins provide ventilation while keeping the metal from resting on the shingles beneath.

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How To Install Metal Roofing Over Shingles Or An Existing Metal Roof

Installing metal roofing over existing shingles is an excellent way for contractors to help building owners not only maximize the longevity of their new roof but also to save on roof tear off expenses. There are billions of square feet of roofing on commercial and industrial buildings in the United States. Much of it in need of roofing repair as most contractors know and see every day.

Can You Put Metal Roofing Over Wet Tar Paper

Can a Metal Roof be Installed Over Shingles?

Do not shingle over wet or damp roof sheathing or damp felt paper. The trapped moisture cannot evaporate when the sun heats the shingle. Use metal flashings where the shingles butt up to a wall, chimney or skylight. Do not use caulking, roof tar or asphalt mixes to cover flashing materials.

Does plywood go under a metal roof?

For many applications, a layer of plywood underneath your metal roofing is an unnecessary expense. Boards measuring 1 inches by 4 inches or 2 inches by 4 inches are commonly used for purlins, though never use treated lumber because it will corrode the steel roof and fasteners.

Can you put metal roofing directly over shingles?

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 doesnt require completely tearing off the existing roof, which is a time-consuming and expensive job.

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Is It Possible To Install Metal Roofing Over A Shingle Roof

Yes, you can install a metal roof over existing asphalt shingles. As long as you meet all the requirements of your local building department, the shingles do not necessarily have to be removed before installing metal roofing.

That’s the short answer to the question: can you install metal roofing over a shingle roof? However, just because you can doesn’t mean that you should. Before deciding to go this route, there are several important factors to consider. You probably have questions about the installation process, as well as the pros and cons of not removing your existing shingle roof. All of that and more will be answered in this article. Lets begin.

Get Help From The Pros

If you are interested in installing a new metal roof on your home, we at Roof Crafter Inc would love to help. Our has the experience and knowledge to answer your questions and give you the right tips and information to safely and securely install your metal roofing.

Roof Crafter Inc is a fully licensed, bonded, and insured general contractor. Family-owned and -operated, we specialize in storm damage repair, restoration, and roofing replacement. For more information about metal roofing installation, or any other questions about your homeâs roof repair and restoration needs, contact Roof Crafter Inc at 982-5252 to schedule a free inspection.

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Exceptions To Putting Roofs Over Shingles

Of course, you cant always put other types of roofing over existing shingles, whether theyre metal or not. If the shingles have been covered over multiple times, the layers may have become too thick and will need to be removed before you can put another roof on it safely. You may also need to repair the roof if it has been damaged.

Putting a roof over shingles can only be an issue if the roof material is heavy enough to cause structural damage. Because metal is quite light, this is only likely to happen if there are many layers of asphalt shingles.

Keep in mind that were talking about putting metal over asphalt shingles. Wood shingles may be too thick to have metal roofs placed over them, as the wood shingles could deform the sheets. If the asphalt shingles arent even, this could also create other issues. If youre unsure, the best thing to do is contact a professional. Theyll take a look at your existing roof and the material you want to put over it and determine whether its the best option.

Determining If A Roof

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You should have your roof inspected by a professional roofer to check for the following:

  • Leaks or issues that need to be resolved
  • Wood under the shingles is not rotted
  • The condition of the shingles
  • How many layers of roofing are already on your home

In addition to checking the condition on the current roof, you, or your roofer, should confirm with the county that more than one layer of roofing is permittable.

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What Is The Best Way To Install A Metal Roof Over Shingles

If you wish to install metal roofing over shingles, its recommended to do it one of two ways. The first is to apply an approved underlayment over the old shingles. This is the fastest way to install but it doesnt provide the flattest surface for metal roofing installation. The second way is to install 1×4 purlins over the shingles. This is more expensive but will also be higher quality.

Laying Down Metal Panels

Overlap the panel by half of an inch over the edging. Do not over-tighten the screws. You will know if you screwed them in too tight. The water-resistant gasket should not squish out under the head of the screw. If you see the water-resistant gasket, your screws are too tight.After laying the first panel, continue by overlapping each panel. Where each panel overlaps, use a silicone sealant to add an airtight and watertight seal.Repeat this process until you complete the job.

Although you are installing a new roof over an old one, you still need ventilation and flashing. You cannot rely on your old ventilation system. Your new roof covers it.

Flashing and ventilation protect your roof and home from water damage.

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Can You Install Metal Roofing Over A Shingle 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 doesnt require completely tearing off the existing roof, which is a time-consuming and expensive job.

Metal, although super-strong, is very light, weighing less than a pound per square foot compared with as much as four pounds per square foot for asphalt shingles. Adding a metal roof over existing shingles doesnt significantly increase the overall load for the home structure to bear.

Along with saving the cost of completely removing the existing roof, installing a new metal roof over a current roof also brings the benefit of additional insulation above your home to prevent heat and cool from escaping.

And since we mentioned insulation, we should also mention that metal roofs are heat-blockers they reflect heat away from their surfaces rather than absorb it. This means the extra insulation from your shingle roof will not act as a heat trap for heat emanating through your metal roof.

Flashings To Enhance And Protect Your Steel Roofing

How to Install a Metal Shingles Roof

Weatherproofing is a vital part of keeping your roof sheets and the inside of the building in good condition. A ridge flashing covers where two metal roofing sheets meet at the roofs apex, while barge boards can be used to weatherproof and neatly finish the edges of steel roof sheets.

Many flashings are available to suit our full range of metal roofing sheets for more information please head to the flashings section. Flashings enhance aesthetics, helps protect roof sheets against potential water intrusion and are an integral part of any steel roofing project.

Be sure to check through our Frequently Asked Questions for an overview of the most common queries we receive at Cladco Profiles about our metal roofing sheets . For everything else, either email or call us on 01837 659 901 we look forward to helping in any way we can.

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