Metal roofs are great because they last longer than asphalt shingles, they look nice, and they provide protection from the elements. However, metal roof over shingle problems are common. In fact, most homeowners will encounter at least 1 problem with their metal roof before they even get started.
We’ll also cover the top 6 metal roof over shingle issues you might run into during the installation process. And finally, we’ll talk about how to fix each issue once it occurs.
Some Problems That You May Experience with Metal Roofing Installations Over Shingle Roofing
Metal roofing is a great way to protect your home for many years to come. It’s a great investment that can pay off in a lot of ways such as with energy efficiency, better protection during storms, and let’s face it, metal roofing looks great on home. Many home buyers also consider metal roofing to be a better roof even if the price is relatively similar to high quality asphalt shingles.
With that being said however, metal roofing when compared to an asphalt roof can have it’s problems. The biggest problem many people complain about is the noise when it rains. While this can be a concern, many builders will suggest adding the metal roof over your existing roof which is known in the roofing industry as a re-roof. This solution can solve the noise problem for the most part. However, a metal roof installation does come with it’s own set of problems.
Understanding the Re-Roof Process or Roof Over Existing Roof
If your previous roof is showing signs of wear and tear, or if it’s simply time for a change, you may be considering a roof over or re-roof as a roof replacement method. This involves installing new shingles or metal roofing over your existing shingle roof. It’s important to understand the roof over process before making any decisions, as there are a few things to keep in mind which can impact how the roof performs long term.
The first thing to consider is whether your roof can handle an additional layer of roofing and if there is any structural damage that you should repair first. If it’s in good condition and a lighter metal roofing is used, then a roof over should be no problem. However, if your roof is already weakened or damaged, then an additional layer could cause serious problems. Some jurisdictions also only allow a single layer of roofing to be installed as well.
Another thing to keep in mind is the type of metal roofing you’ll be using and underlayment components that should be installed. Using lighter metals and smaller furring strips can help combat some of the weight issues.
Finally, you’ll need to take into account the cost of materials and labor. A roof over will typically cost less than a completely new roof, but it’s still not a cheap project. Make sure you get estimates from several different contractors before making any decisions.
If you’re considering a roof over, then it’s important to understand all of your options and choose the best option for your roof. With a little research, you can be sure that your roof will be in good hands. The biggest factor is weight. Although the roof may seem to support the weight initially it may begin to sag later.
There May Be Problems with the Roof Decking Itself
Roof decks are usually made out of wood, and they’re prone to rot, insect damage, and other problems. When getting a new roof installed on your home the old shingles are typically removed which exposes the roof decking. This allows any problems to be observed and repaired prior to the new roof going on. The problems don’t show up when you’re installing metal roofing over the existing shingles since the shingles are not removed. The roof decking is not exposed and can’t be inspected from the exterior.
It’s a good idea to inspect the bottom side of the roof from the attic. Be sure to check areas around roof components such as fans or skylights. While this is not the perfect solution to inspect the roof decking it does provide peace of mind knowing that the problems may only be on the exterior of the roof decking.
The Roof May Sag Because of the Additional Weight Added by the Roofing
Additional weight on your roof may cause the roof to sag. This is especially true if there is an overhang or if the shingles are not properly distributed. If you have roofing installed, make sure that the contractor takes this into account when installing the roofing. Otherwise, you may end up with a roof that sags and is unsightly.
Metal roofing comes in many different sizes, shapes, and colors. Typically higher quality metal roofing planks are thicker. Sometimes being twice as thick as lower quality metal roofing. Paint also adds weight to the planks. Another components of the metal roofing is furring strips. All of these items can add weight to the roof. If your roof already has architectural shingles installed which are quite heavy then adding the additional weight of a metal roof may be too much. The roof may start to sag in areas which can be unsafe and unsightly.
Some Roofing Components Are Not Replaced or Inspected
If you’re planning on replacing your roof, it might be tempting to skip over the step where you tear off your current roof. But doing so could mean big problems down the road. You simply don’t know what’s going on under the existing roof. And if your roof already has problems now, you’re not fixing them, you’re just covering them up.
Metal roofs require a specific under-layment. While most roofers recommend using asphalt shingles for metal roofs, there are some instances where you’ll need to use something else. For example, if you live in an area prone to heavy snowfall, you’ll need to use a different underlayment than if you live in a milder climate. In addition, metal roofs aren’t typically installed on homes built before 2000. So if you plan to do so, you’ll need to ensure that your house has been retrofitted properly.
Tear off your existing roof. Before you even think about putting a new roof on your home, you’ll need to remove the old one. Doing so gives you a chance to inspect the integrity of the roof and identify potential issues. Plus, it allows you to take advantage of any warranty coverage that’s still active. Once you’ve removed the old roof, you can start thinking about how you’d like to cover it.
Finding Roof Leaks Later Can Be a Problem
When you install a metal roof over an asphalt shingle roof there is typically a gap between the two roofing materials. If the existing roof is not level and flat the furring strips might also be used to ensure the metal roofing lays flat and looks good after the project is done.
The problem occurs because in this space between the two roofing materials, water can travel down the old roof or down the furring strips to other areas of the home’s roof. The roof leak may initially show up on the metal roof near the top of the home only for the water to travel down further away before it finds a way in from the shingle roofing.
Keep in mind too that when the metal roof is installed over the shingle roofing it will damage the shingles underneath. So it’s not like you have two layers of protection. The shingles have punctures from where the metal roofing was installed and if the shingles were older then they also likely cracked during the installation process which can make a lot of ways for water to get in the home from the area between the roofing.
Covering Up the Problem Doesn’t Make It Go Away
Metal roofs are often touted as a solution to many roofing issues. But they aren’t magic bullets. Metal roofs won’t fix everything about your old shingle roofs, and they may actually make some problems worse. And if your roofing already has a problem such as sagging it’s almost a guarantee that it will get worse.
Covering up an old roof doesn’t do anything to help the underlying problems, like leaks, rot, and mold. And while it might look good, it could cause even more damage down the road. So make sure that whatever type of roofing you install that it’s done by removing the old roof to find and repair any problems with the roof so you’ll be protected for many years to come.
Condensation Building on Metal Roofing
Condensation on metal roofs is usually caused by water evaporating off the wood and dripping onto the surface of the roof. If you live in a humid climate, it could take several months for the problem to show up. You might see white spots where the water drips. Or you might notice some discoloration around the edges of the shingles.
There are many different types of metal roofs. Some are designed specifically to shed rainwater while others do not. But regardless of what type of metal roof you have, there is an easy way to stop condensation. It starts with proper underlayment for the metal roofing. Some roofers won’t install any type of underlayment when installing metal roofing over shingles.
What benefits should I expect with metal roofing over shingles?
There are several benefits to roofing over shingles: extended roof life, reduced energy costs, improved aesthetics, and increased property value. By roofing over your existing shingles, you can extend the life of your roof by 10-15 years. In addition, metal roofing reflects heat away from your home, resulting in lower energy bills during the summer months. Metal roofing also provides a clean, sleek look that can increase the curb appeal of your home and boost its resale value.
How do I know if my roof is suitable for roofing over?
In order to be eligible for roofing over, your roof must be in good condition with no more than two layers of shingles. If your roof has more than two layers or is in poor condition, you will need to strip your roof down to the bare roof deck before installing a new roof.
What underlayment requirements should be used with a metal roof over shingles?
If you plan on installing any type of metal roofing be sure to check with the manufacturers requirements. They will typically list the approved types of underlayment needed. The roofing underlayment provides a water-resistant barrier between the roof deck and the metal roofing.
Can you add more than two layers of roofing on a home?
In many cases, you should not install metal roofing over two layers of a roofing material such as shingles simply because of the weight issue. Local building codes may limit the number of roofing layers permitted on a roof, so it’s always best to check with your local building department before proceeding. If you are roofing over asphalt shingles, we recommend installing a layer of roofing felt over the existing shingles to help prevent leaks.
While each problem listed above is unique, they all share one common cause: poor installation done by the roofing company. So, if you want to avoid having any of these issues, you’ll need to hire a professional roofing contractor who knows exactly what they are doing and has experience installing metal roofing over existing asphalt shingle roofing.