Can a New Roof Be Installed on Top of My Old Roof?

It Depends on Your Home's Unique Situation

If you know it's time for a new shingle or tile roof installation on your house, you might have thought whether you can place the best roof shingles on top of the old ones.

The answer is yes. Now that we've addressed the main topic, let's look at some of the reasons you might wish to do so. Then we'll go through some additional reasons why you shouldn't do it. 

But, before we begin, one point must be made clear: only asphalt shingles can be used to replace old roofs (a process known as "re-roofing"). That's also known as composition shingles. You can't use slate or wood for this process, and you shouldn't mix materials like cedar shakes and asphalt shingles. Also, the original roofing must be in relatively good condition. Otherwise, you're wasting your money.

Benefits Of Placing New Best Roof Shingles on Top of the Old Roof

Let's begin with the benefits of a roof installation on top of the old house roof. Many people decide to place a new roof over their existing shingles because of the following reasons: 

  • Less expensive and less hassle

You can save your money because you wouldn't have to pay the landfill cost of removing the old house roof. Also, there would be no requirement for extra felt paper over the old roof. Roof installation from scratch can take more time than installing a new roof on top of old best roof shingles. 

  • It has a similar appearance and is equally long-lasting compared to roofing from scratch

Installing new shingles on top of the old ones can be as long-lasting as a complete re-roof. It also looks as flawless as re-roofing if it's done under the right conditions, the right way. 

  • The manufacturer's warranty is the same

As long as a qualified installer installs the house roof, the manufacturer will guarantee it for the same period of time as a re-roof.

  • Can provide additional storm protection

If your original roof is in good shape, the extra layer can provide further protection in the event that a top shingle is blown off during a storm.

As you can see, there are numerous advantages to roofing over your old one, and we perform many of these for homeowners. However, there are situations when that is not the proper course of action.

When Is It Better to Tear Off the Old Roof?

As previously stated, the disadvantages of re-roofing tend to exceed the benefits, but it all depends on your specific situation. The following list includes some general reasons not to re-roof, as well as some considerations or items to look into if you're thinking of replacing your roof shingles.

  • Two layers of shingles are already present over your roof

Most building rules only allow for two layers of any roofing on a residence. So, if you already have two layers, the decision is already made for you. You must remove the old roof and replace it with a new one.

  • The current shingles are in bad condition and they're curling

Shingles are suited for flat surfaces. They don't perform a great job bridging the humps, gaps or dips, including overlapping shingles' stepped texture. 

Re-roofers use methods to place new roof shingles over old ones to keep the same step-ups between courses, but if any of the old shingles are curled, cupped or otherwise deformed, those flaws will spread to the new layer. 

For re-roofs, many roofers use dimensional or laminated shingles since they're thicker than ordinary shingles and generally feature a staggered edge profile (for aesthetics) that hides any dips or high places in the existing roofing.

  • Leaking roof during rain and you can't replace the underlayment

If your roof leaks, it's usually best to remove the old roof so you can figure out what's causing the problem and replace it. A leaky roof will not be fixed by putting a new roof on top of it. When you install a new roof over an old one, you can't replace the underlayment. 

Water can get around shingles no matter how many layers of roofing you have. Therefore the building paper (tarpaper) spread between the shingles and the roof sheathing is there for a reason. The underlayment will not safeguard the roof deck against water that gets anywhere near the shingles if old and degraded. 

To prevent ice dams in snowy locations, most new roofs now have an ice-and-water shield (a rubbery moisture barrier) placed to the sheathing along the eave. A re-roof does not allow for the addition of this membrane, and the extra layer of shingles provides little protection against ice dams.

  • Your roof feels spongy and soft

If the majority of your roof feels spongy and soft when you walk on it, you may have an issue with the roof's underlying sheathing. It will be necessary to remove the present roof to repair it.

  • Your roof cannot handle the weight

Composite shingles of excellent quality can weigh between 350 and 450 pounds per square foot. Your roof structure was most likely built to support a deadweight of one sheet of shingles, plus snow and even a safety buffer. 

Installing the new roof shingles on top of old shingles virtually increases the weight of the roofing. So, ensure your roof structure can withstand the additional pressure. That's also why most building rules limit re-roofing to two layers or less. The weight of many layers enables the roof sheathing to sag between the trusses or rafters on some structures.

  • You have plans to move in the future

If you want to sell your home soon, re-roofing may reduce its value and make it tougher to sell. The re-roofing will not affect current homes, but new owners will be obliged to remove two layers of shingles later.

As a result, many home inspectors will flag two-layer roofs and warn potential purchasers about the issues that re-roofing can cause.

If you're still unsure whether to re-roof or replace your roof, talk to a roofing contractor about which option is best for your property.

Request a FREE Professional Opinion on Re-Roofing

You don't have to guess whether you should remove your old roof or replace it with new shingles. True Quality Roofing provides free roof inspections, during which we will carefully assess the state of your roof and walk you through your alternatives.

Get in Touch With Our Team Today!

For more information, contact us today to speak with a True Quality Roofing team member.