When you need to replace your roof shingles, you might be wondering if the underlayment will need to be replaced as well. You can’t see the underlayment until the shingles are removed, so most roofing contractors will provide a cost for both underlayment and decking replacement just to be safe. It is generally recommended that the underlayment be removed and replaced during the process of roof repair. Let’s explore why that is.
What is Roof Underlayment?
Roofing underlayment is the protective layer that is attached to the roof deck. The shingles sit over the underlayment. This layer is often felt or a synthetic material. It provides a secondary layer of protection from moisture, snow, and wind.
Damaged or Deteriorated Underlayment
Chances are pretty good that if the existing shingles are exhibiting wear and are due for replacement, the underlayment is also damaged or deteriorated to some extent. This is more common than not, especially if you are experiencing noticeable leaks within your home. Additionally, the underlayment may experience some damage while the shingles are being removed.
Building Codes
Depending on your location, regional building codes might dictate whether or not the underlayment is to be replaced to meet the latest code requirements. This is common with older homes that might have outdated underlayment materials or no underlayment at all.
Warranty Requirements
The roofing manufacturer’s warranty for roof repair or replacement, due to roof failure, will often require that the entire roof system be replaced. This includes underlayment, an ice shield at eaves, and flashings. Not replacing these protective layers could void the warranty. It is important to speak with your contractor about the product and workmanship warranties before signing a contract for roof repairs.
Roof Replacement vs. Reroofing
Full roof replacement means you are getting an entirely new roof system, including underlayment and shingles. It could also include complete roof deck replacement. The roof deck is the layer of plywood or wood slats that sit directly atop the roof rafters.
Reroofing involves adding a layer of shingles directly over the existing roof. This is allowable in some areas, depending on how many layers of shingles are permitted based on building code load calculations. This is especially critical in locations that experience heavy snow loads in winter.
Conclusion
The underlayment is the layer of roofing that provides extra protection for the roof deck beneath the shingles. Just like the shingles, the underlayment can deteriorate over time. An aging roof underlayment does not offer the superior protective barrier that a replaced one can. Not replacing the underlayment could lead to leaks and other problems down the road. Always discuss the cost and warranty requirements of underlayment replacement with your roofing contractor prior to beginning the job.
