Fiberglass shingles are a popular roofing choice because they’re lightweight, durable, and resistant to fire. Underlayment is a critical part of the roofing system beneath these shingles. Typically, manufacturers recommend applying a waterproof or water-resistant underlayment to protect the roof deck from moisture, especially during heavy rain or ice dams. This underlayment acts as a secondary barrier if the shingles get damaged or water manages to seep underneath. Common materials include synthetic underlayment or asphalt-saturated felt, with synthetic often preferred for its durability and lighter weight. The exact requirement depends on local building codes, climate, and the specific shingle manufacturer's guidelines. For example, in areas with frequent wind-driven rain or snow, synthetic underlayment rated for water resistance might be mandatory. Missing or poor-quality underlayment can lead to premature roof damage, leaks, and concerns with warranty coverage, as many manufacturers require proper underlayment for their warranties to remain valid.
A simple DIY way to check underlayment is to look for any exposed areas where shingles may be missing or damaged and see if the surface underneath looks intact and free of moisture stains. However, you won’t typically be able to inspect underlayment without removing shingles, so if your roof has any signs of leaks, curling shingles, or water stains inside your home, it’s best to call a professional. When hiring a roofer, ask specifically what type of underlayment they’ll use and if it meets your shingle manufacturer’s warranty requirements. Also, inquire whether they will install it according to code and manufacturer guidelines, including proper overlap and fastening. This ensures the roof’s durability and maintains warranty validity, saving you potential headaches down the line.