How to Install Metal Roof Underlayment Over Shingles: 1 Minute to a Weather-Resistant Roof Installation

Installing metal roof underlayment over existing shingles is a practical approach for many homeowners seeking durability and energy efficiency without a complete tear-off. The underlayment acts as a moisture barrier and adds a level of insulation, extending the lifespan of your metal roof. The process requires careful preparation and selection of the right materials to ensure optimal performance. Here’s a concise, step-by-step guide to help you get started:

1. Inspection and Preparation: Begin by inspecting your existing shingle roof. Make sure there are no damaged or loose shingles that could affect the new installation. Remove any debris and secure any protruding nails.
2. Install Furring Strips (Optional): Depending on your local code and design preferences, you may install wood furring strips horizontally across your roof. These provide a ventilating gap beneath the metal and a more level surface for the underlayment.
3. Select the Right Underlayment: Synthetic underlayments are recommended for metal roofs over shingles due to their superior durability and moisture resistance. Self-adhering membrane or high-temp underlayments are even better in areas prone to ice dams.
4. Applying the Underlayment: Start at the lowest edge of the roof, rolling out the underlayment horizontally. Overlap each row by at least 4 inches and make sure vertical seams are staggered. Secure with roofing nails or screws, following manufacturer instructions.
5. Flashing and Details: Ensure all vents, valleys, and edges are properly flashed. This crucial step prevents water intrusion at vulnerable points.
6. Ready for Metal Panels: With underlayment fully secured and all flashing in place, your roof is now ready for the metal roofing panels.

As a designer, I’d recommend considering the sustainability aspects of your choices. Not only does working over old shingles keep material out of landfills, but a correctly installed underlayment increases the energy efficiency of your space. For a streamlined digital approach to visualize and plan these upgrades, many professionals leverage online home designer tools which allow for precise layout and material selection tailored to your exact needs.

Tips 1:

For best results, always check your local building codes. Some areas may require a full tear-off or stipulate specific types of underlayment. Additionally, proper ventilation is critical beneath both the underlayment and the metal roofing to prevent condensation and prolong roof longevity.

FAQ

Q: Can you put metal roofing directly over shingles?

A: Yes, in most cases you can install metal roofing over one layer of existing shingles. However, proper underlayment and local code compliance are essential for long-term performance.

Q: What type of underlayment is best for a metal roof over shingles?

A: Synthetic underlayments or high-temperature ice and water shield membranes are typically recommended for best moisture protection and durability.

Q: Do I need to remove old shingles before installing metal roofing underlayment?

A: Generally, one layer of old shingles doesn’t need to be removed unless they are severely damaged or local codes require it.

Q: How do you attach underlayment over shingles?

A: Underlayment is rolled out horizontally and attached using roofing nails or screws, overlapping each row and ensuring a watertight seal.

Q: How important is flashing when installing a metal roof over shingles?

A: Flashing is crucial to prevent leaks at roof edges, valleys, and around penetrations, ensuring long-term weather protection for your metal roof system.