A Few Good Pointers for Installing Self-Adhered Roofing Underlayments

A Few Good Pointers for Installing Self-Adhered Roofing Underlayments

Self-adhering or "self-stick" roofing underlayments have been around for more than 30 years protecting steep slope roofing applications from moisture damage caused by wind-driven rain, ice dams or failure of the finished roofing surface.

A number of insurance companies and code bodies have begun requiring contractors to cover the entire roof with a self-adhering underlayment to protect the home's interior from this unnecessary water damage. It's no wonder that today, there are more self-adhered products available than single-ply and built-up membranes combined.

Although self-adhered underlayments are easy to install, there are several Installation Keys that should be followed closely to provide maximum adhesion to the roofing substrate:

  • Check First - know all applicable building codes, as well as the manufacturer's recommended installation instructions, prior to the installation of any roofing underlayment. There are often minimum installation temperatures, roof pitch restrictions and exposure ratings on self-adhered underlayments.
  • Adhesion is the Key - ensure that the roofing substrate is clean, dry, and free of waxes, dirt or debris. Just like Scotch Tape, dust and dirt will impair the adhesive properties of the self-adhered membrane.
  • Flash First - always flash around roof penetrations before applying the underlayment in the field of the roof. You can often use the underlayment itself as a flashing material or one of several MFM products.
  • Start Low - always start at the eave and work up towards the ridge to ensure that water will flow over all side laps, which are normally 3" on most self-adhered products.
  • Eliminate Gaps - do not use the underlayment to bridge gaps in the roofing substrate. Always use a flashing material such as MFM Roof Deck Tape or similar, then lay the underlayment on the roof surface.
  • Apply Pressure - applying sufficient pressure with a large 80 lb push or hand roller over the entire surface, paying special attention to any overlap areas.

If you have any tips that you'd like to share, we would love to hear them. If you have any questions, please contact MFM Technical Services at 800-882-7663.