Calgary Roofing Done Right Calgary Roofing Done Right

Roofing Underlayment

Roofing Underlayment Options

Roofing underlayment helps prevent water from infiltrating under your shingles and causing damage to your roof structure or the inside of your home.  It also provides an extra layer of protection between your shingles and your roof deck in the case of wind damage or missing shingles.

There are three basic types of underlayment used on sloped roofing:

  • Felt paper
  • Rubberized asphalt (Ice and water shield)
  • Synthetic

Felt Paper

The most common type of underlayment used in residential applications is black felt paper.  Felt underlayment is made from either organic or fiberglass substrate.  This material comes in 2 thicknesses, 15 and 30 pound.  30 pound is thicker and will protect the roof longer than 15 pound if it should somehow become exposed to weather.

Rubberized Asphalt (Ice and water shield)

Rubberized asphalt underlay has an adhesive on the back making it self-adhering. The rubber-like qualities of this underlayment make it seal well around nails, roof edges and penetrations etc.

When an ice & water shield is used, every nail on your roof becomes self-sealed and water tight.

Synthetic Underlays

Synthetic underlays are made from polypropylene or polyethylene. The advantages include their low weight and high strength and non-skid surface.  Synthetics are resistant to fungal growth and are wrinkle-free, since they don’t absorb moisture, they are considered moisture barriers.  They are also very resistant to UV damage and can be left exposed to weather for periods from six months to a year.

All 3 products have distinct advantages and disadvantages and their use in any given application depends on a number of factors.