Protecting Your Investment

It’s no exaggeration to say that the roofing system is one of the most critical components of a structure. There are a lot of varieties of roofing materials based on maintenance requirements, roof pitch, cost, location, and aesthetics.Options for Roofing Underlayment

An important element in any roof is the underlayment. This refers to the water-resistant layer of protection between the decking (usually OSB) and the final layer of materials used, such as shingles or metal roofing.

The underlayment is there to help prevent age and Mother Nature from causing leaks and water damage. There are a number of different options for underlayment. Here are the three main categories of underlayment:

  1. Black Asphalt-saturated felt
  2. Mechanically attached synthetic underlayment
  3. Self-adhered underlayment

This post goes into a deeper explanation of options for roofing underlayment:

Black Asphalt-saturated Felt

Historically, Roofing felt has traditionally been one of the most common types of underlayment used for residential, steep slope and other applications. It is produced by impregnating paper or in incorporating fiberglass mat with asphalt. This produces a semi water resistant material or membrane that is commonly used in roof construction.  The term “Felt” comes from the historical method of making the base material. Felt is made from recycled paper in large rolls supplied in different thickness in common widths.

Roof Construction

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Self-Adhered Synthetic Roofing Underlayment normally consists of a polyolefin facer combined with a bitumen or butyl combination thereof, a pressure sensitive adhesive, plus a release liner on the very bottom (liner is removed during installation). The adhesive is designed to provide adhesion to the roof deck as well as a waterproof seal around fasteners during the initial installation. During the roofing initial installation, the main purpose for this product category is to provide roofing structures with an enhanced secondary layer of protection for primary roofing materials.

Mechanically Attached Synthetic Roofing Underlayment

Synthetic underlayment is commonly made by coating both sides of a strong inner polyolefin woven or nonwoven membrane with varying layers of polyolefin coatings to produce a water-resistant product.  Each layer constitutes a different contributing feature for optimum performance. Roofing contractors continue to convert in large numbers from felt to synthetic underlayments making this one of the fastest growing segments.

Read more here:  Types of Steep Slope Roofing Underlayment

With a flat roof, the same basic underlayment is used but from there on, the process is quite different from a sloped roof. There are 3 essential classes of flat roofing material:

  • Built-Up Roof – Layers of traditional hot tar and gravel
  • Modified Bitumen – Similar to ice-and-water shield, but impregnated with a mineral-based surface
  • Rubber Membrane – EPDM Rubber Membrane is currently one of the most popular materials for flat roofs

This video shows how torch down modified bitumen is applied to a flat roof:


The cost of a roof is a considerable investment. There are many aspects to examine, such as labor costs, the size and pitch of the roof, materials being removed and new materials being installed, to name a few. The underlayment is also part of the estimate to a new roof as well as roof repair because most roofs have to be stripped down to the decking to check for sagging or rotting wood.

The cost for the underlayment material in Denver for a 1,200 square foot roof with a lower slope can run between $700 and $1,000. This cost is usually figured into the total bid, which depends on a lot of factors, but can range anywhere from $1,200 to $30,000 nationally.

There are sites such as HomeAdvisor.com that offer a calculator based on your exact needs. Your best bet is to contact several reputable Denver roof repair or installation contractors to get a quote.

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