Roofing Underlayment Explained

Roofing Underlayment

How important is roofing underlayment? It’s critical to any properly installed roofing system. It’s the material that is laid over your entire roof deck surface prior to the main roofing material installation.

Underlayment is the most important waterproofing component of your roof system, which is why it is often referred to as “dry-in”. When underlayment is properly installed by a Denver roofer, your home is then considered dried-in. To dry-in your home is to waterproof it with underlayment it and protect from exterior elements. Similar dry-in material is installed under your siding, commonly known as Tyvek paper.

At the conclusion of your roof replacement, your underlayment will not be visible, as it lays beneath the shingles or tiles. Underlayment is excellent at being waterproof and water resistant, but is not resistant to UV rays. Your shingles, tiles, or metal roof surface that cover the underlayment provide protection from the sun (and moisture).

There are different types and some specialty underlayments to know about.

Types of roofing underlayment are:

  • Felt paper. This was the most common underlayment of decades past, and some Denver roofing companies still use it to save money. Felt paper is made by creating a thin layer of felt material, and saturating it in asphalt to give it a waterproofing ability. It comes in 15 lb (thinner) or 30 lb (thicker) variations.
  • Synthetic. Synthetic underlayment is thinner, lighter, stronger, and longer lasting than felt paper. That’s why we only use synthetic underlayment at Sol Vista Roofing. Examples of some of our favorites include Owens Corning Rhino Roof, Certainteed Diamonddeck, and Eco Chief Solarhide (especially for DaVinci roofs).
  • High-temperature. High-temp underlayment is used in metal roofing and at high elevations. It has a radiant barrier to protect against the additional heat that is a byproduct of metal roofing. Some of the best known high-temp underlayment for metal roofing is Sharkskin Ultra.
  • Fire rated. In some scenarios, a special underlayment may be needed to achieve a class A fire rating. Synthetic underlayment with asphalt shingles will achieve class A fire rating, but, for example, stone-coated steel roofing above 7,000 feet elevation requires a specialty underlayment, such as GAF Versashield, to be rated as class A.
  • Ice and water shield. Thicker rubberized asphalt based self-adhering membrane. Extra tough waterproofing used in higher-risk areas of your roof such as eaves and valleys. In some mountain roofs, we install Ice and water shield on the entire roof. A couple of our preferred products are Owens Corning WeatherLock, and Grace Ice and Water Shield.
Roof Underlayment
A Sol Vista roof dried-in with Owens Corning Rhino Roof underlayment









Roofing Underlayment Installation

Your Denver roofer will use the underlayment rolls to carefully cover your roof deck from the bottom-up with at least a 3 inch overlap between rows. The underlayment is then attached to the roof deck using plastic-cap nails, which are one-inch nails that have a one-inch plastic headcover for waterproofing the nail hole. While self-adhered underlayments (like ice-and-water shield) don’t require plastic caps because they self-adhere, most Denver roofing company do use a small amount for extra protection. After the entire roof deck is covered with underlayment, the shingle, tile, or metal roof material installation can begin.