Roofs are complex structures with many parts. The appearance of your roof may be important, but its protection from the elements is determined by the quality of the materials and the installation. Each layer of your roof must be installed correctly and placed correctly to prevent water from leaking underneath.

Roof Structure and Layers

The roof structure serves several functions, including providing a barrier against the elements, protecting the house from fires, and offering stability to the roofing system.


Also known as decking, this is the base on which all subsequent layers of the roof are placed. Roof sheathing can be made of plywood or OSB. The boards and sheets are secured to the rafters to form the innermost covering layer. Sheathing provides rigidity to a roof frame and a surface on which nails and other fasteners can be used during shingle installations.


The first layer of waterproofing is placed between the sheathing and the shingles. Underlayment protects the roof against damaging elements such as snow, ice, and rain. Underlayment, also known as membrane, is required to provide the roof with a barrier that will keep it waterproof. For residential applications, underlayment such as felt, tarpaper or another type is needed. Some homes have an extra layer of ice-and-water shield.

Ice & Water Shield

This layer is designed to shield the roof in areas where water tends to collect and causes the most damage. This includes valleys, eaves, and skylights as well as the area around chimneys. Ice and water shield not only protects these water-sensitive zones but also seals around fasteners and nails to prevent water from seeping in.

Roof Covering

These are shingles or other materials such as tile and slate that make up the outermost roof layer. Shingles are the outermost layer of protection against weather and other outdoor elements.


This article was written by a roofing professional at At, we’re determined to be the only one you need to hire for the entire lifespan of your new roof. We take a modern, professional approach to the roofing business in order to ensure our customers in St. Petersburg and the Central Florida region have the best possible experience whenever they choose us.