What is Cap Sheet Roofing?

In this article from RRG Roofing, we will discuss, what is cap sheet roofing, its components, benefits, types, installation process, and maintenance to understand its performance better.

Components of Cap Sheet Roofing

Cap sheet roofing is a multilayered system comprised of the following:

Base Sheets

Cap sheet roofing is built upon a base sheet, typically made of fiberglass or polyester. The base sheet ensures a secure and long-lasting bond between the other layers.

Interplay Sheets

Typically made from fiberglass or polyester, interplay sheets are layered between a base sheet and a cap sheet. The sheets add structural strength and help distribute weight evenly.


Cap Sheets

It consists of a thick, weather-resistant material such as modified bitumen and fiberglass or polyester with fiberglass reinforcements. Cap sheets provide a final layer of defense against UV radiation, rain, and wind.

Benefits of Cap Sheet Roofing

Cap sheet roofing offers several advantages over traditional roofing materials:


Unlike other roofing materials, cap sheet roofing has a multilayered structure that provides exceptional durability and wear resistance.


Rainy or snowy regions can benefit from the cap sheet because it creates an impermeable barrier.


An additional layer of fire protection is provided by cap sheets treated with fire-resistant materials.

Energy Efficiency

By reflecting solar radiation, cap sheet roofing reduces heat absorption, allowing indoor temperatures to stay cooler, resulting in lower energy bills.

Types of Cap Sheet Roofing

There are two main types of cap sheet roofing:

SBS-Modified Bitumen Cap Sheets

Enhanced thermal shock resistance and excellent weather resistance are provided by SBS (styrene-butadiene-styrene) bitumen cap sheets.

APP-Modified Bitumen Cap Sheets

Modified bitumen cap sheets made of APP (atactic polypropylene) exhibit exceptional heat resistance and can withstand extreme temperature changes. They are also tough and durable.

Cap Sheet Roofing Installation

In order to properly install a cap sheet roofing system, you will need the following tools and materials:

Tools and Materials

Some of the essential tools and materials for roof cap sheet installation include:

  1. Roofing nails
  2. Roofing cement
  3. Primer
  4. Modified bitumen sheets (base, interplay, and cap sheets)
  5. Roofing torch or hot-air welder
  6. Utility knife
  7. Trowel
  8. Broom
  9. Seam roller

Installation Process

In order to properly install cap sheet roofing, you should follow the manufacturer’s instructions and the specific product instructions. However, the general steps include:

Preparing the roof surface: 

You need to remove debris and clean the roof surface thoroughly.

Priming the surface: 

Apply a primer to the roof surface, ensuring proper roofing materials adhesion.

Installing the base sheet: 

Use roofing nails or adhesive to fasten the base sheet to the roof surface 

Installing interplay sheets (if applicable): 

Using a heat welder or adhesive, attach the interplay sheets to the base sheet by overlapping the edges.

Installing the cap sheet: 

Ensure the cap sheet overlaps the edges as instructed and heat welds or adheres it to the interplay sheets or base sheet.

Sealing the edges: 

A trowel or seam roller should be used to apply roofing cement to the edges and press it down to create a watertight seal.

Maintenance and Repair

Routine maintenance is crucial to ensuring cap sheet roofing system longevity and performance. It is essential to conduct regular roof inspections in order to detect potentially costly issues early and prevent extensive damage or premature roof replacement. If damage is detected, a timely repair should be carried out to ensure that the roof is in good working order.


Buildings of all shapes and sizes can benefit from cap sheet roofing, which is durable, weather-resistant, and cost-effective. Choosing a roofing system that meets the needs of the property owner or contractor requires an understanding of the components, benefits, types, installation process, and maintenance requirements.


Q: What is the average lifespan of cap sheet roofing?

Sheet roofing systems will typically last between 20 and 30 years, depending on the quality of the installation, maintenance, and environment.

Q: Is cap sheet roofing suitable for all climates?

Due to their design, cap sheet roofing products are suitable for various climate conditions, including extreme temperature fluctuations, heavy rain, and high winds. However, it is essential to choose the right sort of cap sheet for the specific climate (SBS or APP).

Q: How much does cap sheet roofing cost?

Cap sheet roofing prices vary based on factors such as the quality of the material, labor costs, and the project’s location. Obtaining quotes from multiple contractors helps you get the best deal.

Can cap sheet roofing be installed over an existing roof?

Cap sheet roofing can sometimes be installed over an existing roof, providing the surface is clean, dry, and structurally sound. However, you should consult with a professional before attempting this.

Q: Is cap sheet roofing eco-friendly?

In addition to being recyclable, cap sheet roofing materials can improve energy efficiency, reducing the building’s carbon footprint. Materials sourced, manufacturing processes, and disposal methods influence the environmental impact.

For more information, contact RRG Roofing at 678-326-4951. We service areas in Dahlonega, Blairsville, Hiawassee, and Alpharetta, GA.

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