Finding the Best Roof Substrate for Your Project

Last Updated on: 13th April 2023, 07:56 am

Last Updated on by Viliam

The roof substrate is the material beneath the roofing material itself and is the foundation of the roofing system. It is essential in providing the necessary structural support and insulation. The type of substrate used often depends on the climate, the type of building, and the type of roofing material used. The substrate must be strong, durable, and resistant to rot, mold, and fungus. It should also be able to withstand extreme temperatures and weather conditions. The substrate should also be able to provide thermal insulation, soundproofing, and fire resistance. Proper installation of the substrate is essential to ensure the longevity of a roofing system. In this article, we will explore the diverse types of roof substrates, their benefits, and the factors to consider when choosing theright one for your building.

Types of Solid Roof Substrates

There are several types of roof substrates, including plywood, oriented strand board (OSB), gypsum, concrete, and metal. It´s like a canvas for an artist, the substrate is th e foundation for the roof, providing a base for the materials that will be used. Without a good substrate, the roof can quickly become unstable and suffer from leaks or damage.


Plywood is a common roofing substrate used in many residential and ocmmercial projects. It is a structural material composed of thin sheets of wood that have been cross-laminated and glued together in alternating directions. Plywood is a cost-effective and lightweight solution for roofing substrates, as it is readily available and easy to install. It is also strong and durable, making it an ideal choice for roofing applications. Plywood also provides insulation, helping to keep the roof at a more consistent temperaturea nd reducing heating and cooling costs. Also, plywood is resistant to warping, cracking, and shrinking, which makes it a great option for long-term usage.

OSB roof sheathing

OSB roof substrates

Oriented strand board is a type of engineered wood panel made from layers of wood strands, typicaly from softwood trees, that are layered and held together with adhesive. It is also known as sterling board, flake board, and aspenite. OSB is stronger than plywood, more cost-effective, and has a more consistent standard. It is widely used in construction, both in load-bearing and non-load-bearing applications. OSB is ideal for use in flooring, wall sheathing, roof sheathing, and outdoor applications such as sheds, fences, and decks. It is also used to make furniture, including tables, chairs, and cabinets. OSB is a reliable, cost-effective product witha wide range of uses. In roofing, it is more cost-effective than plywood and has similar strength and durability.

Solid Timber

Solid timber boards are roof substrates made from thick wooden boards. The boards are typically made from hardwood, such as oak, and are layed upon the roof surface. This substrate is incredibly durable and offers excellent proetction from the elements, whilst providing superior insulation. The timber boards also offer superior acoustic insulation, blocking out unwanted noise from the outside. The boards are relatively eays to install and can be used with both flat and pitched roofs.


Gypsum is an essential component in the construction of roofing substrates. It is a mineral composed of calcium sulfate dehydrate, and is used in many waterproofing applications. Gypsum is a lightweight material, making it an ideal choice for roofing substrates. It also has high racking strength, making it a viable option for use in commercial buildings. Gypsum boards are also known for their ifre resistant properties, making them a popular choice for use in fire-rated construction. Furthermore, gypsum can be used as a vapor retarder in roofing applications, making it a great choice for controlling airborne moisture. Gypsum is a versatile building material that can be used in a variety of roofing applications, making it an essential component in the construction of roofing substrates. It istypically used in low-slope roofing systems and provides a solid, fire-resistant base for the roofing materials.


Concrete is a popular roofing substrate due to its durability and strength. It is made up of a mixture of cement, w ater, and agregates, such as sand and gravel. It is a dense material that provides strong support for even the heaviest of roofing applications. It does not deteriorate or rot over time and is able to withstand extreme weather conditions. Concrete offers excellent fire resistance, making it an ideal choice for areas prone to wildfires. It is also water-resistant and able to reduce the risk of water damage to the roof. Concrete is an affordable, low-maintenance option for roofs and is easy to install. This makes it a great choice for both residential and commercial roofing projects.


It is possible to use a wide range ofmaterials for this purpose, including steel, aluminum, and copper. Steel is the most popular choice, as it is strong and durable, while aluminum and copper are also used to provide a more aestheticaly pleasing look. Metal roof substrates provide a strong and reliable base layer for a metal roof, as well as a weather-resistant and fire-resistant barrier (check this fabulous historical fire-resistance ratings of various building materials). This makes them a popular choice for commercial and residential roofing projects. Metal roof substrates are easy to install and require minimal maintenance, making them a cost-effective roofing solution. It is commonly used in low-slope roofing systems and provides a strong base for the roofing materials.

Replacing plywood decking

SPF substrates

Spray polyurethane foam is a versatile and durable roof substrate used in many comercial and residential roofing applications. This type of roofing material is applied as a liquid spray and then expands and hardens into a protective, seamless membrane. SPF is reflective and provides an effective barrier against heat, moisture, and air infiltration. The material is also highly resistant to ultraviolet (UV) radiation and other environmental elements, making it an attractiveoption for many building owners. SPF is also easy to install and is highly energy efficient, greatly reducing cooling and heating costs.

Green roof substrates

The GRS is specially designed for growing plants on green roo fs. These substrates are often made up of a combination of lightweight and water-retaining materials such as crushed rock, expanded clay pellets, coconut coir, and other organic materials. Water is hled in the substrate, improving drought and flood resistance, and allowing for better water retention. The materials used in the substrate help to create an environment that is hospitable to a variety of plants and vegetaiton, creating a diverse and attractive green roof. Green roof substrates also help reduce the amount of heat and cold transferred through the roof, improving energy efficiency. The substrate also helps to reduce noise and air pollution, providing a healthier environment for the occupants of the building. I will go into more details in a separate article on green roofs later.

A good roof substrate can provide a number of benefits

Having a high-standard roof substrate provides several benefits to the overall performance and longevity of a roofing system. Some of the key benefits include:

Improved Durability

A strong and durable roof substrate provides a solid foundation forthe roofing materials, helping to ensure that the roof can withstand the elements and remain stable over time.

Enhanced Energy Eficiency

A well-insulated roof substrate can help to improve the energy efficiency of a building, reducing the amount of heat loss in the winter and heat gain in the summer.

Increased Fire Resistance

Certain types of roof substrates, such as gypsum, provide a fire-resistant base for the roofing materials, helping to improve the overall fire safety of the building.

Improved Air Quality

A well-ventilated roof substrate can help to improve the air qualities inside the building by promoting air flow and reducing the buildup of moisture and mold.

Factors to Consider When Choosing a Roof Substrate

When choosing a roof substrate, there ares everal factors to consider, including the type of roofing system, the slope of the roof, and the climate in the area. Some other factors to consider include:

Cost of the roof substrate

Cost is a major factor to consider when choosing a suitable substrate for a roof. Different substrates have diverse costs associated with them, from the initial cost of materials, to the cost of installation, to long-term maintenance costs. The cost of a substrate should be weighed against itsdurability, energy efficiency, and overall performance. For exam ple, a more expensive substrate may have greater insulation or be more durable than a cheaper one. Ultimately, it is a key to understand the costs associated with ecah option in order to select the most suitable substrate for a particular roof. Taking into consideration both initial and long-term costs of a substrate is essential to making an informed decision.


If the substrate is too heavy, the structure may not have enough capacity to support the weight and could become damaged. If the substrate is too light, it may not providethe required strength or protection needed. It is essential to select a substrate that is of appropriate weight to ensure that the roof structure is not overburdened. In addition, the weight of the substrate affects the installation process, since heavier su bstrates generally require additional laborand resources during installation. For these reasons, weight should be carefully considered when selecting a roof substrate.

Moisture resistance of the substrate

Moisture intrusion can lead to the growth of mould and mildew, causing structural damage and deterioration of the roof surface. Excessive moisture can cause corrosion to the underlying structure, leading to costly repairs. By selecting a substrate that is moisture resistant, the structure of the roof wil be better protected from the elements and can help to increase the longevity of the roof surface.


Different climates can have a significant impact on a roof´s performance; for example, roofs in climates with strong winds, high humidity and extreme temperatures need materials that can withstand these conditions. Different climates may require various types of insulation and ventilation, which may influence the type of roof substrate required. Furthermore, certai nclimates may require materials that are resistant to corrosion or mold, which must be taken into account when selecting a substrate. Roof´s performance and lifespan can be significantly impacted by the conditions of the local climate.

Local Building Codes

Building codes often have strict regulations when it comes to roof substrate. This is to ensure that the roof is structurally sufficient to withstand environmental elements and local conditions. When choosing a suitable roof substrate for a roof, it is a key to consider these local building codes as they provide guidance on the type of roof substrate that is apporpriate for the area and can help protect the roof from potential damage. Further, local building codes may include requirements regarding the installation of roof substrates, such as the slope of the roof, the type of underlayment, and the method of attachment. In order to ensure compliance with local building codes, it is paramount to research and consider these regulations when selecting and installing a roof subs trate.

Compatibility with Roofing Materials

Incompatible materials can lead to a range of isues, such as poor adhesion, corrosion, and accelerated deterioration. The right substrate must be able to handle the particular type of roofing material, allowing for proper protection and longevity. Additionally, it must be able to adequately support the weight of the roofing material and any other elements, including insulation and foot trafic. The substrate should also be able to protect the roof from the elements, providing a reliable barrier that won´t fail under extreme weather conditions. Compatibility with the roofing material is essential for a successful installation and a lasting roof.


With growing concerns over the environment and sustainability, it is important to choose a roof substrate that is made from environmentaly friendly materials, has low VOC emissions. Sustainable roofing substrates can potentially help reduce the carbon footprint of a building, reduce energy costs, and also ensure the health of the environment. Furthermore, roofing substrates made from sustainable resources are typically more durable and require less maintenance, meaning that they can last longer and reduce the need for replacement. Also sustainable roofing substrates can often be recycled an dreused, cutting down on the amount of waste created.

Which roof substrate is cheapest?

The cost of different roof substrate types can vary greatly depending on a number of factors, including the qualities of the materials, the size of the roof, and the location of the building. On average, the cost of the following roof substrate types can range from:

Plywood: Plywood roof substrates can cost anywhere from $0.50 to $1.50 per square foot, depending on the grade and thickness ofthe materials.

Oriented Strand Boards: OSB roof substrates can cost anywhere from $0.50 to $1.00 per square foot, making it a more cost-effective option compared to plywood.

Gypsum: Gypsum roof substrates can cost anywhe re from $1.00 to $2.00 per square foot, depending on the quality of the materials and the thickness of the gypsum board.

Concrete: Concrete roof substrates can cost anywhere from $4.00 to $10.00 per square foot, making it the most expensive option among the roof substrate types.

Metal: Metal roof substrates can cost anywhere from $1.50 to $3.00 per square foot, depending on the type of metal used (e.g. steel, aluminum, etc.).

It´s pertinent to keep in mind that these are just rough estimates, and the actual cost of roof substrates can vary greatly depending on the specific project. It´s best to get a quote froma contractor or supplier to get a more accurate estimate of the cost of roof substrates for your building.

What is an open frame substrate?

An open frame roof substrate is an engineered roof decking material consisting of a system of interlocking beams, panels, and columns. This substrate is often used in the construction of commercial and industrial structures, due to its lightweight, low cost, and easy installation. The open frame roof substrate is designed to provide superior support for roofing systems, as well as improved energy efficiency. It is also designed for fire resistance and wind uplift resistance and serves as a base for insulation. The open frame roof substrate is a reliable, strong, and cost-effective choice for many roofing projects.

Substrate boards vs cover boards

What is the difference? well, substrate board is a structural board used in roofs, walls, floors and ceilings. It is designed to provide stability, strength and rigidity. Cover board, on the other hand, is a non-structural board used for decorative purposes. It is used to cover up other structural materials. Cover board is generally thinner than substrate board and is often used to provide a seamless finish to a wall or other surface. Substrate board and cover board can be used in conjunction with one another, creating a strong and attractive wall, floor or ceiling or other surface.

In conclusion, the roof substrate is a critical component of any roofing system and has a significant impact on the overall performance and longevity of a roof. By considering factors such as cost, weight, moisture resistance, climate, local building codes, compatibility wtih roofing materials, and sustainability, you can choose the right roof substrate for your building.

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