In the construction industry, there are many materials that you’ll be quoted and required to purchase, yet after the construction is complete, you’ll never see them. Consider, for instance, when preparing for the slab work. A constructor requires you to purchase a polythene sheet. This paper is placed under BRC wires to minimize capillary flow, and then concrete is poured. This is a very thin material with a very significant role. It is placed between two materials. This is an example of underlayment.
An underlayment is a thin layer of material sandwiched between other materials. These materials are commonly applied for flooring and roofing systems. Some failures can be attributed to the wrong selection or placement of the underlayment. Consider, for example, a residential building constructed within a swampy environment. Even though the building’s floor is raised several feet above the water base, it turns out that, over time, the floor becomes moist. People have complained of ground-floor houses being too cold. These challenges could have been avoided if a proper underlayment paper had been selected to prevent capillary water flow.
Failures in some buildings can be attributed to hidden factors, such as underlayment failures. Underlayment supports foundation stability while improving the structure’s performance by managing moisture, controlling sound, and regulating thermal conditions in the house. Underlayment materials vary depending on the construction application. While flooring underlayment may seek to manage moisture and sound, roofing underlayment serves to control water flow to the residential space of the building. In short, underlayment supports the structure’s ability to meet minimum human requirements.
This discussion examines the importance of underlayment, the application areas, and how to choose the right underlayment.
Why Is Underlayment Important?
A building without underlayment is vulnerable to failure. Even though the underlayment materials are hidden and sometimes considered idle, they play a critical role in ensuring structural stability and comfort for the inhabitants. The following are some reasons why contractors choose underlayment.
1. Underlayment protects against moisture penetration
Underlayment has moisture-resistant members that prevent water infiltration. Without underlayment, water and moisture can rise through concrete slabs and wood subfloors or fall through roof decking. This water affects sensitive finishes in the room. For flooring, water or moisture accumulation on products such as vinyl, hardwood, and laminate can lead to swelling, adhesive failure, and warping. This affects the house’s decorative status and, sometimes, its structural stability. The prevention of moisture flow helps to protect household property like consumer electronics products.
2. Underlayment improves surface smoothness
Surface smoothness cannot be neglected in structural finishes. Even the best-constructed substrate cannot lack imperfections. Sometimes the substrate may have small depressions, nail heads, uneven joints, and rough surfaces. These imperfections make finishing costly and compromise installation. These imperfections are corrected by underlayment, creating a smooth surface for easy and less costly installation.
3. Reduce noise transmission
In environments such as schools, hospitals, theatres, and offices, noise transmission prevention is necessary. Acoustic underlayment is made from materials like foam and rubber. They help to absorb noise from movements, impacts, and communication. The absorbed noise is later dissipated, keeping the rooms calm.
4. Underlayment enhances thermal insulation
Underlayment helps minimize heat loss from rooms during winter and heat gain during summer. This keeps the rooms comfortable for living. Further, they contribute to energy efficiency by reducing the use of HVAC systems.
5. Underlayment increases structural stability
If the substrate is not well worked, it can have gaps and depressions. These spaces may not ensure uniform distribution of the loads. These load gaps can contribute to deformation, premature wear, and cracking. Underlayment helps to uniformly transmit the loads across the substrate, enhancing structural stability.
There are two common areas of application for underlayment: flooring systems and roofing systems.
Underlayment in Flooring Systems
Underlayment in the flooring systems is placed between the structural subfloor and finished floor covering. The underlayment in flooring systems contributes to comfort, longevity, and performance. Without underlayment in flooring systems, the building can experience moisture damage, flooring failure, and increased noise.
What Are the Main Types of Flooring Underlayment?
Foam Underlayment
Form underlayment is commonly applied in light commercial and residential structures. The materials used to manufacture this underlayment include polypropylene (PP) and polyethylene (PE). This material balances performance, ease of installation, and cost-effectiveness. It is commonly installed under floating floor systems, such as engineered wood and laminate flooring. By cushioning the subfloor and finished flooring, form underlayment regulates noise and standardizes the comfort of the structure for users.
There are several advantages of foam underlayment, making it widely used in flooring systems. First, it is lightweight. The large surface area of this material can be transported with a team of a few professionals. This feature lowers transportation costs and eases the installation process. Second, compared to premium underlayment such as rubber and cork, foam is more affordable. This makes it highly applicable to rental properties. Third, the foam underlayment is well-rolled and can be cut easily with a utility knife. This makes it easy to install, saving on construction time. Further, this material offers good sound reduction. It can noticeably absorb noise from footsteps, chair movements on the floor, and other household activities. This feature is particularly helpful in multi-story buildings, where it reduces sound transfer between floors.
However, foam underlayment presents some limitations. First, it provides limited moisture protection. This implies that engineers must install additional materials in applications such as basements and concrete slabs. Second, it may permanently compress under heavy loads, such as heavy furniture, due to its limited compressive strength. Lastly, foam underlayment has limited application over time. Repeated loading can make it deform, reducing its resilience.
Cork Underlayment
This is a renewable underlayment sourced from the natural environment. It is manufactured from the natural, renewable bark of a cork tree. This underlayment is highly valued by contractors for its exceptional thermal and acoustic properties. Thus, it is widely used beneath tile flooring systems, engineered wood, and laminate.
Cork has a natural cellular structure with millions of microscopic air chambers. These chambers resist heat transfer and offer acoustic features. The cork has a honeycomb-like cell structure, which gives it elasticity. This feature allows it to regain its shape after heavy load compression.
Cork underlayment offers a set of advantages over other types, such as foam, making it a premium option used in high-standard environments. First, its natural occurrence makes it environmentally friendly and renewable. Once cork is harvested from a cork oak, it regenerates, allowing it to be harvested again. Second, its excellent sound insulation properties help absorb airborne sound and impact noise. This leads to a quiet indoor environment free of footstep noise and floor-to-floor vibrations. Third, it offers good thermal insulation properties, reducing heat transfer between rooms and floors.
One limitation of the cork underlayment is its higher cost. Its initial cost is higher than foam’s, because of its natural raw material sourcing, premium acoustic performance, and sustainability certifications. Further, cork requires moisture protection in some environments. Although it is moisture-resistant, it is not completely waterproof. This requires additional materials to support water resistance, especially in water-prone applications such as concrete slabs.
Rubber Underlayment
Rubber underlayment is manufactured from various types of rubber, including natural, synthetic, and recycled rubber. The rubber offers exceptional moisture resistance, acoustic features, and durability. This underlayment is commonly used in educational, healthcare, residential, and commercial buildings. Rubber offers greater resilience and density than foam and cork. This allows it to sustain heavy loading while maintaining performance.
Rubber offers the best properties of the three materials. This material offers excellent noise resistance properties. It is a better moisture-resistant underlayment that protects the flooring systems from mold growth.
Felt Underlayment
This flooring underlayment is manufactured from compressed fibers. The use of recycled content, such as textile, synthetic, and natural fibers, makes felt underlayment sustainable in the construction industry and thus widely adopted. This material is denser than foam underlayment. This relatively higher density makes it more reliable in sound absorption.
The dense, fibrous composition of felt underlayment helps trap air while absorbing impact energy.
Underlayment in Roofing Systems
Common roofing underlayment in the modern construction industry includes asphalt-saturated felt, synthetic roofing underlayment, and rubberised asphalt.
1. Asphalt-Saturated Felt
This underlayment is sometimes called felt paper, roofing felt, or tar paper. It is one of the oldest underlayments and is still widely used in the modern construction industry because of its relatively lower costs. To manufacture asphalt-saturated felt, asphalt is added to organic or fiberglass to saturation. The resulting mixture is water-resistant. Asphalt-saturated felt is placed between the roof deck and the finished roofing material. Sometimes, wind can drive rain into roofing panels. The felt protects the roof deck from this moisture.
Asphalt-saturated felt is widely available and has been used for years. Constructors are familiar with the installation process for this underlayment, making it easy to install. However, the material is heavy and has lower wear resistance.
2. Synthetic Roofing Underlayment
Synthetic roofing underlayment is manufactured from polymers like PP and PE. These underlayment provide superior installation performance, durability, and moisture protection, making them preferred in modern construction.
This underlayment is installed between the roof deck and finished roofing material, protecting a building from water infiltration.
3. Rubberized Asphalt Underlayment
Rubberized asphalt products provide premium waterproof protection, especially for water-leaking vulnerable designs. To manufacture these underlayment materials, engineers modify asphalt with rubber polymers. A reinforced backing layer is added to enhance durability. Rubberized asphalt underlayment is flexible, yet it acts as a barrier against water infiltration. Constructors use this underlayment in roofing zones such as eaves, valleys, and chimneys.
How do different underlayments compare?
The following table summarizes the comparison of different underlayments.
| Underlayment Type | Primary Application | Moisture Resistance | Sound Control | Durability | Relative Cost |
|---|---|---|---|---|---|
| Foam | Laminate Flooring | Moderate | Good | Moderate | Low |
| Cork | Flooring | Moderate | Excellent | Good | Medium |
| Rubber | Flooring | High | Excellent | Excellent | High |
| Felt | Flooring | Moderate | Good | Good | Medium |
| Cement Board | Tile Flooring | High | Limited | Excellent | Medium |
| Asphalt Felt | Roofing | Moderate | N/A | Moderate | Low |
| Synthetic | Roofing | High | N/A | Excellent | Medium |
| Rubberized Asphalt | Roofing | Very High | N/A | Excellent | High |