How to Fasten Underlayment to Subfloor

Installing new flooring is an exciting home upgrade that can breathe new life into any room. However, one crucial step often overlooked is properly fastening the underlayment to the subfloor. So, do you know how to fasten underlayment to subfloor?

In this guide, we’ll explore the step-by-step process of fastening underlayment to a subfloor, covering the necessary tools, materials, and techniques to help you complete the task efficiently and accurately. Following the instructions will enable you to tackle your flooring project and achieve a durable and long-lasting result.

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Understanding Underlayment and Its Importance

Underlayment, a thin layer placed beneath flooring, serves several essential purposes. It shields against moisture, reduces sound, provides insulation, and ensures a smooth surface for installation. 

Foam underlayment is suitable for laminate and engineered hardwood floors, offering basic moisture protection and sound reduction. Rubber underlayment is particularly effective in controlling noise and can be used with various flooring materials. 

Furthermore, cork underlayment, known for its eco-friendliness and resistance to mold, is an excellent choice for hardwood and vinyl flooring. Felt underlayment provides moisture protection and sound absorption, making it ideal for hardwood floors. 

Moreover, combination underlayment blends different materials to enhance performance, catering to various flooring types and installation requirements. Hence, selecting the appropriate underlayment is crucial for maintaining the integrity and performance of your flooring in the long run.

Tools and Materials Needed

The right tools and materials are essential before starting any underlayment installation. Not only will this ensure the job gets done efficiently, but it will also help prevent delays and frustration.

List of tools

• Utility knife with extra blades
• Chalk line reel or straight edge
• Tape measure
• Hammer or nail gun (if using nails)
• Drill (if using screws)
• Saw (jigsaw, circular saw or handsaw)
• Pry bar
• Caulk gun (if using construction adhesive)

List of materials

• Underlayment panels (plywood, OSB, cement backer board, etc.)
• Fasteners (nails, screws or construction adhesive appropriate for underlayment type)
• Vapor barrier (if required by local codes)
• Joint tape or caulk (for seams if required)

Safety equipment needed

Safety should always be a priority when tackling home projects. Remember to wear eye protection, ear protection (if using power tools), a dust mask or respirator, gloves, and sturdy shoes or work boots. 

Additionally, make sure you have a level work surface and adequate lighting. Being prepared with all necessary items before you begin will help ensure a smooth underlayment installation.

Choosing the right underlayment material

The type of underlayment you use depends on the finished flooring being installed on top and the subfloor condition. Common options include:

• Plywood or OSB for laminate, hardwood, tile floors
• Cement backer board for tile installations
• Foam or cork underlayment rolls over existing floors

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Preparing the Subfloor

To ensure a smooth floor installation, it’s essential to properly prepare the subfloor surface before installing the new underlayment. This preparation ensures the underlayment lays flat and securely adheres, resulting in a seamless finish.

Cleaning the subfloor

We recommend you start by thoroughly cleaning the entire subfloor area using a broom or vacuum to remove any dust, dirt, or debris. Also, sweep or vacuum thoroughly along the edges and in corners.

Checking for levelness

Next, check the subfloor for level by using a straight edge or long level in several locations across the room. Identify any high or low spots that need addressing. An unlevel subfloor may cause the underlayment panels to flex and potentially crack over time.

Repairing damages

You need to examine the subfloor carefully. If you find any damage, fix it promptly. For small cracks or holes, apply a flooring patch compound. 

If you notice raised nails or screw heads, gently tap them down until they are below the surface. For sections of the subfloor that are severely damaged, replace them with new panels.

Ensuring subfloor dryness and debris-free surface

To ensure the underlayment sticks well, it’s crucial to start with a dry, clean surface. You can use a moisture meter to make sure the moisture levels are okay. For wood subfloors, it’s best if the moisture content is below 12%.

Once you’ve fixed any problems and the subfloor is dry and clear of debris, it’s time to prepare for the underlayment. This preparation step is important. It helps to avoid problems like squeaks, gaps, or damage to the underlayment.

Choosing the Right Underlayment

Choosing the right underlayment is crucial for a smooth floor installation. You should consider factors like the type of finished flooring you’ll use, how much moisture is in the area, the condition of the existing subfloor, whether you need sound insulation, and how the room will be used.

Matching underlayment to flooring material

For hardwood floors, use plywood or oriented strand board (OSB) underlayment. With laminate floors, install foam or cork underlayment over plywood or OSB. But do you staple underlayment for laminate flooring? 

Yes, you can staple underlayment for laminate flooring. However, it’s important to check the manufacturer’s recommendations for the specific type of underlayment you’re using, as some may require different installation methods.

Additionally, tile floors require cement backer board underlayment over plywood subflooring. For vinyl floors, foam or cork underlayments work well. We advise you to always check the manufacturer’s recommendations.

Addressing specific needs of the area

Underlayments with moisture barriers are essential in moisture-prone areas such as bathrooms. Similarly, basements need underlayment with vapor barriers to prevent moisture from seeping.

For living areas, it’s advantageous to use sound-dampening underlayments to reduce noise transfer. Additionally, if you’re installing over radiant heat, it’s crucial to use underlayments specifically rated for that purpose.

The perfect underlayment takes into consideration various factors, such as the type of flooring, the condition of the subfloor, moisture exposure, sound insulation requirements, and the intended use of the room. This ensures proper support and protection for your flooring.

How to Fasten Underlayment to Subfloor

Once you’ve chosen the right underlayment and prepped the subfloor, it’s time to install it. Properly securing the underlayment panels is key to achieving a smooth, squeak-free base for your new flooring.

Start by making sure the subfloor is clean and smooth. Lay the underlayment down, overlapping seams if needed, then use a staple gun or nails to fasten it to the subfloor.

Secure the underlayment every few inches along the edges and throughout the middle to keep it in place. Be careful not to drive the staples or nails too far, and trim any excess underlayment around the edges for a tidy finish. 

This process creates a sturdy foundation for your flooring and prevents shifting or damage over time. Now, we elaborated further in the sections below.

Starting point

Always begin underlayment installation along the most straightforward wall. This allows you to stagger end joints in each row. Stagger underlayment panel end joints by at least 16 inches from the adjacent row.

For the first row, place underlayment panels with the grooved edge facing the wall. Allow a 1/4-inch gap along all walls for expansion. Underlayment edges should be flush with no gapping.

Securing methods

There are three common methods for fastening underlayment to wood subfloors:

Using staples

An underlayment stapler using 16-gauge divergent staples is perfect for fastening panels efficiently. Place staples 3-4 inches apart along the edges of the panels and 8 inches apart within the field, between joists. We advise you to avoid nailing or stapling underlayment directly onto joists.

Using nails

We recommend ring shank or deformed shank nails for underlayment installation. They provide superior holding power compared to smooth nails. 

Use nails 1 to 1-1/4 inches long to ensure proper installation. Place the nails 6 inches apart along the edges of the underlayment and 8 inches apart in the middle. Make sure to keep the nails at least 3/8 inch away from the panel edges to avoid surface cracking.

Using screws

For an extra-secure installation, use underlayment screws designed for wood application. Drive screws at a 45-degree angle through the underlayment and into floor joists. 

Make sure to space the screws evenly, placing them 12 inches apart along each joist. Additionally, ensure that the screw heads are flush with the surface, avoiding over-driving them.

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Dealing with seams

To maximize strength, stagger the end joints of all underlayment panels. Ensure that the gaps between panels do not exceed 1/32 inch. 

When dealing with tongue-and-groove panels, use a flooring scraper or trowel to connect the grooved edges fully. For added stability, apply a bead of tongue and groove adhesive along the joint.

Avoiding common mistakes

Avoid putting underlayment panels straight across joists, as this may strain the material and prevent correct installation. Instead, stagger end joints by at least 16 inches to prevent seams from aligning.

Make sure to drive fasteners flush with the surface, without over-driving them, to prevent dimpling. Also, steer clear of spacing fasteners too far apart, as this can cause panel movement and create squeaks.

Moreover, always leave a 1/4-inch gap at walls and obstructions to allow for expansion. Neglecting this step could lead to ridges or buckling as the underlayment expands. By adhering to these best practices for fastening underlayment, you’ll establish a flat and secure base perfect for applying finished flooring.

Conclusion

Understanding the recommended fastening methods, whether staples, nails, or screws, is crucial while learning how to fasten underlayment to subfloor. Knowing how to properly stagger seams and allow for expansion is also essential for a stable and squeak-free base for your new floors.

With our tips and easy steps in mind, you can take on your project with confidence. You will provide a reliable underlayment foundation that will support your finished flooring for years to come.