Laying underlay is a crucial step when installing new flooring, whether it’s carpet, laminate, vinyl, or hardwood. The underlay provides cushioning, sound insulation, and thermal benefits, while also helping to level the subfloor and extend the life of your flooring. Doing this job properly ensures a smoother, longer-lasting finish and reduces wear on the visible flooring material. With the right preparation and a methodical approach, you can lay underlay effectively even if you’re a beginner at DIY flooring projects.
Understanding the Purpose of Underlay
Before beginning, it’s important to understand why underlay is essential. Not all floors require the same type of underlay, and choosing the correct one will enhance the performance of your floor.
Main Benefits of Using Underlay
- Improves comfort underfoot
- Reduces noise between floors
- Provides thermal insulation
- Acts as a moisture barrier (especially for laminate and wood)
- Helps absorb impact and reduce wear on the surface flooring
Different flooring types carpet, laminate, vinyl, engineered wood will each need specific underlay characteristics, such as density, thickness, and moisture resistance.
Types of Underlay
Selecting the right underlay depends on the flooring material and the conditions of the room where it will be installed. For example, underfloor heating requires specialized thin underlay, while basement floors may need a moisture-resistant type.
Common Types of Underlay
- Foam underlay: Lightweight, budget-friendly, and ideal for laminate or engineered wood flooring.
- Rubber underlay: High durability and soundproofing qualities, suitable for carpet or wood floors.
- Felt underlay: Dense and durable, often used for traditional carpet installations.
- Combination underlay: Offers both moisture protection and cushioning, ideal for concrete subfloors.
Once the correct type is selected, it’s time to start the installation process step by step.
Preparing the Subfloor
The subfloor must be clean, dry, and level before installing any underlay. Preparation is key to a successful and lasting flooring installation.
Steps for Subfloor Preparation
- Remove old flooring and adhesives completely.
- Vacuum or sweep to remove dust, dirt, or debris.
- Check for dampness especially on concrete subfloors.
- Use a level to check for high or low spots. Fill or sand as needed.
- Ensure all screws or nails are flush with the subfloor surface.
If your subfloor is uneven, use a self-leveling compound for smoothing. Allow it to dry fully before proceeding to the next steps.
Tools and Materials Needed
Having the right tools and materials ready will make the job go faster and more efficiently. Most materials can be found at a home improvement store.
Basic Tools for Laying Underlay
- Utility knife or underlay cutter
- Measuring tape
- Underlay adhesive or tape (depending on floor type)
- Staple gun or hammer tacker (for carpet underlay)
- Moisture barrier (if required)
- Ruler or straight edge for cutting
Ensure you wear knee pads or use a kneeling pad for comfort while working on the floor for extended periods.
How to Lay Underlay for Different Flooring Types
The process varies slightly depending on whether you’re laying underlay for carpet, laminate, or vinyl. Below are step-by-step instructions for the most common types.
For Carpet
- Roll out the underlay with the paper or backing side up.
- Lay it wall-to-wall, allowing a little extra on all edges for trimming.
- Staple or tack the underlay at the perimeter and seams.
- Trim the edges so it sits snug against the walls.
- Tape all seams with underlay tape to prevent movement.
Make sure the joins between rolls do not overlap, and avoid stretching the material too tightly, which can cause unevenness under the carpet.
For Laminate or Engineered Wood
- Begin at one corner of the room, rolling the underlay parallel to the longest wall.
- Lay each strip tightly side by side without overlapping.
- Use underlay tape to secure seams.
- Install a moisture barrier first if required, especially on concrete subfloors.
- Ensure underlay doesn’t bunch or wrinkle before laying the flooring over it.
If using underlay with an attached moisture barrier, overlap the barrier portion at seams and tape it to seal.
For Vinyl or LVT (Luxury Vinyl Tile)
Many vinyl and LVT products come with a built-in underlay, but if you need to install one separately:
- Use a very thin, high-density underlay suitable for vinyl.
- Lay it flat and tape all seams securely.
- Avoid any raised seams or bumps, which can show through the flooring.
- Check the manufacturer’s recommendation to ensure compatibility with the vinyl type.
Do not use soft or springy underlays with vinyl, as they may damage the flooring or affect the installation integrity.
Trimming and Finishing Touches
Once all the underlay is laid and secured, trim around the edges of the room and obstacles such as pipes, door frames, or alcoves. A utility knife works well for precise cuts.
Key Final Steps
- Ensure the underlay fits neatly with no bulges or gaps.
- Double-check that all seams are securely taped or stapled.
- Cut any excess underlay near walls or thresholds.
- Allow the underlay to settle for a few hours before installing the top flooring, if possible.
Proper trimming ensures a smooth, seamless finish and helps the top layer of flooring lie flat.
Common Mistakes to Avoid
Even with the right tools and instructions, there are a few common errors that can affect your results. Knowing what to avoid can save time and money.
- Overlapping underlay: This causes bumps under the flooring.
- Skipping moisture barrier: Especially dangerous on concrete subfloors.
- Poor trimming: Leads to bunching or gapping.
- Using the wrong underlay: Not all underlays are universal; check compatibility.
- Not securing seams: Unfastened underlay can shift during floor installation.
Learning how to lay underlay is a valuable skill for any home improvement enthusiast. Whether you’re installing carpet, laminate, or vinyl, the right underlay will enhance your floor’s comfort, insulation, and durability. With the correct materials, tools, and a bit of patience, you can complete this step with professional-level results. Proper underlay installation sets the foundation for a beautiful and lasting floor that you can enjoy for years to come.