Ultimate Guide to Installing Water Resistant Laminate with Attached Underlayment

When you choose water-resistant laminate flooring with attached underlayment, you combine comfort, performance, and simplified installation. But success starts with proper preparation and execution. This guide walks you step-by-step through the key installation principles so your floor performs beautifully and lasts for years.

Understanding the Product

Water resistan laminate with pre-attached underlayment is designed for interior use across above-grade, on-grade, and below-grade settings. While the product resists moisture at the surface, it still requires correct subfloor preparation and moisture control to protect the core and prevent installation issues.

Pre-Installation Steps

Before you install, inspect and prepare the space:

• Inspect Each Plank: Check for defects before installation.

• Clean and Level Subfloors: Subfloors must be clean, dry, and level to within 3/16" over 10 feet. 

• Moisture Control: Install a 6 mil polyethylene moisture barrier over concrete substrates to protect against ground moisture. 

• Acclimation: If relative humidity in the room is outside normal ranges, place unopened boxes on-site for 48 hours to equalize temperature and humidity. 

Throughout preparation, remove old flooring such as carpet or loose resilient material, and ensure HVAC is operational with a consistent installation temperature. 

Installation Best Practices

Once the site is ready, follow these foundational steps:

1. Plan Your Layout: Decide plank direction and calculate needed materials. Mark a straight working line to guide installation.

2. Expansion Space: Maintain a gap (often ~⅜") between the floor edges and walls to allow for natural expansion and contraction. 

3. Locking Boards Together: With the grooves facing the starting wall, fit planks sequentially, carefully locking tongues into grooves. 

4. Stagger Seams: Offset end joints in adjacent rows (e.g., at least 8" apart) to provide stability and a natural appearance. 

5. Transition and Trim: Install moldings, thresholds, and baseboards after removing spacers. 

Laminate installations with attached underlayment eliminate the need for separate padding, making the process faster and reducing the risk of over-underlaying, which can compromise locking profiles. 

Final Tips for Success

• Never install your new water resistant laminate over additional underlayment beyond the attached layer unless explicitly allowed by the manufacturer's instructions. 

• Always check subfloor moisture and levelness before starting—it’s the single biggest factor in long-term performance.

• Consult local building codes if you are unfamiliar with moisture control measures.

For the complete, detailed installation manual from McMillan Floors, including tools list, detailed diagrams, and full warranty instructions, see the official PDF here.