Achieving Proper Expansion Gaps for Engineer (Explained)

Engineered hardwood flooring has become an increasingly popular choice for homeowners due to its durability, ease of installation, and visual appeal. However, improper installation can lead to buckling, gapping, or failure of the flooring system.

One of the most important installation steps is allowing for proper expansion space around the perimeter of the flooring. This article will provide a comprehensive guide on best practices for engineered hardwood floor expansion gaps.

Engineered hardwood consists of multiple layers of wood pressed together. The top layer is made of solid wood, while the bottom layers are comprised of plywood or high-density fiberboard.

This construction makes engineered flooring more dimensionally stable than solid hardwood, meaning it resists expansion and contraction due to changes in temperature and humidity. However, expansion and contraction still occurs to some degree, so allowing for proper expansion space is crucial during installation.

When inadequate expansion space is left around the perimeter and at flooring transitions, the wood cannot freely expand and contract. This leads to buckled or gapped flooring or failure of the locking system. Leaving proper expansion gaps allows the flooring space to move naturally without causing damage. Getting expansion gaps right is one of the most vital aspects of engineered flooring installation.

An adequate expansion gap helps prevent:

  • Buckling or peaking of flooring
  • Gaps forming between boards
  • Locking system failures
  • Damage to the subfloor
  • Creaking and popping sounds

This article will cover the fundamentals of allowing for proper expansion when installing engineered hardwood. Key topics include:

  • How expansion and contraction works with engineered wood flooring
  • Recommended expansion gaps for perimeter and transitions
  • Tips and guidelines for calculating gap size
  • Methods for covering the expansion gap
  • Troubleshooting buckling and gapping issues
  • Preventing expansion-related problems during installation

Correctly providing for expansion results in an engineered floor that performs well for years to come. Pay close attention to expansion joints during the installation process to avoid unnecessary flooring failures down the road.

How Expansion and Contraction Works with Engineered Wood Floors

To understand why adequate expansion gaps are mandatory, it’s important to comprehend how expansion and contraction affects engineered flooring.

The key facts are:

  • Humidity causes wood to swell; low humidity causes wood to shrink. Even though engineered flooring is more stable than solid wood, changes in humidity still impact the dimensions of the boards.
  • Temperature fluctuations also lead to minor expansion and contraction. Higher temperatures cause the boards to expand slightly; cooler temperatures lead to slight shrinking.
  • The expansion and contraction occurs across the width of the boards, not the length. As humidity rises, the boards expand in width, and as it drops, they shrink in width. Lengthwise expansion is minimal.
  • Engineered wood can expand and contract up to 1/2 inch per 100 feet. The exact amount depends on the climate, flooring width, and thickness. Wider and thicker boards expand and contract more than thinner floors.
  • Planks expand and contract individually and at different rates. Each board reacts uniquely to humidity changes.
  • The expansion and contraction is restrained at the perimeter. Since the outer flooring boards are partially constrained by the walls, an expansion gap is needed to allow movement.

In summary: Even though engineered floors are more stable than solid wood, they still expand and contract across their width in reaction to humidity fluctuations in the environment. The perimeter planks have limited expansion, creating the need for adequate expansion gaps.

Recommended Expansion Gaps

Now that we’ve covered the basics of engineered wood expansion, we can move on to specific recommendations for allowing enough space. The National Wood Flooring Association (NWFA) provides the following guidelines:

Perimeter Gap

  • Leave at least 1/2 inch expansion gap around the entire perimeter of the flooring.
  • Make the gap equivalent to the thickness of the flooring boards. For example, 3/8 inch thick boards require a 3/8 inch perimeter gap.
  • For rooms larger than 1,000 square feet or flooring wider than 5 inches, allow slightly larger perimeter gaps. Add an extra 1/16 inch for every additional 3 feet in room width beyond 33 feet.

Transition Gap

  • Provide a minimum 1/2 inch expansion gap at all floor transitions.
  • This includes doorways, openings to other rooms, connections with tile, thresholds, stairs, fireplaces, etc. Anywhere the new flooring terminates, leave ample room for expansion.
  • As with the perimeter, make the transition gap the same thickness as the flooring boards.

These recommended gaps are minimums; using slightly wider gaps is always safe. Proper expansion joints help prevent the frustrations of buckling or gapping flooring.

Calculating Gap Size

NWFA guidelines provide the basic expansion gap dimensions, but several factors can influence the ideal width:

  • Flooring width – Wider boards expand/contract more. Add 1/16 inch gap for each additional 2 inches of flooring width.
  • Flooring thickness – Thicker floors move more than thinner ones. Add 1/16 inch for each 1/32 inch increase in thickness.
  • Room size – Larger spaces need wider gaps (1/16 inch more per 3 feet over 33 feet room width).
  • Climate – Floors in hot, humid environments should get wider gaps.
  • Direction – Run the flooring perpendicular to joists to minimize gapping.
  • Subfloor – Concrete slabs warrant slightly bigger gaps than wood subfloors.
  • Load – Heavily trafficked floors expand more.

Use these variables to fine-tune gap width. When in doubt, always round up to the next 1/16 inch increment for safety.

Covering the Expansion Gap

The expansion gap leaves an unsightly open space between the flooring and the walls. This gap needs covered with a coordinating trim piece, such as quarter round or baseboard molding.

Tips for trim installation:

  • Select trim wood in the same species as the flooring for visual consistency.
  • Stain or finish the trim to match the floor color. Test on scrap pieces first.
  • Attach the trim to the walls only, not the flooring. This allows the floor freedom to expand.
  • Pre-drill and countersink all trim nails and screws to prevent splitting the wood.
  • Maintain a 1/16 inch gap between the trim piece and flooring to accommodate movement.
  • Use trim pieces long enough to allow for shrinkage during seasonal gaps. Cutting pieces too short can lead to exposed gaps during low humidity.

Installing coordinating trim properly ensures the floor can expand and contract within the gap yet maintain an attractive, finished appearance.

Troubleshooting Buckling and Gapping

What happens when expansion gaps aren’t adequate during installation? Buckled or gapped flooring and failure of the locking system. Here are tips for troubleshooting these unfortunate issues:

Buckling (peaking)

Flooring buckles and lifts off the subfloor when expansion pressure builds. Moisture is usually the culprit. Solutions include:

  • Immediately reduce humidity levels and improve climate control.
  • Temporarily weight down buckled areas until they lay flat again.
  • If buckling persists, disconnect and reinstall affected boards with proper expansion gaps.


Wide gaps form between boards as natural humidity drops. Remedies involve:

  • Increase humidity immediately, use humidifiers if the climate is very dry.
  • During low humidity seasons, fill gaps with coordinating wood filler. Remove and reapply annually.
  • Severe gapping may require reinstalling the flooring with adequate perimeter/transition gaps.

Both buckling and gapping should decline after addressing the expansion space issue. Don’t hesitate to call in a professional if problems continue.

Preventing Problems During Installation

Let’s shift focus to avoiding expansion-related problems proactively during installation:

  • Carefully measure room dimensions and calculate gap widths needed. Remember to factor in board width, thickness, space size, climate, etc.
  • Allow a slightly wider gap than the minimum requirement. It provides a safety margin.
  • Use spacers or shims when fastening the first row of boards to ensure an accurate perimeter gap. Leave spacers in until installation is complete.
  • Follow the same spacing steps for all flooring transitions in doorways and openings.
  • Test the locking system and make sure boards fit snugly, but move freely before fastening. Recheck fit after installing several rows.
  • Acclimate all flooring on-site 72 hours prior to installation. Allow materials to adjust to the interior environment.
  • After installation, maintain indoor humidity between 35-55% year-round. Monitor conditions and adjust as needed.

With attention to proper expansion gaps throughout, engineered hardwood floors provide years of trouble-free beauty and enjoyment. They account for the natural movement of wood yet remain securely fastened and pleasing to the eye.


Allowing engineered hardwood floors adequate room for expansion and contraction is critical for preventing common problems like buckling, gapping, and locking system failures. Follow the recommended guidelines for sufficient perimeter and transition gaps based on the flooring dimensions and environmental factors. Account for the wider expansion of large spaces, wide boards, and variable climates.

Use shims during installation to accurately set gaps, and always allow a margin of error with slightly larger spaces. Cover gaps neatly with coordinating trim pieces affixed only to the walls, not the flooring. This enables free expansion within the allotted space.

Understand that minor gapping may still occur seasonally as humidity fluctuates. Keep the environment within 35-55% RH year-round to minimize expansion and contraction. With the proper care taken at installation, engineered hardwood floors will perform their best for many years of stylish durability.

The full process includes:

  • Learning how expansion and contraction affects engineered wood
  • Following guidelines for perimeter and transition gap minimums
  • Fine-tuning gap widths based on flooring details and climate
  • Allowing extra margin with slightly oversized gaps
  • Using spacers to accurately set gaps during installation
  • Covering gaps cleanly between floors and walls with trim
  • Maintaining proper humidity and refilling seasonal gaps
  • Contacting professionals promptly if buckling or gapping persists

No cutting corners on the expansion gaps! An attractive engineered floor free of bulges and gaps depends on allowing space for the natural movement of the boards. With a meticulous installation and some simple maintenance, engineered hardwood floors stay securely interlocked and visually pleasing for decades.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *