18mm Engineered Wood Flooring

Thickness	Best For	Underfloor Heating	Sanding Capacity	Typical Price/m²
14mm	Bedrooms, low-traffic areas	✅ Excellent	1-2 times	£30-45
15mm	Living rooms, medium traffic	✅ Good	2-3 times	£35-50
18mm	High-traffic areas, family homes	✅ Compatible	3-5 times	£40-70
20mm	Commercial, luxury projects	⚠️ Check specs	4-6 times	£60-100+

* 18mm offers the best "sweet spot" for most UK homes—thick enough for durability, optimal for underfloor heating.

Dan's Take On 18mm Engineered Flooring

Over the last 9 years, the Flooring365 team has supplied and advised on over 20,000 18mm engineered wood projects across the UK. Here's what we've learned:

Underfloor heating works brilliantly with 18mm—provided the wear layer doesn't exceed 5mm. Thinner wear layers conduct heat 15-20% more efficiently.
Acclimatisation is non-negotiable. We recommend 72 hours minimum for 18mm boards. Skipping this step is the #1 cause of post-installation gaps.
Mixed-length boards (300-1200mm) create the most natural look. Our 18mm range includes both fixed and mixed lengths—check product specs below.

— Dan, Flooring365 Product Specialist

Installing 18mm Engineered Wood Flooring

Acclimatisation Requirements

Duration: 72 hours minimum for engineered wood (longer in winter months)
Conditions: 40-60% relative humidity, 18-22°C temperature (60-80°F)
Placement: Keep in original packaging, stack loosely, store flat in the installation room with air circulation around all sides

Pro tip: For a minimum of several days prior to installation, the room should have stable conditions with permanent HVAC operating. The goal is to reach equilibrium moisture content (EMC) where boards are neither gaining nor losing moisture. In new construction, wood flooring should be one of the last items installed, after all "wet" works (plastering, painting) are completed and fully dried.

Subfloor Preparation

Flatness: Must be ≤3mm variance over 3 metres (or 2mm over 2 metres)
Moisture: Concrete subfloors need moisture testing—below 75% relative humidity for floating installations (impedance meter readings up to 2.0%)
Underlay: 3mm underlay standard for 18mm boards; use 5mm only if additional soundproofing needed for noise control in apartments or multi-family dwellings
Cleanliness: Subfloor must be clean, dry, structurally sound, and free of dirt, debris, or protruding fasteners

Concrete subfloor note: Concrete substrates should be cured for at least 60 days before installation. For floating installations over concrete, always use an underlay with a moisture barrier.

Expansion Gaps

Always leave 10-15mm expansion gap around walls and fixed objects. For engineered hardwood specifically, 12mm (1/2") is recommended as the standard gap. 18mm boards expand slightly less than solid wood, but movement still occurs with changes in humidity and temperature.

Perimeter gaps: Minimum 10mm for engineered wood, 12mm (1/2") recommended for optimal protection
Large rooms: For rooms exceeding 12m in length or 8m in width, additional expansion breaks with T-moldings are required
Door frames: Always leave expansion gap and undercut door jambs so flooring slides underneath for a clean look
Fixed objects: Don't forget expansion around pipes, columns, kitchen islands (never pin the floor under fixed furniture), and transition moldings

Final step: After installation, remove all expansion spacers before installing skirting boards or beading. Cover expansion gaps with skirting boards or scotia/quarter round, fixing them to the walls—not the floor, so the floor can still move freely.

Technical References & Sources ▼

Frequently Asked Questions About 18mm Engineered Wood

Can 18mm engineered wood flooring be installed over underfloor heating? ▼

Yes, 18mm engineered wood is compatible with underfloor heating, but only with water-based systems. Electric underfloor heating can overheat and damage the boards. For optimal performance, choose boards with a wear layer of 5mm or less to ensure efficient heat transfer. Maintain a consistent surface temperature between 18-27°C and never exceed 27°C.

How many times can 18mm engineered wood be sanded and refinished? ▼

With a typical wear layer of 4-6mm, 18mm engineered wood can be sanded 3-5 times over its lifetime. This gives the floor a total lifespan of 25-30+ years with proper maintenance. Each sanding removes approximately 0.5mm of material, so check your specific product's wear layer specification.

What expansion gap is needed for 18mm engineered wood flooring? ▼

Always leave an expansion gap of 10-15mm around walls, door frames, and fixed objects. While 18mm engineered wood is more stable than solid wood, it still expands and contracts with humidity changes. This gap can be covered later with skirting boards or beading.

Is 18mm thick enough for high-traffic areas like hallways and living rooms? ▼

Absolutely. 18mm engineered wood is the ideal thickness for high-traffic areas in family homes. The substantial construction provides excellent durability and a solid feel underfoot, making it suitable for hallways, living rooms, open-plan spaces, and even light commercial use.

Do I need underlay for 18mm engineered wood flooring? ▼

It depends on your installation method and subfloor:

Floating installation (click system): Yes—use a 3mm underlay for sound reduction and moisture protection.
Fully adhering (glue-down): No separate underlay needed.
Apartments: Consider acoustic underlay to reduce noise transmission to neighbours.

Can 18mm engineered wood be installed in kitchens or bathrooms? ▼

Yes, 18mm engineered wood can be installed in kitchens and bathrooms with proper precautions:

Ensure good ventilation
Immediately wipe up any spills
Maintain consistent humidity (40-60%)
A factory-finished lacquered surface offers better moisture resistance

What's the difference between 14mm, 15mm, 18mm, and 20mm? ▼

14mm: Bedrooms/low-traffic, sandable 1-2 times, £30-45/m²
15mm: Living rooms/medium traffic, sandable 2-3 times, £35-50/m²
18mm: High-traffic family homes, sandable 3-5 times, UFH compatible, £40-70/m²
20mm: Luxury projects, sandable 4-6 times, check door clearances, £60-100+/m²

How long does 18mm engineered wood need to acclimatise? ▼

Minimum 72 hours required. Place unopened boxes in the installation room with stable conditions: 40-60% humidity and 18-22°C temperature. In winter or with high-moisture subfloors, extend to 5-7 days.

Can 18mm engineered wood be installed on concrete? ▼

Yes, with options:

Floating: Lay over underlay with moisture barrier
Glue-down: Fully adhere with flexible adhesive

Test concrete moisture first—must be below 75% relative humidity.

How do I maintain and clean 18mm engineered wood? ▼

Daily: Sweep or vacuum with soft brush
Deep clean: Damp mop with pH-neutral wood cleaner
Avoid: Steam mops, excessive water, abrasive cleaners
Protect: Felt pads under furniture, mats at entrances

Oiled or lacquered finish—which is better? ▼

Oiled: Natural look and feel, easier spot repairs, needs oiling every 6-12 months
Lacquered: Protective surface, stain-resistant, lower maintenance, cannot spot-repair

Choose based on lifestyle: oiled for natural aesthetics, lacquered for durability.

Is 18mm engineered wood suitable for DIY installation? ▼

Yes for click-lok systems—they're designed for DIY. Tongue and groove boards typically need professional installation (glue-down or secret nailing). Ensure subfloor is level (≤3mm variance over 2m) and follow acclimatisation guidelines.

18mm Engineered Wood Flooring