Engineered Wood Flooring Thickness: 12 to 20 mm
What 14, 15, 18 and 20 mm engineered boards are made of, what thickness changes over joists and underfloor heating, and why the wear layer matters more.
Engineered oak is sold by thickness first, and the number is easy to over-read. A thicker board is not automatically a better one; it is a different construction for a different job. The engineered floors in our range come in five thicknesses: 14 mm in 44 cases, 18 mm in 8, 15 mm in 6, 20 mm in 6 and 12 mm in one. This guide explains what the total thickness is made of, what it changes, and where the wear layer and the width matter more.
The five thicknesses in the range
Thickness and the wear layer are different numbers
Read together, the list shows that thickness does not decide the wear layer. At 18 mm there are 3 mm and 4 mm layers; at 20 mm, 4 mm and 6 mm. It is the wear layer that decides how many times a floor can be sanded, and the only sourced figure for that comes from a manufacturer, Kährs, which says engineered floors can be sanded up to four times depending on the thickness of the wear layer. If refinishing over decades is the point, compare wear layers, not total thickness.
Thickness over joists and battens
Where the floor goes over joists or battens rather than a screed, thickness becomes structural. BEAMA, the UK underfloor heating trade association, advises in its guidance on floors over heating that, unless installed over a screeded slab, engineered boards of less than 20 mm thickness should be supported and fixed to an additional decking material, unless the manufacturer specifically states otherwise. In our range 59 of the 65 engineered floors are thinner than 20 mm. BEAMA also describes engineered timber as something that can be laid as a floating floor or nailed into battens or joists; which of those a particular board allows is set by its fitting instructions.
Thickness over underfloor heating
Every engineered floor in our range is listed as compatible with underfloor heating, at every thickness. What thickness changes is how much heat the floor holds back. Floor coverings over a water-based system are normally limited to 0.15 m²K/W, and Junckers, a maker of hardwood floors, publishes the figures for its own boards: 0.08 m²K/W at 14 mm, 0.09 at 15 mm and 0.12 at 20.5 mm. Those are one manufacturer's numbers, not a property of every board, but they show the direction: a thicker board leaves less of the allowance for the underlay.
Width is the other dimension
Thickness is rarely what changes the look of a room; width is. Wood moves mostly across its width: the Handbook says it shrinks and swells most in the direction of the growth rings and only slightly along the grain. The wide plank page gathers the engineered boards from 190 mm up, and the guide to wide and narrow planks covers what width does to a room and to the way a floor moves.
Common questions
What thickness of engineered wood should I choose?
For most rooms over a screed, the 14 mm boards that make up most of our range, 44 of the 65 engineered floors. Go thicker for a reason: a particular herringbone block, a thicker wear layer, or a floor over joists, where BEAMA advises an additional deck under engineered boards thinner than 20 mm.
Is 14 mm engineered wood thick enough?
Over a flat screed, yes: it is the thickness of 44 of our 65 engineered floors, almost all with a 3 mm oak wear layer. Over joists or battens, BEAMA advises fixing engineered boards thinner than 20 mm to an additional deck unless the manufacturer states otherwise.
Is 20 mm engineered wood better than 14 mm?
Not better, different. Our 20 mm floors carry a 4 or 6 mm wear layer against 3 mm on most 14 mm boards, and at 20 mm BEAMA's rule for an additional deck over joists no longer applies. Over underfloor heating it holds back more heat: on Junckers' published figures 0.12 m²K/W at 20.5 mm against 0.08 at 14 mm.
Does thickness matter for underfloor heating?
Not for compatibility: all 65 engineered floors in our range are listed as compatible. It matters for heat output, because a thicker board takes more of the 0.15 m²K/W normally allowed for the floor covering, leaving less for the underlay.
Is the wear layer the same as the thickness?
No. The thickness is the whole board; the wear layer is the oak on top. At 18 mm our range has 3 mm and 4 mm wear layers, at 20 mm 4 mm and 6 mm. The wear layer decides how often the floor can be sanded.
Every product page states thickness, width, length and wear layer. We deliver engineered oak town by town across the UK. Browse by town and region.
