This question comes up a lot, and the honest answer starts with a correction to how it's usually framed. Solid wood flooring is nailed or glued directly to the subfloor, it isn't a floating floor, which means the thick, cushioned underlay associated with laminate or click-together engineered flooring doesn't really apply to it in the same way.
Why Solid Wood Doesn't Use A Floating-Floor-Style Underlay
Laminate and many click-lock engineered products are floating floors, meaning the boards connect and sit on top of the subfloor without being fixed to it directly. That's exactly why they need a foam or cork underlay, it's the only thing supporting and cushioning the floor from below, since nothing else is anchoring it in place. Solid wood works completely differently: it's fixed directly to the subfloor, either nailed to a wooden subfloor or glued to a concrete one, which means it doesn't rely on a cushioning layer beneath it the way a floating floor does. This is a genuinely important distinction, since the two flooring types solve the "what goes underneath" question in fundamentally different ways.
What Solid Wood Actually Uses Instead
Rather than a thick foam or cork underlay, solid wood installations typically use a thin felt or rosin paper layer between the boards and the subfloor. This serves a different, more modest purpose than a floating floor's underlay: it helps reduce minor wood-on-wood squeaking and provides a light moisture buffer, rather than cushioning or supporting the floor structurally. It's a genuinely different product from the underlay used under laminate, thinner, lighter, and doing a narrower job.
When A Moisture Barrier Becomes Necessary
This is where the original concern behind the "underlay" question genuinely matters, just under a different name. Where solid wood is glued down over a concrete subfloor, excess moisture in the concrete can cause real problems over time, cupping, warping, loose boards, or a chipped finish, if it isn't properly managed. In these cases, a moisture barrier appropriate to the specific subfloor conditions is genuinely important, though this is a targeted moisture-management product rather than a general-purpose cushioning underlay.
Sound Considerations For Solid Wood
It's worth correcting a common assumption here: squeaking in a solid wood floor isn't fixed by adding a cushioning underlay, since the floor isn't floating on one in the first place. Squeaks in a fixed solid wood floor typically come from loose fixing points or subfloor movement, boards that have worked slightly loose from their nails, or a subfloor that flexes under weight. The fix is proper fixing technique and solid subfloor preparation during installation, not an underlay, and if squeaks develop later, addressing the loose boards directly, sometimes alongside professional gap filling, is the genuine solution rather than anything installed beneath the floor.
Engineered Wood Is Different
This is exactly where the confusion tends to come from, since engineered wood genuinely can be installed as a floating floor, and when it is, it does use a proper cushioning underlay, the same category of product used under laminate. Engineered wood can also be nailed or glued like solid wood, depending on the product and subfloor, which is part of why it's such a flexible option. If you're specifically weighing up whether your floor needs a full cushioning underlay, that question depends heavily on whether you're choosing solid wood (fixed, thin membrane only) or engineered wood installed as a floating floor (genuinely needs proper underlay).
Solid Wood And Underlay: Common Questions
Does solid wood flooring need a cushioned foam underlay like laminate does?
No, genuinely not. Solid wood is nailed or glued directly to the subfloor rather than floated, so it doesn't rely on a cushioning underlay the way laminate or floating engineered flooring does.
What does solid wood use instead of underlay?
Typically a thin felt or rosin paper layer, which helps reduce minor squeaking and provides a light moisture buffer, a genuinely different, thinner product than a floating floor's cushioning underlay.
Does a solid wood floor need a moisture barrier over concrete?
Often yes, if it's being glued down over a concrete subfloor with any moisture concern. This is a targeted moisture-management product, though, not a general cushioning underlay.
Will adding underlay stop my solid wood floor from squeaking?
No, since solid wood isn't floating on an underlay in the first place. Squeaks come from loose fixing points or subfloor movement, and the real fix is addressing those directly, not adding a cushioning layer.
Call us on 020 7036 0625 or request a free site visit and we'll advise on the right subfloor preparation for your specific solid wood or engineered wood project.
