Getting this part right matters more than it might seem — most flooring failures trace back to what's underneath the floor, not the floor itself.
Choosing the Right Underlay
The right underlay does three jobs at once: it deadens sound, evens out minor subfloor imperfections, and — where it has a built-in damp proof membrane (DPM) — protects the floor above from moisture coming up through the subfloor. Not every underlay includes a DPM, so it's worth checking this specifically rather than assuming it's covered, particularly on ground-floor concrete subfloors.
Acoustic performance is usually given as a decibel reduction figure, and this matters most in flats and multi-storey properties where impact noise transmission to the room below is a real consideration, sometimes even a building regulation requirement. Thickness on its own isn't a reliable guide to performance — a thinner rubber or dense foam underlay can outperform a thicker but less dense one, so it's worth checking the stated dB rating rather than judging by feel.
If the floor above will sit over underfloor heating, this needs a specific underlay rated for it — standard foam or rubber underlay can insulate against the heat rather than letting it transfer through, which defeats the point of underfloor heating entirely.
Matching Adhesive to Floor Type
Wood flooring adhesives aren't interchangeable with general building adhesives, and the type matters as much as the brand. Silane-based (SMP) adhesives, such as STAUF SMP 930 or Bona's silane range, are flexible once cured, low odour, and generally safe over underfloor heating — they're the common choice for solid and engineered wood boards laid as a full-spread bond. PVA adhesives are typically used for tongue-and-groove jointing rather than full-spread bonding — gluing the joints between boards rather than sticking the whole board to the subfloor.
Multi-purpose products like Everbuild Stixall sit outside the flooring-specific adhesives — they're general building adhesive-sealants, useful for trims, thresholds and fixtures rather than the main flooring bond itself. Using a general-purpose adhesive where a floor needs a specific flexible wood flooring adhesive can lead to boards cracking or lifting, particularly over underfloor heating where the subfloor expands and contracts.
Damp Proofing and Primers
Primers and damp-proof treatments aren't always optional, but they're also not universal — different products serve different purposes. Primers & treatments like Wakol D 3055 strengthen a porous or absorbent subfloor, such as calcium sulphate screed, so an adhesive bonds properly — but it isn't a moisture barrier on its own. A dedicated DPM primer, like Wakol PU 280, is applied specifically to block rising moisture from a concrete subfloor before flooring goes down, and is usually applied in two coats for full protection.
Skipping this step on a subfloor with any damp risk is one of the most common causes of flooring failure — the moisture doesn't disappear, it just ends up under the new floor instead.
Floor Fitting Kits
For straightforward jobs, fitting kits bundle the essentials — spacers, pull bars, tapping blocks and similar tools — so there's no need to source each item separately for a single installation.
Common Questions About Floor Fitting Supplies
Do I need underlay with a built-in damp proof membrane?
On a concrete ground-floor subfloor, yes — moisture can rise through concrete even when it looks and feels dry. On a suspended timber subfloor or an upper floor, a DPM is less critical, though acoustic underlay is often still worthwhile for noise reduction.
What's the difference between a primer and a damp proof membrane?
A primer strengthens a porous subfloor so adhesive bonds properly to it — it doesn't stop moisture. A DPM primer is a specific product designed to block rising moisture from the subfloor and is a separate, additional step where damp is a risk.
Can I use a standard PVA adhesive to fit an engineered wood floor?
PVA adhesives are generally used for gluing tongue-and-groove joints between boards rather than bonding the whole floor to the subfloor. A full-spread engineered or solid wood installation usually needs a flexible wood flooring adhesive, such as a silane-based (SMP) product.
Does my underlay need to be rated for underfloor heating?
Yes, if the floor will sit over underfloor heating. Standard underlay can insulate against the heat rather than letting it pass through into the room, so a specific underfloor-heating-rated underlay is needed to avoid reducing the heating's effectiveness.
