Why What’s Under Your Floors Matters Just as Much as the Flooring You Choose
When selecting new flooring, most people focus on what they can see — the colour, the finish, the texture, the way it complements the room.
But the visible surface is only half the story.
What sits beneath your flooring — the subfloor and the underlay — plays a decisive role in how that flooring performs, feels, and lasts. Without proper assessment and preparation, even premium products can fail prematurely. Boards separate. Floors creak. Movement appears. Warranties are compromised.
At AMS Flooring, we understand that long-term performance begins below the surface.
The Subfloor: The True Foundation of Your Flooring
Every floor covering relies on a stable, level, and structurally sound base. Whether the subfloor is concrete, timber, or an existing surface being overlaid, it must meet strict tolerances before installation begins.
Minor deviations in flatness can create major problems over time. A floor that looks perfect on day one can begin to shift, flex or separate simply because the substrate beneath it wasn’t properly prepared. Floating floors are especially sensitive to variation, but even direct-stick products rely heavily on correct preparation.
Subfloor preparation isn’t cosmetic — it’s structural. Grinding high spots, filling low areas, repairing cracks, stabilising timber movement, and applying moisture barriers where required are all precision tasks. They require proper assessment, not assumptions.
Skipping this stage is one of the most common causes of flooring failure.
Moisture: The Often Overlooked Risk
Moisture is one of the most damaging forces in flooring installation. Concrete slabs can retain moisture long after construction is complete, and timber substrates can be affected by seasonal changes in humidity.
Without proper moisture testing, installers are effectively guessing.
Excess moisture beneath flooring can lead to swelling, adhesive breakdown, mould growth, and irreversible structural damage. In many cases, problems do not appear immediately — they surface months later, when rectification is far more disruptive and expensive.
Professional moisture testing and mitigation are not optional extras. They are essential safeguards.
Underlay: More Than Just Padding
Underlay is often misunderstood as a comfort layer, but its function is far more technical.
The correct underlay influences acoustic performance, thermal insulation, shock absorption, moisture control, and overall stability. In floating floor systems, it directly affects how the floor responds to movement and load.
Choosing the wrong underlay can compromise the performance of even the highest-quality flooring product. It may cause excess movement, increase noise transfer, or void manufacturer warranties.
Compatibility matters. Underlay must be selected based on the flooring type, the subfloor condition, and the performance requirements of the space.
The Long-Term Cost of Overlooking What’s Beneath
When flooring fails, it is rarely because the product itself was defective. More often, the issue traces back to inadequate preparation or incorrect installation methods.
Rectifying subfloor issues after flooring has been installed typically involves removing the entire surface, correcting the substrate, and reinstalling new material. The cost — both financially and practically — is significantly higher than preparing it properly from the outset.
Investing in correct subfloor assessment and preparation protects not just your flooring, but your property.
Our Approach
At AMS Flooring, we approach every project with a technical mindset. Before installation begins, we assess flatness, moisture levels, structural integrity, and product compatibility. We ensure that the chosen flooring system is supported by the correct preparation and underlay.
Because flooring should not just look good — it should perform consistently for years.
The visible surface may define the aesthetic of a space. But the unseen foundation determines its longevity.
Subfloor and Underlay FAQ
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Most flooring manufacturers specify strict flatness tolerances, often within a few millimetres over a defined distance. If the subfloor falls outside these tolerances, it must be corrected before installation. Even small deviations can lead to movement, joint separation, or premature wear.
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Yes. Moisture is one of the most common causes of flooring failure. Concrete slabs and timber subfloors can retain moisture that isn’t visible to the eye. Professional testing ensures levels are within manufacturer guidelines and protects both the flooring and your warranty.
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In most floating floor systems, underlay is essential. It provides acoustic control, stability, shock absorption, and in some cases moisture protection. However, some hybrid products come with pre-attached underlay, so compatibility should always be confirmed before installation.
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In some cases, yes — but only if the existing surface is stable, level, and suitable as a substrate. Proper assessment is required to determine whether preparation, levelling, or removal is the better long-term solution.
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Improper preparation can lead to movement, creaking, lifting, visible deflection, adhesive failure, or warranty issues. Rectification often requires removing the flooring entirely, which is significantly more costly than preparing the subfloor correctly from the start.