Can underlay cause floors to feel soft?

Yes. Overly soft or incorrect underlay is a common cause of soft flooring underfoot.

Will soft spots get worse over time?

Often, yes. Continued movement can weaken joints, adhesives, and subfloor integrity.

Why Floors Feel Soft Underfoot After Installation?

You’ve just had brand-new floors put in, and instead of that lovely solid feeling underfoot, something’s… off. There’s a soft, spongy give when you walk across the room — a little bounce that definitely wasn’t in the brochure. If your stomach dropped a bit when you noticed it, that’s completely understandable. New floors are meant to feel rock-solid, so a soft spot naturally makes you worry something’s wrong underneath.

Here’s the good news, and we mean it: most of the time, a spongy floor is fixable, and it doesn’t automatically mean your whole floor is ruined. In this guide we’ll gently walk you through why it happens, how to work out the cause, what a repair typically costs, and exactly when it’s worth picking up the phone to your installer.

The short answer: a spongy or soft floor after installation is almost always caused by one of a few things — an uneven subfloor, the wrong or overly soft underlay, moisture trapped underneath, or patchy adhesive during a glue-down install. A tiny bit of flexibility can be perfectly normal, but softness that’s obvious, repeatable or getting worse should always be checked before it does any harm.

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For a closer look, see our guide to underlay for hybrid and laminate flooring.

What Causes a Spongy Floor After Installation? (The 6 Main Reasons)

Let’s demystify this. When a new floor feels soft, it’s nearly always one of these six culprits — and understanding which one you’re dealing with is the first step to fixing it.

An uneven or poorly prepared subfloor

This is the number-one cause, by a wide margin. If the surface underneath your floor has dips, humps or waves that weren’t smoothed out first, the boards on top are left “floating” over those gaps with nothing to support them. So when you step on that spot, the floor flexes down into the hollow — and you feel that tell-tale sponginess. It’s especially common in older Melbourne homes with timber subfloors, where levelling sometimes gets rushed or skipped.

The wrong underlay

Underlay is meant to support your floor, not act like a cushion. When it’s too thick or too soft for the flooring system, it squashes down under your weight instead of holding firm, leaving the whole floor feeling bouncy. It’s a really common trap — lots of people assume “thicker underlay = more comfort,” when in reality the wrong choice creates instability and stresses the joints over time.

Moisture in the subfloor

Water is a quiet troublemaker. Excess moisture weakens both the subfloor and the bond above it — timber swells and softens, and concrete slabs stop adhesives from curing properly. Either way, the floor loses its firm grip on the base and starts to move underfoot. This one shows up most often when moisture testing gets skipped before the install.

Poor adhesive coverage or fixing

In glued-down floors, if the adhesive was spread patchily, you end up with hollow pockets where the board simply isn’t stuck down. Walk across one of those and it feels noticeably different — softer, sometimes with a faint crackle. In floating floors, the same feeling comes from a gap in support or a joint that never fully clicked home.

A flexible or damaged subfloor structure

Sometimes the surface is perfectly level, but the structure beneath it still moves. This happens in older timber homes where the joists are spaced too far apart, have been weakened, or have shifted over the years. The whole floor gives slightly under load, and that movement travels straight up to your lovely new boards.

An incompatible flooring-and-subfloor combination

Not every floor suits every base. Lay a rigid flooring system over a flexible or poorly supported subfloor and it might look great on day one — but as everyday life happens on top of it, that mismatch starts to reveal itself as softness and movement.

Discover our top product categories: It also helps to understand floating vs glued flooring.

Spongy Floor by Flooring Type

The cause — and the fix — often depends on what you’ve actually got underfoot. Here’s how it tends to play out across the common floor types.

With laminate, the rigid planks are pretty unforgiving over dips, so sponginess almost always traces back to an uneven subfloor or an over-compressible underlay. Hybrid has a stiff, rigid core that resists flexing, which means if it feels soft, the subfloor itself is usually the one moving. On glue-down vinyl, softness points straight to hollow spots where the adhesive didn’t grab. With floating floors, a little give is normal — but repeatable soft spots suggest support gaps or an underlay issue. And engineered timber bounce most often comes from joist movement or a subfloor that wasn’t fixed down firmly enough.

How to Work Out the Cause Yourself

Before you call anyone, you can do a bit of friendly detective work — it’ll help you (and your installer) enormously.

Start by walking the room slowly and marking every spot that dips or feels bouncy with a bit of low-tack tape. Then look at the pattern: isolated soft spots usually mean subfloor voids or adhesive gaps, while a whole room that feels soft points more towards underlay or structural movement. Listen as you walk — a click or crackle alongside the softness suggests unlocked joints or hollow areas. Check for moisture clues like a musty smell, cupped boards or a nearby wet area. And finally, keep an eye on the timing: softness that’s slowly getting worse over the weeks is a genuine red flag, not just the floor settling in.

Installation Mistakes That Create Soft Spots

Most sponginess comes down to avoidable shortcuts during the install — and it helps to know what they are. Skipping proper subfloor levelling leaves those unsupported hollows. Not fixing or gluing the floor down firmly enough creates movement. Using an underlay that’s too soft or too thick lets the floor compress underfoot. And laying over a damaged or flexing subfloor without repairing it first bakes the problem in from the start. The frustrating part is that none of these usually show up to the eye — you only discover them the moment you walk across the room.

When a Soft Floor Is Normal, and When to Call a Professional

A little reassurance here: some minor flexibility can be completely normal, especially with floating floors laid over timber subfloors. It only becomes something to act on when the floor visibly dips as you step on it, the soft spots are localised and repeatable, there’s clicking or creaking along with the movement, or — the big one — it’s feeling worse over time rather than settling down. If the softness is spreading across the room or clearly getting worse, it’s crossed the line from “normal” to “get it checked.”

How to Fix a Spongy or Soft Floor (Step-by-Step)

The exact repair depends on the cause, but the overall process is reassuringly logical. Here’s how a proper fix usually unfolds.

Confirm the cause first. A proper inspection pinpoints whether it’s the subfloor, underlay, moisture or adhesive at fault — because fixing the wrong thing just wastes time and money.
Deal with any moisture before anything else. No repair will hold over a damp subfloor, so this always comes first.
Re-level the subfloor where it’s needed. On concrete, that’s usually a levelling compound; on timber, it might mean re-fixing or replacing sheeting to create a flat, solid base.
Bring back the support. For hollow glued areas, a specialist can inject a filler under the planks; for underlay or floating-floor issues, the affected sections are lifted and relaid with the correct materials.
Refit the flooring properly — with the right expansion gaps, the correct underlay and a firm fix — so the softness doesn’t simply return a few weeks later.

Cost to Fix a Spongy or Soft Floor in Melbourne

What you’ll pay depends entirely on the cause and how much floor is involved. A minor fix — re-fixing a small area, adding support under a hollow spot or clearing a blocked edge — is often just a call-out fee plus a little labour. Re-laying a section with the correct underlay sits higher, in the low-to-mid hundreds depending on the area. And where the real culprit is the subfloor — levelling a concrete slab or repairing timber sheeting and joists before relaying — the cost climbs with the size of the job. The encouraging news is the same as always: sorting a soft spot early is far cheaper than letting the movement spread and damage more of the floor. If you are comparing options, read about the best flooring for uneven subfloors.

Is a Spongy Floor Dangerous or a Structural Risk?

In most cases, a slightly soft or bouncy floor is a comfort-and-quality issue rather than a safety emergency — especially the gentle give you sometimes get with a floating floor over timber. It becomes something to take more seriously when the softness is spreading, the floor visibly dips underfoot, or it comes with a musty smell, cupped boards or movement in the structure below, since those can point to moisture damage or weakened joists. If in doubt, it’s worth having it checked: the vast majority of spongy floors are a straightforward fix, and a quick professional look tells you for certain whether it’s cosmetic or structural.

How to Prevent Soft Floors (Subfloor Prep & Acclimation)

Nearly every spongy floor traces back to something skipped before the boards went down, so prevention is mostly about getting the groundwork right. Start with a clean, level, dry subfloor — levelling compound on concrete, or re-fixing and reinforcing timber where needed. Choose the correct underlay for your flooring, firm and supportive rather than the softest option. Moisture-test the subfloor before laying, especially on slabs. Allow proper acclimation so the boards settle to your home’s conditions first. And make sure the floor is fixed or clicked home firmly with the right expansion gaps. Tick those off and sponginess rarely gets a chance to appear.

Who Is Responsible? Installer Warranty & Your Rights

If your floor turns spongy soon after a professional installation, this is often a workmanship issue — and many installers offer a workmanship warranty that covers exactly these post-installation problems, so it may well be a free fix. Under Australian Consumer Law, services also need to be carried out with due care and skill, which gives you a fair footing to ask for it to be put right. Get in touch with your installer promptly, describe what you’re feeling and where, and keep your invoice and any warranty paperwork handy. One important note: avoid a major DIY repair while the floor is still under warranty, as that can void your coverage — give the installer the first chance to make it good.

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FAQ

Why does my new floor feel soft and spongy underfoot?

Usually because of an uneven subfloor, an over-soft or wrong underlay, trapped moisture, or patchy adhesive during a glue-down install. A quick inspection pinpoints which one.

Is a spongy floor normal after installation?

A little give can be normal, especially with floating floors over timber. It’s worth checking when the softness is obvious, repeatable or getting worse over time.

Can I fix a spongy floor without removing it?

Sometimes — clearing a blocked expansion gap or injecting filler under a hollow glued area can work. But if the cause is the subfloor or underlay, the affected section usually needs lifting and relaying.

Does underlay thickness matter for a soft floor?

Yes. Underlay that’s too thick or too soft lets the floor compress and flex underfoot. A firm, supportive underlay matched to your flooring is what keeps it feeling solid.

How long before a new floor settles?

Minor settling usually eases within the first few weeks. Softness that persists or worsens beyond that isn’t just settling and should be inspected.

How much does it cost to fix a spongy floor?

Minor fixes are often just a call-out fee plus labour, relaying a section runs into the low-to-mid hundreds, and subfloor repairs cost more depending on the area involved.

Why Floors Feel Spongy or Soft Underfoot After Installation