Planning
Subfloor Preparation: The Step That Decides How Long Your Floor Lasts
The most common flooring failure in Malaysian homes is not the plank — it is what the plank was laid on. Here is what a proper subfloor check involves, and why it is never a corner worth cutting.
Written by Renovix Home Services · Published
The short answer
Do I need to prepare the subfloor before installing new flooring?
Almost always, yes — and how much preparation depends on what is already there. A flat, dry, sound concrete screed or existing tile floor can often take new SPC, vinyl or laminate directly. An uneven, damp, hollow or crumbling base cannot: the new floor will telegraph every bump, click when walked on, or trap moisture and swell later. Preparation ranges from cleaning and a level check, through self-levelling or screeding, to hacking off the old floor entirely. The honest rule is to assess the subfloor before choosing the floor, because preparation is the single biggest hidden variable in a flooring quotation.
Key points
- A floor is only as good as its base — uneven or damp subfloors show up later as hollow spots, lifting planks and swelling.
- Three checks decide everything: level, moisture, and whether the existing surface is sound.
- Many floating floors can be laid over existing flat tiles without hacking — saving time, dust and money.
- Levelling or screeding is the biggest hidden cost in flooring; it is quoted after the base is assessed.
- If the old floor is hollow, cracked or water-damaged, hacking it off and preparing properly is cheaper than replacing the new floor twice.
What the subfloor is, and why it decides everything
The subfloor is the surface your new floor sits on: usually the concrete slab, a cement screed laid over it, or the existing floor you are replacing. A floating floor such as SPC, vinyl or laminate is not glued down everywhere — it locks together and rests on the base, which means the base is doing the structural work. If the base moves, hollows or holds moisture, the finish on top will show it.
- Concrete slab or screed: the most common base. Check it is flat, dry and free of loose, dusty or crumbling patches.
- Existing tiles: often fine to lay over, provided they are well bonded, not hollow and the extra height works for doors and thresholds.
- Old timber or parquet: must be checked for rot and bounce, and usually removed rather than covered.
- Newly screeded areas: need the correct curing time before anything is laid on top — moisture trapped under a floor is a warranty-ending mistake.
The three checks before any board goes down
Check the level
A long straightedge is run across the floor in both directions to find hollows and high spots. A floating floor tolerates a small tolerance; beyond that, the boards flex and the locking joints open up.
Check the moisture
This matters most on ground floors and anywhere a pipe or a bathroom is nearby. A damp base shows itself as a musty smell, staining or a hollow-sounding tile; trapping that moisture under new flooring is how swelling and lifting start.
Check the soundness
Tiles are tapped to find hollows, and loose or crumbling material is marked. Anything that moves or crumbles must be made good before the new floor goes over it.
How an uneven or failing base is made ready
The fix depends on what the checks find. Small local defects are patched; a generally uneven base is levelled; a badly failing one is hacked off and re-prepared. These are the published starting rates for the flooring work involved — preparation is quoted against the condition actually found on site.
| Old Floor Hacking & RemovalHacking and removal of existing tiles or flooring with disposal. | RM2per sqft |
|---|---|
| SPC Flooring InstallationSupply and install SPC (stone polymer composite) flooring with click-lock system and pre-attached underlay. | RM5.50per sqft |
| Vinyl Flooring InstallationSupply and install LVT vinyl flooring, suitable for bedrooms and living areas. | RM4.70per sqft |
| Laminate FlooringSupply and install laminate flooring for residential use. | RM6per sqft |
Subfloor levelling and screeding is quoted on top of the installation rate and depends on the condition found.
Rates below come from our published price list and are starting prices — the final quotation depends on the actual site condition and scope.
Prices start from the stated amount. Final quotation depends on actual site condition, scope, materials, accessibility and installation requirements.
Matching the preparation to the floor
| Flooring | What it needs under it | What it cannot hide |
|---|---|---|
| SPC | A clean, flat, dry base; tolerates minor unevenness well but not movement | A hollow or crumbling base — clicks and movement transmit straight through |
| Vinyl (LVT) | The smoothest base of the lot; imperfections show through thin planks | Roughness and dips — vinyl reads every bump underfoot |
| Laminate | Flat and dry above all else; its wood-fibre core swells with moisture | Damp or uneven ground — swelling and peaked joints follow |
| Parquet / timber | A fully sound, level base, usually glue or nail fixed | A moving or damp base — boards cup, lift and creak |
Whichever floor you choose, the sequence is the same: assess first, prepare second, install third. Reversing it is how a cheap installation becomes an expensive re-do.
When to leave it to someone who can see the problem
- The floor is visibly uneven, sloping, or has a high spot you can feel.
- Tiles sound hollow over a wide area, or some already move underfoot.
- There is a damp smell, staining or a history of leaks under or beside the floor.
- You are laying flooring over a bathroom, kitchen or ground-floor slab with no visible damp-proofing.
- The old floor is swollen, lifting or water-damaged and you are not sure what is underneath.
We assess the base before recommending anything, because the right preparation is what makes the difference between a floor that lasts and one that fails in its first rainy season.
Tell us the room, the condition of the current floor and whether you have ever had leaks or damp there. We will assess the base and tell you honestly how much preparation it needs before a single plank is ordered.
FAQs
Questions people ask about this
Can I lay new flooring over my existing tiles without hacking?+
In many cases yes, if the tiles are flat, well bonded and not hollow, and if the extra finished height works for your doors and thresholds. The base is checked first — where the tiles are uneven or failing, they come off or are levelled before the new floor goes down.
How long should new screed dry before flooring is laid?+
Long enough for the moisture content to fall to the level the flooring manufacturer specifies — and no fixed number of days substitutes for a moisture check. Laying a wood-based floor over a base that is still drying traps moisture and leads to swelling later.
Why do two similar homes get different flooring quotes?+
Because preparation differs. One base may be flat and dry and ready to lay on, while the other needs hacking, levelling or screeding. The material and installation rate may be identical; the preparation is what changes the total.
My floor sounds hollow when I walk on it. Is that a subfloor problem?+
Usually yes — hollow sounds point to a void or loose material underneath the finish, such as a debonded tile or a gap under the floating floor. It is worth checking before anything new is laid, because a new floor over a hollow base repeats the same sound.
What does subfloor levelling actually involve?+
The high and low points are mapped, and the base is brought flat — usually with a self-levelling compound or a fresh screed, depending on how far out it is. The area is then allowed to set before installation, so the finished floor sits level and does not flex.