Your contractor will almost certainly recommend hacking your existing tiles. It's more work, which means more money for them. Overlay is often equally viable and saves you $3,000–$6,000. Here's how to tell which option is actually right for your situation.
What Overlay Actually Is
Tile overlay means installing new tiles directly on top of existing tiles, using a modified tile adhesive designed to bond to existing tile surfaces. The existing tiles stay in place and new tiles go on top.
- Durability: Done correctly by a competent tiler, overlay produces a floor that's just as durable as a hacked-and-retiled floor and is typically indistinguishable in appearance.
- Risks: Done incorrectly — with the wrong adhesive, insufficient preparation, or tiles that are already compromised — overlay can lead to delamination and popping tiles later.
When Overlay Is Appropriate
Overlay works well when:
- The existing tiles are solid: Test by tapping across the floor with a coin or marble. A ringing sound indicates the tile is well-adhered; a hollow thud indicates a tile that has lost adhesion. If more than 20–30% of tiles are hollow, hacking is the better choice.
- The floor is level: Adding a layer of tiles raises the floor height by 10–14mm. If your existing floor has significant unevenness, overlay won't correct them — it will follow the existing contour.
- Acceptable height differential: The new floor level must transition appropriately to adjacent rooms and fixed elements. If it creates a trip hazard, hacking may be preferable.
- HDB permits it: HDB generally permits one layer of tile overlay. Overlaying a second time is typically not permitted due to structural load concerns.
When Hacking Is Necessary
Hack the existing tiles when:
- Significant tile hollow exists (30%+ of tiles are hollow or popping).
- The floor is visibly uneven and re-screeding is needed.
- You're installing vinyl flooring, which requires a very flat and smooth substrate.
- The existing tiles are very thick and the overlay would create problematic height differentials.
- You're converting a tiled area to a timber or vinyl finish that requires bonding directly to screed.
The Honest Cost Comparison
For a 4-room HDB main living area (roughly 40–50 sqm):
- Hacking: $6–$10 per sqm for demolition + $15–$25 per sqm disposal fees + screed repairs = $1,500–$2,500 before the new tiles even go down.
- Overlay: Tile adhesive and preparation costs instead of hacking — typically $800–$1,200 total premium over a direct new installation.
Note: On a $60,000 renovation, saving $1,500–$2,500 on flooring that doesn't need hacking is meaningful.
The Contractor Incentive You Should Know About
Hacking generates work volume and material handling fees. An unscrupulous contractor can add $3,000–$5,000 to a project by recommending hacking that isn't necessary. Many will default to "better to hack" without genuinely assessing whether overlay is viable.
What to do: When a contractor recommends hacking, ask them to show you specifically which tiles are hollow. If they can't point to specific tile failures or structural reasons, push back and ask for a proper assessment.
The Bottom Line
Check your existing tiles systematically with a tapping test. If they're solid, overlay is almost always viable and substantially cheaper. If they're significantly hollow or damaged, hacking is the right call. Don't let the default recommendation become your decision — make the contractor explain their reasoning.
