What You Can and Can't Hack in an HDB Flat (Permits, Wet Areas and Protected Elements)

The short version of the rules

Renovation works in an HDB flat are governed by HDB's published renovation guidelines, carried out only by an HDB-registered contractor who files the renovation permit before any work starts — and your own flat's structural drawings have the final say on what any given wall actually is.

Three layers sit behind every hacking decision. First, the permit: regulated works must be submitted by your registered contractor and approved before they begin. Second, the guidelines: HDB sets out what categories of work are permitted, restricted or prohibited. Third, the flat itself — two flats on the same floor can differ, so a wall you assume is a partition may be load-bearing on someone else's plan. This is why no responsible designer answers 'can I hack this wall?' from a photo: layout first, check the drawings, confirm the guidelines, then file the permit.

What generally CAN be hacked

Generally, and subject to your flat's drawings, non-structural internal walls can be hacked — the partitions that shape how a flat flows rather than how it stands up.

'Generally' is doing real work there. A kitchen mid-wall that opens the cooking area to the dining space is one of the most transformative hacks in a typical flat, precisely because it carries no load — but feasibility is verified per flat, against the drawings, before anything is priced or permitted.

It also helps to separate hacking from rebuilding: the demolition itself is often the cheapest line item, and the redesign around it is what earns the cost.

• Non-structural internal walls — typically kitchen mid-walls and some bedroom partitions, confirmed against your flat's structural plan first
• Floor and wall finishes — tiles, skirtings and surface finishes can generally be hacked and re-laid
• Carpentry-affected features — built-in wardrobes, kitchen cabinets and other carpentry-fixed items can generally be removed or repositioned

What must NOT be hacked

Structural walls, columns and beams, post-tensioned slabs where present, waterproofed bathroom floors, protected installations such as the household shelter and its door, and windows — which follow separate rules — must not be hacked.

The household shelter deserves special mention as the most underestimated restriction: every newer flat includes one, and it cannot be hacked, relocated or have its door altered — good design integrates it as fixed infrastructure rather than treating it as an obstacle.

None of this is negotiable through clever phrasing on the permit. Unauthorised hacking invites reinstatement orders and affects the building's safety — a contractor willing to skip the checks isn't protecting you, they're transferring the risk onto your title.

Wet areas and waterproofing

Bathroom floors are protected because they carry a waterproofing membrane beneath the tiles — hack through it, and the failure surfaces as a leak in your downstairs neighbour's ceiling, weeks after your renovation looked finished.

The membrane sits under the tiles doing quiet work for decades; hack the floor and it goes with them. Re-waterproofing done properly means stripping back, laying a new membrane, pond-testing it, then tiling over — which is why wet-area retiling is priced differently from living-area flooring, and why damage that emerges below traces back to whoever breached the membrane.

So our default is to overlay or retain sound bathroom floors rather than hack them. If falls, drainage and tile condition are acceptable, keeping the floor avoids both the risk entirely and a meaningful slice of budget. When a strip-out is genuinely needed, it becomes deliberate, properly detailed scope — not a casual line item.

The permit process in practice

Your registered contractor submits the renovation application to HDB before works begin; approval commonly comes through in about a week, and all works run within HDB's permitted hours.

In practice the permit is paperwork your contractor owns but you should understand. The submission declares the regulated works — hacking, tiling quantities, plumbing — and can't be filed until the scope is finalised, another reason late layout changes are expensive. Once approved, works run inside HDB's permitted time windows: general renovation within weekday and Saturday daytime hours, noisier works on weekdays only, nothing on Sundays and public holidays. Keep the approved permit accessible during works — checks do happen, and a compliant project has nothing to hide.

How we approach hacking decisions

We hack only when it earns its cost — when removing a wall genuinely improves light or layout logic — and we overlay or keep what already works, because the best hacking decision is often the one you don't make.

A hack passes our test when it changes how the flat lives: opening a boxed-in kitchen to daylight, joining a dead hallway to the dining zone. If the benefit is a slightly straighter wall or a trend, the dust isn't worth it. The same discipline applies in reverse — many resale flats need editing, not erasing, and overlaying floors or retaining a working bathroom costs less and carries less risk than wholesale hacking. We set both paths side by side, as we do in our article on hacking versus overlaying in resale flats.

Every proposal ends the same way: confirmed against your flat's structural drawings, checked against HDB's current renovation guidelines, permitted before works. That order protects the building, your neighbours and your ownership — and lets us design boldly everywhere else.