Hacking Walls and Slabs in Singapore: Structural Elements, PT Slabs and Household Shelters

“Hacking” is Singapore construction shorthand for breaking out concrete or masonry: demolishing a wall, opening a doorway, chasing a wall for conduits, coring a slab for a pipe. It is also the most irreversible thing that happens in a renovation. A wrong partition can be taken down in a day; a wrongly cut beam, column, transfer element or post-tensioning tendon can compromise floors you do not own and people you will never meet.

Singapore regulates hacking in three overlapping ways. The Building and Construction Authority (BCA) decides whether the work needs structural plans and a permit, and its exemption list is drawn tightly around elements that carry no load. The Singapore Civil Defence Force (SCDF) and the Civil Defence Shelter Act protect household and storey shelters, which are deliberately strengthened and are not yours to weaken. And the Management Corporation Strata Title (MCST) or landlord controls what happens to the shared structure of the building.

This guide explains how to tell structural from non-structural elements, what you may do without a BCA submission (the list changed on 1 April 2025), when a Professional Engineer (PE) and a BCA permit are required, why post-tensioned slabs need special care, what the shelter rules allow, and what happens when it goes wrong. It complements our master guide on which approvals A&A and fit-out works need.

Structural or not: the legal test

The Building Control Regulations define a non-load-bearing wall (or vertical panel) as one that “supports no load other than its own weight”, and a partition as a non-load-bearing wall or panel used to subdivide space within a building.¹ That definition is the hinge for everything that follows: if a wall carries anything else — a slab, a beam, the wall above, lateral forces such as wind — it is not non-load-bearing, and the exemptions for wall demolition and wall openings do not apply.

The trouble is that the test is about what the wall does, not what it looks like. A brick wall can be load-bearing in an older building; a concrete wall can be non-structural infill; a thin wall can be a shear wall that keeps the whole frame stable. That is why the answer must come from the structural design, not from the contractor’s experience of “similar flats”.

Common structural elements and what they do

The table is a guide to conversation with an engineer, not a diagnostic tool. Ground floors of older buildings, transfer levels in podium blocks, and any building that has already had A&A works are where assumptions fail most often.

Where the evidence comes from

• Approved structural drawings. For most buildings, approved plans exist and can be purchased from BCA; BCA’s page on works not requiring approval links to its plan purchase application.³ For a strata unit, the MCST or managing agent may hold copies.
• A PE’s site inspection. The engineer compares the drawings with what is on site, notes past alterations, and decides what further investigation is needed.
• Non-destructive scanning and investigative openings. Used to locate reinforcement, tendons and services where the drawings are absent, unclear or doubted.

What you may do without a BCA submission

BCA calls works that need no plan submission insignificant building works, and they are exactly the items listed in the First Schedule of the Building Control Regulations.³ The list was expanded for works carried out on or after 1 April 2025.² For hacking and openings, the relevant items are:

Source: First Schedule, as currently in force.¹ Item 15 is new from 1 April 2025.²

Three practical cautions follow from the wording.

First, item 15 is for building services openings — pipes, conduits, cable trays — not for new staircases, hatches or ducts of any size. Second, the 450 mm spacing rule means that a cluster of small cores can fall outside the exemption even if each one is under 150 mm. Third, the exclusion of flat slabs and prestressed elements matters a great deal in modern commercial buildings, where long-span flat slabs and post-tensioning are common. If you do not know whether your slab is post-tensioned, you do not yet know whether item 15 applies.

Exemption from BCA submission is not exemption from everything else. BCA reminds owners that insignificant works must still be safe and comply with other agencies’ requirements, caveats and MCST by-laws.³ A cored hole through a compartment floor still needs fire-stopping under the Fire Code,¹⁸ and new openings in walls can change SCDF’s view of compartments and exits.¹⁷

When you need a PE and a BCA permit

If the work affects a structural element — opening a doorway in an RC wall, cutting or removing a beam, forming a larger slab opening, removing a column, adding a mezzanine, or strengthening — it needs structural plan approval and a permit to carry out structural works before work starts.⁴⁵

• Who submits. Only a Qualified Person who is a PE in the civil or structural discipline can apply for structural plan approval.⁴
• A&A that does not affect stability. Where the building’s structural stability or integrity is not affected, BCA asks for PE-endorsed plans with a certificate in the form of its Appendix D.⁴
• A&A that materially affects key elements. Where the works materially affect key structural elements (strengthening is BCA’s example), an Accredited Checker’s certificate is required.⁴
• Processing times. Within 7 working days of a complete submission without AC certification; 10 days (first submission) or 14 working days (subsequent) with AC certification; 20 working days for joint submissions in CORENET X’s Construction Gateway.⁴
• The permit. Applied for jointly by the developer, the QP and the builder, with or after plan approval, and processed within 7 working days of complete documents.⁵
• The builder. Building works whose plans need BCA approval must be carried out by a BCA-licensed builder; in-situ post-tensioning is one of the specialist builder categories.¹⁵

Changes during construction matter too. BCA requires approval before material changes that require redesign of key structural elements; immaterial changes can proceed but must be recorded in later plans.⁴ In practice, this means the “while we’re at it, can we widen that opening?” conversation on site needs to go back to the PE before anyone picks up a breaker.

Post-tensioned slabs: the special case

Post-tensioning (PT) puts high-strength steel tendons through a concrete slab or beam and stresses them after the concrete hardens, so the concrete is held in compression. It allows longer spans and thinner slabs, which is why it is common in offices, car parks and industrial buildings.

The structural logic that makes PT efficient is also what makes it unforgiving. A tendon is a stressed element. If a core bit or saw cuts it, the stored force is released and the prestress it provided is lost. In unbonded systems, where tendons sit in greased sheathing rather than grouted ducts, the effect is not confined to the point of the cut. STRUCTURE magazine’s guidance on PT repair is blunt that a cut or failed strand needs professional evaluation and “cannot be left cut or un-tensioned” just because the slab shows no visible distress, and that original plans and shop drawings may not match actual tendon placement, so locations should be confirmed by investigation such as ground-penetrating radar.¹³

Singapore’s regulations reflect this risk. The new slab-opening exemption in item 15 expressly excludes prestressed elements and flat slabs, and the forming of openings in those elements remains a matter for a PE and BCA.¹ Repair of a cut tendon (splicing and re-stressing, or new anchorages) is itself specialist structural work.

Coring and drilling: what else is in the concrete

Even where the slab or wall is conventionally reinforced and the opening is within the exemption, coring carries risks beyond the structure itself.

Scanning methods compared

Scanning is the main tool for reducing the risk of hitting something you cannot see. Each method has limits, and none replaces the drawings and a PE’s decision.

Scan results should be marked on the surface and recorded on a drawing that the PE accepts before coring, and the cored position should be checked against the marking before the bit goes in.

Household and storey shelters

What they are and why the rules are strict

Household shelters (HS) in homes and storey shelters (SS) in residential blocks are civil defence shelters designed to protect occupants in a war emergency. Their provision and technical requirements are regulated under the Civil Defence Shelter Act, which SCDF and BCA co-regulate: BCA approves shelter plans and commissions shelters, while SCDF processes waivers and conducts operational readiness inspections.¹⁰¹¹

SCDF’s guidance to owners explains the physical reason behind the rules: the shelter has strengthened walls, floor, ceiling and a specially designed door, which “must not be hacked or drilled”, and any repair, alteration or renovation likely to weaken or damage the shelter’s structural elements is not permitted.⁸

The legal rule

Section 4(1)(c) of the Civil Defence Shelter Act prohibits the owner or occupier from carrying out, or permitting, any repair, alteration or other work in a household or storey shelter that is likely to impair its efficient use, unless the Commissioner gives written permission. Owners must also maintain the shelter in accordance with the regulations and the Commissioner’s directions.⁹ Contravention carries a fine of up to S$5,000 and up to S$250 for each day the offence continues.⁹ Changing the use of any part of a building consisting of a shelter needs the Commissioner’s prior written approval.⁹

For landed homes with an existing household shelter, BCA requires the architectural and structural plans for the shelter to be submitted for approval when the house undergoes addition, alteration or reconstruction works, followed by a commissioning application on completion.¹⁰

What SCDF permits and prohibits

Source: SCDF, “Permitted and not permitted works for household shelters”.⁸

Notes for condominiums and non-residential buildings

In condominiums, storey shelters are typically on common property, so the MCST controls any work near them as well as SCDF’s rules. In non-residential projects, shelters are less common: BCA lists categories of buildings exempt from shelter provision, such as hotels registered under the Hotel Act, serviced apartments, dormitories and certain hostels and homes.¹⁰ Where a mixed-use or residential component has shelters, the fit-out team should mark them on the drawings as no-go zones for hacking and fixings.

Condominiums: by-laws and MCST approval

Strata developments add a private layer of control. BCA’s strata management guide sets out the framework.¹²

• By-laws on works in a lot (BMSMA s 32). MCSTs may make by-laws requiring subsidiary proprietors to meet requirements and obtain MCST approval before works, including PE endorsement of structural works and approvals from URA, SCDF and the Commissioner of Building Control.
• Works affecting appearance or structural integrity (s 37(4)). The owner must obtain the MCST’s authorisation before such works.
• Works affecting gross floor area (s 37). These need the MCST’s authorisation through a 90% resolution at a general meeting.
• Use of common property (s 33). Where works use common property, such as anchoring to an external wall, MCST approval (and possibly an exclusive use by-law) is required.

Structural walls, columns, beams and slabs in a strata development are usually common property even when they sit inside a unit, which is why MCSTs often insist on a PE’s endorsement before any hacking.

Two other landlords’ regimes are worth noting. In JTC buildings, tenants need JTC’s plan consent for A&A works, and for newly erected partitions JTC asks for the partition’s deadweight, thickness and height together with a PE (civil) endorsement, because even a non-structural wall adds load to a slab that was designed for a particular use.²⁰ In landed houses, URA’s exemption from planning permission for internal partitions applies only where the partitions do not change the house’s use as a single dwelling unit; creating a sub-dwelling unit needs a planning submission.¹⁶

Mezzanines, platforms and racking

Adding a mezzanine or raised platform is the reverse of hacking — it adds structure — but it raises the same questions. In industrial buildings, a single-level storage platform not accessible to the public, up to 4 m high and 50 m², with spans of up to 6 m and cantilevers up to 3 m, is an insignificant building work.¹ Beyond that, it needs BCA plans (or BCA’s lodgment route for qualifying platforms) and a permit. SCDF separately treats racking, platforms and mezzanines accessible by occupants as a floor or storey under the Fire Code, so they need fire safety plan approval before installation.²¹

Consequences when it goes wrong

The consequences come in layers.

1. Safety. Cracking, deflection, punching around columns, or sudden failure; in PT slabs, damage that may not be visible immediately.
2. Stop-work and propping. The building owner, MCST or regulator can require the area to be closed and propped until a PE has assessed it.
3. Regulatory exposure. Section 20 of the Building Control Act for unapproved structural works, with fines up to S$200,000 and daily fines for continuing contraventions;⁶ a pecuniary penalty under section 21 of up to 10 times the plan fees;⁷ and for shelters, the Civil Defence Shelter Act.⁹
4. Remediation. Investigation, structural design, strengthening or reinstatement, and regularisation submissions, all under time pressure. Our guide to regularising unauthorised works explains the route.
5. Commercial fallout. Landlord claims, neighbouring occupiers’ losses, delay to opening, insurer questions, and difficulties at handback or sale.

Key takeaways

The legal line is simple: only walls that carry nothing but their own weight can be removed or opened without BCA involvement, and only small services openings in ordinary slabs can be cored without a submission. Everything else needs a PE and a permit before work starts. Post-tensioned and flat slabs are outside the coring exemption entirely. Household and storey shelters are protected by statute and should be treated as untouchable apart from the narrow list of permitted finishes and fixings. For the wider approvals picture, return to the A&A approvals master guide, check fire implications in SCDF fire safety for fit-outs, or use the Approval Navigator to map your own works.