What is Addition and Alteration (A&A) Works? A Complete Guide for Singapore Homeowners

Learn what A&A works are, what qualifies under BCA criteria, the approval process, typical costs, and when to choose A&A over a full rebuild.

What is Addition & Alteration (A&A) Works?

Addition & Alteration (A&A) works refer to modifications made to an existing building's structure or form without demolishing the entire building.

In simple terms, if you are extending your home, adding an attic, widening an opening, or changing the structural layout while retaining the existing building, it is generally considered A&A works.

This differs from a full demolish and rebuild, where the existing structure is completely torn down and a new building is constructed from scratch.

Criteria for a Project to be Considered A&A

Below are some common criteria for a project to qualify as A&A works. If the proposal exceeds these limits, it may instead be classified as reconstruction.

1. New Gross Floor Area (GFA) does not exceed 50% of the existing GFA

— Example: If the existing GFA is 2,000 sqft, the new GFA after A&A works cannot exceed 3,000 sqft

1. Structural changes do not exceed 50% of the existing building
2. Addition of an attic only, not an additional storey
3. Existing walls removed or replaced do not exceed 50% of the existing walls
4. The works do not result in a change of housing form

— Example: Changing from a semi-detached house to a detached house

What Falls Under A&A Works?

Common examples of A&A works for landed homes in Singapore include:

• Vertical extensions — adding an attic
• Horizontal extensions — extending rooms outward (subject to allowable setbacks and site coverage limits)
• Structural alterations — removing or relocating load-bearing walls, widening door or window openings
• Façade alterations — changing the external appearance, adding or removing windows, or altering the roof profile

Minor internal works — such as repainting, replacing flooring, or installing non-structural partition walls — are generally considered renovation works and typically do not require BCA approval.

Do I Need BCA Approval for A&A Works?

Yes. A&A works require approval from the Building and Construction Authority (BCA) under the Building Control Act.

The process generally involves:

1. Engaging a BCA-registered contractor and a Qualified Person (QP)
2. The QP prepares and submits plans to BCA through the CORENET e-submission system
3. Obtaining [URA Written Permission (WP)](https://www.ura.gov.sg) if the works affect the building's external appearance or footprint
4. Receiving Permit to Work (PTW) before construction can commence
5. Obtaining a Temporary Occupation Permit (TOP) or Certificate of Statutory Completion (CSC) upon completion

For a full walkthrough of each stage, see our step-by-step guide to the Singapore building permit process.

When is A&A Works Suitable?

A&A works are generally suitable when:

• The existing structure is in good condition
• The scope of changes is relatively targeted
• You wish to retain certain existing building features
• A full rebuild is not necessary

How Long Do A&A Works Take?

A typical A&A project timeline is as follows:

• Permit submission and approval: 2–4 months
• Construction: 2–8 months, depending on the scope of work

Total estimated timeline: approximately 4–12 months from engagement to completion.

How Much Do A&A Works Cost in Singapore?

The cost of A&A works varies depending on the scope, structural requirements, specifications, and finishes.

General Cost Guide

• Minor A&A works (internal reconfiguration, small extensions): SGD 80,000–200,000
• Major A&A works (attic addition, significant extensions, major structural works): SGD 200,000–800,000+

Conclusion

A&A works offer homeowners a practical way to upgrade and expand their landed property while retaining the existing structure.

However, the suitability of A&A depends on the structural condition of the house, the extent of the proposed changes, and regulatory requirements. Understanding the scope, approval process, and limitations early will help homeowners plan their projects more effectively and avoid unnecessary delays or costs.

Ming Sia Construction offers full rebuild and A&A services for landed homes across Singapore. Contact us for a site assessment and non-obligatory quotation for your project.