A&A can be a useful way to adapt a landed house when the existing building supports the functions you need. It is not automatically the simplest route merely because some walls will remain. Decide what must be retained for practical, planning or personal reasons, and what that retention demands of the design and construction.
Begin with a professional feasibility appointment before seeking a fixed construction price. Give the team the available records, access to the property and a ranked household brief. Ask for checked assumptions, unresolved questions and realistic alternatives.
This guide explains how to commission and compare that work. Planning, structural and site-specific decisions belong with the appropriate appointed professionals; the tables below help you ask a concrete question and recognise an incomplete answer.
Decide what the house must deliver
Write the brief in terms of use: an entrance-level bedroom, a kitchen that accommodates two cooks, a quieter workroom or a route suitable for someone with reduced mobility. State which outcomes are essential and which are preferences. This creates a meaningful comparison between an internal replan, an extension and a more extensive project.
Ask the designer to show the consequence of keeping important parts of the building. A retained stair may preserve character but constrain circulation. Keeping a roof may reduce one work package while limiting the intended room arrangement. An option deserves consideration because it meets the brief under checked constraints, not because it carries the A&A label.
Scroll across to compare all columns →
| Option | When to investigate it | Tradeoff to make explicit |
|---|---|---|
| Internal replan | The necessary functions may fit within the existing envelope. | Structural openings and services changes can still require professional review. |
| Targeted extension or alteration | A particular missing function cannot fit internally. | The new work must connect to retained structure, weather protection and services. |
| More extensive reconstruction | Several essential functions depend on major changes. | A different planning classification, scope and project commitment may apply. |
Buy evidence before certainty
Collect approved planning, building and structural records, current condition information and relevant land and services records. Ask the professionals to identify discrepancies and inspection limits. An old drawing or a visually tidy room cannot establish the condition of concealed work.
If you are assessing a purchase, identify the assumptions that could change the buying decision. Commission those enquiries first. A nice-to-have extension should not consume the whole review while the only possible entrance-level bathroom remains untested.
Sources: Building and Construction Authority: Building works not requiring approval · PUB, Singapore's National Water Agency: PUB Services Plans
- Pre-purchase A&A feasibility file
A records matrix and a worked purchase-decision exercise.
Separate planning classification from structural readiness
URA’s landed-housing A&A criteria consider several aspects of the proposal. In particular, adding a storey is treated as reconstruction. Ask the planning QP to establish the classification and applicable site controls; one percentage or the contractor’s project description cannot decide the route.
For structural work requiring approval, BCA identifies structural-plan approval and the permit as distinct steps. Have the appointed QP confirm the requirements and readiness of each proposed phase. The builder’s programme should reflect outstanding decisions rather than treating a hoped-for start as an approved one.
Sources: Urban Redevelopment Authority: Additions and Alterations to Landed Housing · Building and Construction Authority: Structural Plan submission
Make the retained-building scope comparable
Issue the same current drawings and assumptions to the teams you are comparing. Ask each to mark what is included, excluded or conditional. Separate investigation, design and authority work, construction, temporary protection, reinstatement and handover documentation so omissions are visible.
At the joins between old and new, name the party responsible for design, installation and inspection. A roof-to-wall junction, new drain connection or floor transition must be included somewhere even when several trades share it.
| Question | Useful answer |
|---|---|
| What is retained? | A marked plan and the condition assumptions behind retaining it. |
| What remains unknown? | The missing fact, proposed investigation and effect if the assumption fails. |
| Who completes the interface? | Named responsibility tied to a drawing or written detail. |
| How will a change be agreed? | Evidence, alternatives, price and programme effect before approval. |
Plan the work around its surroundings
Discuss nearby buildings, access, deliveries and protection with the engineer and builder early. A neighbour’s permission to inspect is not the same as permission to use their land for construction. Requests should identify the actual task, duration, protection and reinstatement proposed.
BCA and URA’s advisory neighbour guide recommends recording nearby property conditions for piling or excavation. Use a defined report scope and contact process, with professional assessment kept separate from household observations. A baseline photograph alone cannot decide the cause of later damage.
Choose an occupation plan you can actually use
Assess staying at home by construction phase. Trace how the household will enter, sleep, wash, prepare food and remain separated from work. A spare room cannot solve a lost staircase route or a major services interruption.
Agree relocation triggers and allow for temporary accommodation, storage and repeated moves when comparing options. Ask how the programme changes if investigations reveal that the proposed occupied arrangement cannot continue.
Turn the preferred proposal into an agreement
Use a written scope, programme and payment arrangement that correspond to the same design. Clarify conditional amounts and how they will be adjusted. A homeowner’s contingency budget does not automatically authorise additional contractor work.
CCS renovation guidance recommends transparent pricing, clear descriptions and express agreement for changes. Apply those principles to the actual project: each change should explain what prompted it, which option was accepted and how the cost and schedule change. Have the appropriate adviser review contractual questions that matter to your appointment.
Keep a record useful for the next alteration
Agree the handover documents before work begins. Depending on the scope, these can include final drawings, relevant approvals and completion documents, services information, product details, warranties, inspection or test records and an outstanding-work list. Ask the QP and builder to define which records apply.
Store the information by building system and location. Future maintenance is easier when the next team can establish where the new work meets the old, what was concealed and which limitations remain. Retain the final scope and change record with the drawings.
Sources and scope
Our editorial team checked the references below. Manufacturer guidance applies to the products and arrangements it describes; confirm the documents for your proposed installation.
- Building works not requiring approval
Building and Construction Authority · Checked
BCA's buyer guidance recommends professional inspection against approved plans and explains the limits of a legal search.
- PUB Services Plans
PUB, Singapore's National Water Agency · Checked
Services-plan coverage, omissions and QP site-verification requirements before design.
- Additions and Alterations to Landed Housing
Urban Redevelopment Authority · Checked
Planning A&A criteria, additional-storey reconstruction classification and conditional retention of previously approved non-conforming structures.
- Structural Plan submission
Building and Construction Authority · Checked
Structural-plan applicant qualifications, permit process and additional certification considerations for A&A.
- Be Good Neighbours, amended October 2025
Building and Construction Authority and Urban Redevelopment Authority · Checked
Advisory guidance for landed-house works: neighbour engagement, surveys, excavation impacts, party-wall and roof interfaces.
- Guide on Fair Trading Practices for Renovation Industry
Competition and Consumer Commission of Singapore · Checked
Consumer guidance on clear scope, price, timelines, changes and agreed remedies.
Regulatory compliance
Check which requirements apply to your proposed scope. Agree the responsible qualified professionals, submissions and inspections before work begins.
URA (Urban Redevelopment Authority)
The planning QP establishes the applicable landed-housing classification and development controls.
Primary source: www.ura.gov.sg/guidelines/development-control/development-control-handbooks/residential/bungalows/aa-landed-housingBCA (Building and Construction Authority)
The structural QP establishes the relevant structural assessment, submission and permit requirements.
Primary source: www1.bca.gov.sg/safety-and-standards/applications-and-licenses/structural-plan-submissionGlossary
- A&A
- Additions and alterations; the planning classification depends on the actual proposal, not merely the project name.
- Interface
- The junction or shared responsibility where new work connects to retained structure, finishes or services.
- Conditional allowance
- An amount or scope assumption that needs a clearly agreed basis for adjustment when information becomes available.
Frequently asked questions
Is A&A always cheaper than reconstruction?
Not necessarily. Compare defined options that deliver the same essential functions, including retained-building investigations, temporary works and interface work. An overall label does not establish the total scope.
Can the contractor decide that no submission is needed?
Ask the appropriate appointed QP to establish the route for the actual works. Keep their advice and the relevant references with the project documents.
What should I send before the first meeting?
The property address and type, available drawings, photos taken safely, access arrangements, essential household outcomes and the decisions you need the feasibility review to resolve.
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Go deeper: a&a works articles
In-depth pieces that expand on the sections above: real costs, brand and system comparisons, the installation process, and the edge cases most homeowners hit.
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A&A Plans Approved: Can Structural Work Start?
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Before Buying a Landed House to Renovate: The A&A Feasibility File
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