Who this guide is for
- Homeowners planning a single or two-storey extension
- People who want the extension to suit the existing house
- Anyone needing approvals coordinated
- Owners comparing architects for an extension
Judge massing and connection to the house
A good extension is the right size and shape and connects naturally to the original house, inside and out. Ask how the architect approaches massing and the junction with the existing building, and look at extensions they have designed.
Extensions that fight the original house rarely satisfy.
- Ask how massing is approached
- Discuss the connection to the existing house
- View past extensions
- Look at how old and new meet
Understand approvals coordination
Extensions usually involve approvals, and a key part of an architect's value is guiding that process. Ask how they coordinate approvals and inspections, while remembering this is their and the authority's domain, not yours to assume.
Do not start work assuming approval is not needed.
- Ask how approvals are coordinated
- Treat approval as the professional's domain
- Do not assume approval is unnecessary
- Confirm who handles submissions
Think about services and structure
Extensions affect heating, electrics, drainage and structure, and these have to be designed in, not bolted on. Ask how the architect handles services and coordinates structural input.
Keep structural design with qualified engineers.
Confirm the architect's scope and stages
Architects work in stages, from concept through to detail and sometimes site oversight. Be clear which stages you are engaging them for and what each includes.
Match the scope to how much support you want.
- Clarify which stages you are engaging
- Confirm what each stage includes
- Match scope to the support you want
- Discuss site involvement
Brief and compare clearly
Give each architect the same brief and picture of your house so proposals compare. Ask about extensions like yours and confirm fees in words and relevant registration.
Keep technical and approval matters with the right professionals.
Hiring checklist
- 1Define what the extension must achieve
- 2Ask how massing and connection are approached
- 3View past extensions like yours
- 4Ask how approvals are coordinated
- 5Discuss how services are handled
- 6Confirm structural input is coordinated
- 7Clarify which design stages you are engaging
- 8Confirm what each stage includes
- 9Give each architect the same brief
- 10Confirm fees in words and relevant registration
Common mistakes to avoid
- Focusing only on the new room, not how it joins the house
- Assuming approvals are not needed for an extension
- Treating services and structure as afterthoughts
- Engaging unclear design stages and scope
- Comparing proposals that are not like for like
- Overlooking the architect's relevant experience
When to involve a professional
- Treat approvals and inspections as the architect's and authority's domain
- Keep structural design with qualified engineers
- Ask to see comparable extensions before engaging
- Confirm relevant registration and insurance
- Remember approval and structural requirements vary by location and project
Frequently asked questions
Questions readers ask about this topic
Why hire an architect for an extension?
An extension must add space while respecting how the existing house looks and works, including massing, the connection to the original building and services. An architect handles these and coordinates approvals, which is where their value shows on an extension.
Who handles approvals?
Extensions usually involve approvals, and guiding that process is part of an architect's value, but it is their and the authority's domain, not something to assume either way. Ask how they coordinate approvals and inspections.
What about structure and services?
Extensions affect heating, electrics, drainage and structure, which must be designed in rather than bolted on. Ask how the architect handles services, and keep structural design with qualified engineers, since requirements vary by location and project.
What design stages do I need?
Architects work in stages, from concept through to detail and sometimes site oversight, so be clear which you are engaging them for. Confirm what each stage includes and match the scope to how much support you want.
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