Key Takeaway
Compare extension design fee structures by checking the defined scope, exclusions and package deliverables.
How do project costs and planning routes compare?
Extensions add to the building, while loft and garage conversions work with existing space; each has different structural and planning considerations. The route depends on the property, so these comparisons are not an individual planning decision or quotation.
| Project | Typically needs planning? | Main cost factors | Typical design route |
|---|---|---|---|
| Single-storey extension | May qualify for permitted development if all conditions apply | Footprint, foundations and specification | Survey, layout, planning check and technical drawings |
| Two-storey extension | Depends on the design and permitted development limits | Structure, roof design and specification | Survey, planning check and coordinated structural information |
| Loft conversion | Some roof works may qualify, subject to restrictions | Roof type, stairs and structural work | Roof and layout assessment, planning check and Building Regulations |
| Garage conversion | Often possible without a planning application, but exceptions apply | Insulation, structure and services | Survey, planning check and Building Regulations design |
Comparing Extension Design Fee Structures
Designers use different fee structures and scopes, so like-for-like comparisons require checking the included work and exclusions. Hampshire Build's packages have fixed fees for the stated scope; statutory, third-party and separately agreed additional work are distinct from the package price.
Have a project in mind? Start with a few details about your home.
Check your extension projectCompare Like-for-Like Scope
Ask designers to state whether the fee covers the measured survey, planning drawings and application submission, Building Notice drawings, structural calculations and any tender support. Statutory fees, third-party services and additional work may be separate.
Hampshire Build Fixed-Fee Extension Designer Packages
- Pre-Build Package: £1,950 + VAT for the stated scope
- Premium Package: £2,950 + VAT, including defined contractor tender support
- Premium Plus Package: £3,950 + VAT, including Premium scope, an indicative staged programme and specified pre-construction notices
Real Hampshire Client Savings
Winchester Kitchen Extension:
"Previous designer quoted £4,200 + VAT for drawings. Hampshire Build's Pre-Build Package cost £1,950 + VAT - saved us £2,250 + VAT and included structural calculations the other quote didn't!" - Sarah & James, Winchester
Basingstoke Two-Storey Extension:
"Started with hourly-rate designer, costs spiralling. Switched to Hampshire Build's Pre-Build Package, fixed price gave us budget certainty. Saved at least £2,500 + VAT." - Michael, Basingstoke
Southampton Side Return:
"Got 3 designer quotes: £3,800 + VAT, £4,500 + VAT, £3,200 + VAT. Hampshire Build Pre-Build Package £1,950 + VAT did everything I needed. Saved £1,850 + VAT minimum!" - Claire, Southampton
Why Fixed-Fee Extension Designer Packages Save Money
- Defined fee: The fixed fee applies to the stated package scope; exclusions and additional costs remain separate
- Defined scope: Work outside the fixed-fee package is separate
- 20+ years expertise: We know Hampshire planning inside-out
- Defined package scope: Inclusions and exclusions are set out before instruction
- Clear scope: Each package sets out its design deliverables and defined pre-construction support
What Hampshire Families Get in Our Packages
Pre-Build Package - £1,950 + VAT includes the stated scope:
Ready to apply these ideas to your own home?
Explore your extension options- Measured survey (typically £500-£800 + VAT separately)
- Architectural drawings (typically £1,500-£2,500 + VAT)
- Planning application preparation and submission for the agreed scope
- Building regulation drawings prepared for Building Notice submission (not a Full Plans application)
- Required structural calculations prepared by an independent qualified structural engineer
- Statutory and third-party fees and separately agreed additional work are not included in the package fee
Why Traditional Extension Designers Cost More
- Hourly billing incentivises slower work
- Scope changes charged separately
- Meetings and calls all chargeable
- No economies of scale
- High London-style overheads
Hampshire Build's Extension Design Service Difference
- Local specialists: 150+ Hampshire extensions completed
- Fixed prices: Fixed for the stated package scope, with exclusions shown in the terms
- Clear delivery plan: Drawings follow the agreed package scope; approvals are determined by the relevant authority
- Defined design scope: Planning drawings and building regulation drawings for Building Notice submission
To discuss the project and package scope, book a complimentary consultation or review the package details.
A useful next step for your home
Share a few project details to explore an initial budget and planning view.
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