Double Storey Extension Cost in Frognal
Detailed cost guide for double storey extension cost in Frognal, NW3. Budget, mid-range, and premium estimates with local context.
Two-storey rear or side extension adding significant floor space — almost always requires full planning permission. In Frognal, local planning context and property characteristics shape both design approach and cost.
Typical construction duration is 16-24 weeks, excluding design, approvals, and procurement phases.
Conservation area status in Frognal typically adds 10–20% to costs for this project type.
| Specification | Typical Cost Range |
|---|---|
| Budget | £70,000–£110,000 |
| Mid-Range | £110,000–£170,000 |
| Premium | £170,000–£250,000 |
Costs are per project. Typical duration: 16-24 weeks.
Double Storey Extension Cost in Frognal: Cost Breakdown
Two-storey rear or side extension adding significant floor space — almost always requires full planning permission. In Frognal (NW3), this type of project is common among homeowners looking to add space, improve functionality, or increase property value. Understanding realistic cost ranges before appointing professionals helps you set appropriate budget expectations and make better decisions about specification level.
Based on typical NW London pricing, a double storey extension cost in Frognal ranges from £70,000–£110,000 (budget specification) to £170,000–£250,000 (premium specification) per project. The mid-range estimate of £110,000–£170,000 per project represents good-quality finishes with some premium elements — this is where most homeowners in NW3 tend to land.
In Frognal, conservation area status typically adds 10–20% to double storey extension cost costs due to heritage-sensitive material requirements, specialist design work, and extended planning timescales.
The housing stock in Frognal — primarily georgian houses, victorian houses, edwardian houses — influences how double storey extension cost projects are approached. Structural considerations, existing building condition, and plot characteristics all affect both design options and final costs.
Typical construction duration for a double storey extension cost is 16-24 weeks. This excludes design development, planning applications (where required), and procurement phases, which can add 3–6 months before construction starts. In Frognal, conservation area planning processes may extend timescales further.
Cost factors that most affect double storey extension cost pricing include: specification level (the difference between budget and premium finishes can be 2–3x), structural requirements, access and logistics, party wall obligations, and professional fees. Architect fees for this type of project typically run 8–15% of the construction cost, with structural engineering, party wall surveying, and planning consultancy as additional items.
We recommend comparing at least two professional quotations before committing to a double storey extension cost in Frognal. Our free matching service can connect you with vetted local professionals who have specific experience with this project type in your area. Submit your brief once and we'll introduce suitable architects and contractors — there is no obligation after the initial matching.
Key Cost Factors
- double storey extension cost
- two storey extension cost
- two storey rear extension
Typical Project Timeline
- Initial cost estimation and budget planning.
- Professional appointments — architect, structural engineer, surveys.
- Design development and planning applications (where required).
- Contractor procurement and quotation comparison.
- Construction phase: 16-24 weeks.
Frequently asked questions
A double storey extension cost in Frognal typically costs £70,000–£110,000 (budget), £110,000–£170,000 (mid-range), or £170,000–£250,000 (premium) per project. Final costs depend on specification, site conditions, and design complexity.
Related Project Costs in Frognal
Rear Extension Cost
£35,000–£55,000 to £85,000–£130,000
per project
Loft Conversion Cost
£40,000–£60,000 to £90,000–£140,000
per project
Full House Renovation Cost
£100,000–£200,000 to £400,000–£800,000+
per project
All costs in Frognal: Renovation costs in Frognal
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Hampstead Renovation Costs is an information and matching service operated by Hampstead Renovations Ltd. We are not a building contractor.