The Cost of Change & Remodelling
What it really costs to change the use of a building or remodel a property in the UK — from planning fees to construction, with realistic budgets and value-uplift guidance.
£150-250
Per Sqft Build Cost
10-15%
Typical Contingency
20-30%
Value Uplift Potential
98%
Our Approval Rate
Whether you're converting a commercial building to residential, splitting a house into flats, or remodelling your home to add space and value, understanding the true cost is the foundation of a successful project. Underestimating costs is the single biggest reason property projects run into trouble.
This guide breaks down the real costs of change of use and remodelling projects in the UK — professional fees, application costs, construction rates, and the hidden costs that catch people out. We also cover how to assess whether the numbers stack up before you commit significant capital.
Costs vary significantly by location, building condition, and specification. London and the South East command premium rates; the North and Wales are more affordable. Always get project-specific quotes — but these ranges give you a realistic starting point.
The Four Biggest Cost Drivers
Before looking at specific numbers, understand what makes two similar-looking projects cost very different amounts.
Size & Scale
Larger projects cost more in absolute terms but less per square foot. Economies of scale kick in above ~1,500 sqft.
Structural Works
Removing load-bearing walls, adding extensions, or underpinning significantly increases costs. Layout changes that keep structure intact are far cheaper.
Building Regs Compliance
Fire safety, insulation, ventilation, and accessibility upgrades are mandatory and can add £15-40/sqft to conversion projects.
Specification Level
Basic fit-out vs premium finishes can swing costs by 40%+. Kitchens and bathrooms are the biggest variable per unit.
Change of Use Cost Breakdown
The planning and design stage of a change of use project. These are the costs to get you to an approved planning application — construction costs come separately.
| Cost Item | Typical Range | Notes |
|---|---|---|
| Feasibility & Planning Assessment | £1,500-£4,000 | Site visit, planning research, route advice |
| Planning Drawings | £3,000-£10,000 | Depends on complexity and council requirements |
| Prior Approval Application | £125 per dwelling | Government fee for PD routes |
| Full Planning Application | £578 per dwelling | Where Article 4 or full planning required |
| Building Regulations Drawings | £3,000-£8,000 | Technical construction details |
| Structural Engineer | £2,000-£6,000 | Calculations and specifications |
| Other Consultants (if needed) | £1,500-£5,000 | Ecology, acoustics, heritage, drainage |
Total change of use professional costs: Typically £10,000-£30,000 for a standard project. Complex cases (listed buildings, multiple units, contentious sites) can reach £40,000+. Construction is additional — see remodelling costs below.
Remodelling & Construction Costs
The physical building work. Rates vary by region — these are UK-wide averages. London and South East are 20-40% higher; North and Wales 10-20% lower.
| Project Type | Typical Cost | Notes |
|---|---|---|
| Single-Storey Extension | £1,500-£2,500/sqm | Rear or side extension |
| Double-Storey Extension | £1,800-£2,800/sqm | Per square metre of new floor area |
| Loft Conversion | £35,000-£65,000 | Dormer, hip-to-gable, or mansard |
| Full Refurbishment | £100-£200/sqft | Strip out and refit to modern standard |
| Internal Reconfiguration | £80-£150/sqft | Knock-through, new layouts, plumbing |
| Kitchen Installation | £8,000-£30,000 | Units, worktops, appliances, fitting |
| Bathroom Installation | £4,000-£12,000 | Per bathroom, full fit-out |
Example: Office to 4 Flats Conversion
A realistic budget for converting a 2,500 sqft commercial unit into 4 self-contained flats, including change of use planning and full remodelling.
Project Budget
The Numbers
- £198,000 gross profit on a £482,000 investment — a 41% return on cost.
- 4 rental units generating £4,000-£5,000/month in rental income.
- Project timeline: 9-12 months from planning to completion.
- Actual figures depend on location, specification, and market conditions — get a project-specific assessment.
Hidden Costs to Budget For
These are the costs that catch people out. They're not always quoted upfront but are common across conversion and remodelling projects:
Where Change & Remodelling Adds Value
The cost is only half the equation. Understanding the value uplift helps you decide whether a project is worth pursuing.
Additional Units
Splitting a single dwelling into flats can increase total value by 30-50% in high-demand areas.
Change of Use
Converting commercial to residential often unlocks 2-3x value uplift, especially in London and the South East.
Extension & Loft
Adding a rear extension and loft conversion can add 15-25% to a property's value for a fraction of that cost.
Energy Performance
Improving EPC rating from D to B can add 5-10% to value and reduce running costs significantly.
Want Real Numbers for Your Project?
Every project is different. Generic guides give you a starting point, but a project-specific feasibility assessment gives you real numbers to make decisions with.
We assess your building, planning context, and objectives — then provide a realistic cost estimate and value assessment so you can invest with confidence.
Frequently Asked Questions
Professional fees for a change of use project typically range from £4,000-£15,000 depending on complexity. This includes feasibility assessment, planning drawings, and application submission. Government application fees are separate: £125 per dwelling for prior approval or £578 per dwelling for full planning. Building Regulations drawings add a further £3,000-£8,000 if you proceed to construction.
Change of use focuses on the planning and legal conversion of a property's use class — costs are mostly professional fees and application fees, with construction coming later. Remodelling is the physical building work: extensions, internal reconfiguration, refurbishment. A full project often combines both: change of use to secure the new use, then remodelling to deliver it. Budget for both stages separately.
We recommend 10-15% contingency on construction costs for conversions and remodelling. For older buildings or those with unknown structural conditions, increase to 15-20%. Contingency covers unforeseen issues like asbestos, structural defects, damp, or planning conditions that require additional work. It's better to budget for it and not need it than to run out of money mid-project.
It depends on the property and location, but well-executed change of use and remodelling projects typically deliver 20-30% value uplift. Commercial-to-residential conversions in high-demand areas can deliver even more. The key is understanding the end value before committing — we help clients assess development potential and likely returns as part of our feasibility work, so you can make an informed decision before spending significant capital.