Planning a single storey extension in London requires understanding both the design planning process and realistic pricing. Many homeowners underestimate either the planning complexity or the costs involved. Understanding what comprehensive planning includes and what realistic pricing looks like helps you budget appropriately. Single-storey extensions solve genuine space constraints for London families. They’re achievable projects when properly planned. They deliver excellent value when executed well. Getting the planning and pricing right from the start prevents expensive surprises later.
Single Storey Extension Plans: Design Process Explained
Comprehensive single storey extension planning begins with a professional site assessment. Architects visit your property. They understand existing conditions. They identify structural constraints. They assess ground conditions. They recognize opportunities your space offers. They evaluate what’s actually feasible on your specific property. This assessment produces detailed reports showing findings and initial recommendations.
Concept design planning creates multiple design directions rather than presenting single solution. Architects explore different layouts. Different styles. Different approaches to solving your space problem. Different configurations for kitchens, living areas, or bedrooms. You review all options. You choose direction you prefer. This exploration ensures final design reflects your actual vision rather than architect’s assumptions.
Detailed design planning translates approved concepts into construction-ready documents. Architects produce technical drawings showing exactly what will be built. Materials specified. Dimensions detailed. Connections clarified. Structural requirements calculated. Electrical and plumbing routing determined. Every detail is shown clearly. Contractors use these documents to understand precisely what’s required.
Planning permission planning assesses whether Planning Permission is required. Many single storey extensions qualify for Permitted Development without formal Planning Permission. Architects determine whether your extension qualifies by assessing depth limits, garden coverage limits, and height restrictions. If Planning Permission is required, architects prepare strategic applications that address typical Planning Committee concerns in your neighborhood.
Building Regulations planning ensures compliance from the design stage forward. Architects design with Building Regulations integrated from the start. Insulation levels specified. Ventilation systems are designed. Fire safety is considered. Structural soundness calculated. Building Regulations coordination happens throughout the design process.
Contractor coordination planning helps identify reliable builders. Architects prepare clear specifications. They coordinate tender processes. They evaluate bids. They recommend contractors based on experience and working relationships.
Single Storey Extension Pricing in London: Cost Breakdown
London single storey extension pricing varies significantly based on multiple factors. Understanding what drives costs helps you budget realistically.
In central London, construction costs typically range from 2,000 to 2,800 per square meter. For a 25-square-meter extension, construction costs might range from 50,000 to 70,000. Add professional fees typically 10 to 15 percent. Add contingency 10 percent. Total project cost probably runs 65000 to 90000.
In outer London, costs are moderately lower. Typically 1800 to 2400 per square meter. For a 25 square meter extension, total project cost might run 60000 to 80000.
Outside London entirely, costs drop substantially. South East typically 1400 to 2000 per square meter. Midlands typically 1200 to 1800. North typically 1100 to 1600.
These are 2026 prices reflecting current material and labor costs. Prices have increased from 2025. Material costs remain elevated. Labor costs increased. Building Regulations compliance adds cost.
What Affects Single Storey Extension Pricing
Ground conditions matter significantly. Good stable ground costs less. Poor ground requiring deep foundations incurs higher costs. Clay soil or contamination adds cost substantially.
Building condition affects pricing. Properties in good condition cost less. Buildings with complications cost more. Asbestos or hazardous materials add significant cost.
Design complexity affects pricing. Simple rectangular extensions cost less. Complex shapes with multiple angles cost more. Unusual proportions cost more.
Material choices matter. Budget materials cost less. Premium materials cost more. Matching existing London brick costs more than standard brick.
Finish quality affects costs. Budget finishes cost less. Mid-range finishes are typical. Premium finishes add 20-30 percent.
Planning complexity affects costs. Simple Permitted Development approvals cost less. Planning Permission applications cost more. Complex approvals with revisions cost substantially more.
Roof complexity affects costs. Simple pitched roofs cost less. Flat roofs cost differently. Complex roofs cost more.
| Cost Category | Budget Option | Mid-Range | Premium | Impact |
| Location | Outer London | Mid London | Central London | ±20-30% |
| Ground Conditions | Good | Mixed | Poor/complicated | ±15-20% |
| Design | Simple rectangular | Standard | Complex shapes | ±10-15% |
| Materials | Budget grade | Standard quality | Premium/bespoke | ±20-25% |
| Finishes | Basic | Mid-range | Luxury | ±25-30% |
| Kitchen/Bathroom | Budget spec | Mid-range | Premium brands | ±20-35% |
| Planning | Permitted Dev | Some revision | Multiple revisions | ±10-15% |
| Professional Fees | 10% | 12% | 15% | Variable |
| Contingency | 8% | 10% | 12% | Budget safety |
| Total Project | £40-60k | £60-85k | £85-120k+ | All combined |
Planning Timeline and Pricing Relationship
Planning timelines directly affect pricing. Quick projects cost less. Extended projects cost more due to professional time.
Permitted Development extensions complete quickly. Design planning 6-8 weeks. Building Regulations 8-12 weeks. Construction 8-12 weeks. Total 4-6 months. Costs are lower because Planning Permission isn’t required.
Planning Permission extensions take longer. Design planning 6-8 weeks. Planning Permission 8-12 weeks typically, sometimes longer. Building Regulations 8-12 weeks. Construction 8-12 weeks. Total 6-9 months. Costs are higher due to the addition of planning application costs.
Complex planning situations take even longer. Revisions requested. Multiple submissions needed. Timeline extends to 9-12 months or more. Costs increase substantially.
Single Storey Extension Pricing Strategy
Getting realistic pricing requires getting multiple quotes. Different architects price differently. Different contractors price differently. Understanding the range helps you evaluate value.
Don’t just look at lowest cost. Cheap often means shortcuts. Experience matters. Quality matters. Reputation matters.
Don’t just choose highest cost. Expensive doesn’t always mean best. Some architects and contractors charge premium prices without delivering proportional value.
Compare what’s included in each quote. Some include more services. Some include less. Understanding what’s included helps you make accurate comparisons.
Get detailed breakdowns. Understand where costs go. Challenge estimates that seem high. Ask about options that reduce cost if necessary.
Extension Architecture: Transparent Pricing
Extension Architecture provides transparent single storey extension planning and pricing. They break down costs clearly. They explain what drives each component. They provide realistic, property-specific total project costs.
They plan comprehensively. Design planning. Planning strategy. Building Regulations coordination. Contractor selection. Site supervision. Complete project management.
They deliver on budget and timeline. Professional planning prevents expensive surprises. Quality delivery means projects complete successfully.
For your single storey extension in London, Extension Architecture provides transparent planning and realistic pricing. Contact them for consultation and detailed quote for your specific property.
