DIY Academy category

Extensions & Conversions DIY guides.

Planning-first guides for extensions, loft conversions, garden offices, steel beams, first fix, second fix, budgets, materials and UK homeowner decisions.

Beginner · 18 min read House extension first steps for UK homeowners

A UK house extension does not start with digging Cost: planning only; allow money for measured survey, drawings and professional advice before construction; pro: early-stage professional fees often start from a few hundred pounds for advice and can run into several thousand pounds for drawings, structural input and applications before any build cost. Timeline: Realistic total timeline: 2-6 months before work starts for brief, measured survey, drawings, planning/permitted-development checks, structural input, Building Control route, quotes and contractor booking. Construction time depends on scope.

Best for: Homeowners planning extensions, conversions or structural changes who need the correct order before speaking to builders. Call a professional if: Use professionals where planning, Building Control, structural design, party wall, drainage, electrics, gas, fire safety or roof work is involved. Read guide Advanced · 28 min read Single-storey extension guide: planning, cost and build stages

A single-storey extension should be built in a controlled sequence: permission or lawful-development check, measured plans, structural design, building control route, groundworks, foundations, damp protection, walls, steel where specified, roof, windows, first fix electrics and plumbing, insulation, plasterboard, plastering, second fix, decoration, snagging and sign-off Cost: planning only; construction is a professional project; pro: typical UK build guidance often sits around £1,800-£3,500 per m² in 2025, with London, poor access, glazing, kitchens, drainage, VAT, fees and finish level pushing costs higher. Timeline: Realistic total timeline: 3-7 months from first idea to completion. Typical preparation: 4-12 weeks for survey, drawings, planning/permitted-development advice, structural design, Building Control and quotes. Typical on-site build: 8-16 weeks for a straightforward single-storey rear extension; longer for drainage changes, steels, kitchens, high-end finishes, poor access or delays.

Best for: Homeowners planning extensions, conversions or structural changes who need the correct order before speaking to builders. Call a professional if: Use professionals where planning, Building Control, structural design, party wall, drainage, electrics, gas, fire safety or roof work is involved. Read guide Professional only · 24 min read Two-storey extension guide for UK homeowners

A two-storey extension is closer to a small new-build attached to an existing house than a simple home improvement Cost: planning only; this is not a DIY build; pro: typical UK guidance for two-storey extensions is often around £1,650-£3,250 per m² before London premiums, professional fees, VAT, kitchens/bathrooms, drainage and high-end finishes. Timeline: Realistic total timeline: 5-10+ months. Preparation and approvals commonly take 8-20 weeks. On-site construction commonly takes 16-32+ weeks depending on structure, foundations, roof integration, weather, access, neighbours, services and finish level.

Best for: Homeowners planning extensions, conversions or structural changes who need the correct order before speaking to builders. Call a professional if: Use professionals where planning, Building Control, structural design, party wall, drainage, electrics, gas, fire safety or roof work is involved. Read guide Professional only · 22 min read Loft and roof conversion guide: planning, structure and costs

A loft conversion starts with head height, roof structure, stair position, fire safety and Building Control Cost: planning and safe observation only; loft conversion construction is professional work; pro: rough UK guidance: rooflight lofts can start around £28,000-£40,000+, dormers often £40,000-£70,000+, hip-to-gable £50,000-£90,000+, mansard commonly £70,000-£90,000+ before high-end finishes and London premiums. Timeline: Realistic total timeline: 3-7 months from first survey to completion. Preparation/design/approvals commonly take 4-12 weeks. On-site loft conversion work commonly takes 6-12+ weeks, longer for mansard, complex steelwork, bathrooms, stairs or roof changes.

Best for: Homeowners planning extensions, conversions or structural changes who need the correct order before speaking to builders. Call a professional if: Use professionals where planning, Building Control, structural design, party wall, drainage, electrics, gas, fire safety or roof work is involved. Read guide Intermediate · 18 min read Garden office planning guide: regulations, costs and materials

A garden office is still a building Cost: planning and simple kit research; avoid DIY electrics and poor bases; pro: basic insulated garden offices often start from several thousand pounds; more realistic all-in projects with base, electrics, heating, internet and finishes can range from £10,000-£35,000+ depending on size and specification. Timeline: Realistic total timeline: 4-14 weeks for many garden offices. Simple kit build with clear access may be 1-3 weeks on site after ordering. Bespoke insulated office with base, electrics, internet, heating and landscaping can take 4-8+ weeks on site plus lead times.

Best for: Homeowners planning extensions, conversions or structural changes who need the correct order before speaking to builders. Call a professional if: Use professionals where planning, Building Control, structural design, party wall, drainage, electrics, gas, fire safety or roof work is involved. Read guide Beginner · 12 min read First fix and second fix explained for renovations

First fix is the hidden stage: structure, pipework, cables, ventilation routes, frames and services before walls are closed Cost: planning, checking and photo records only; pro: included inside renovation pricing; small first/second fix visits may be day-rate or trade-rate, while multi-room projects require a scoped quote. Timeline: Realistic timing inside a renovation: first fix may take days to several weeks depending on rooms and trades; second fix may take days to several weeks after plastering, drying and decoration readiness. The gap between them matters because walls close and finishes begin.

Best for: Homeowners planning extensions, conversions or structural changes who need the correct order before speaking to builders. Call a professional if: Use professionals where planning, Building Control, structural design, party wall, drainage, electrics, gas, fire safety or roof work is involved. Read guide Professional only · 18 min read Steel beams and RSJs explained for extensions

Steel selection is an engineering decision based on load, span, bearings, wall type, roof/floor loads and deflection limits Cost: not a DIY job; homeowner role is planning, documents and checks; pro: small structural openings may run into several thousand pounds once engineer, steel, temporary works, labour, Building Control and making good are included; complex openings or London access can cost much more. Timeline: 1-4+ weeks for engineer survey, calculations, approvals/Building Control coordination, fabrication and delivery. Installation may be 1-3 days for a straightforward opening but can take longer with temporary works, access constraints, multiple beams or complex making-good.