How Much Does a Sun Room Cost in 2026 UK?
In 2026 UK, a small uPVC sun room costs £8,500–£14,000 fitted; a medium aluminium build (4m x 4m) £15,000–£22,000; a large premium aluminium or glass-roof build (5m x 4m+) £22,000–£32,000. Warm-roof tiled spec adds £2,500–£5,000 over polycarbonate. With Future Homes Standard tightening thermal rules, glazing U-values now drive long-term running costs as much as the headline build price.
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Sun room cost at a glance — 2026 UK
- Small uPVC sun room (3m x 3m): £8,500–£14,000 fitted
- Medium aluminium sun room (4m x 4m): £15,000–£22,000
- Large premium aluminium / glass-roof (5m x 4m+): £22,000–£32,000
- Warm-roof (insulated tiled) upgrade: +£2,500–£5,000
- Bi-fold doors (3-pane aluminium): +£3,200–£5,400
- Solid foundations (concrete raft, dwarf wall): £1,500–£3,500
- Underfloor heating (wet, off main system): +£1,200–£2,200
Build time typically 7–14 working days for a 4m x 4m build; add 1–2 weeks for rendered piers, new openings into the house, or wet underfloor heating commissioning.
Sun room cost by size, 2026 UK
Glazing and roof spec — what changes the price
Polycarbonate roof: cheapest, £0 base — but cold in winter, hot in summer, noisy in rain. Avoid in 2026 unless temporary.
Glass roof (self-cleaning, solar control): +£1,800–£3,500 over polycarbonate. Bright, modern, good thermal performance with low-E coatings (U-value ~1.1 W/m²K).
Warm-roof (insulated tiled): +£2,500–£5,000. Best year-round usability and the only spec that reliably hits Approved Document L when open-plan to the house. Most popular 2026 choice.
Glazed walls — frame choice: uPVC £ (cheapest, 30-yr life), aluminium ££ (slim sightlines, modern, 40-yr life), hardwood £££ (heritage, repaintable, 50-yr+ with care). Aluminium is the fastest-growing 2026 choice for medium-to-large builds.
Planning permission and building regs in 2026
Permitted Development covers most sun rooms on detached/semi/terraced homes if: under 4m deep (detached) or 3m (terraced/semi), under 4m high (3m within 2m of boundary), under 50% of garden land, not forward of the principal elevation. Listed buildings, conservation areas and Article 4 zones need full planning.
Building regs exemption applies only if: under 30m², ground level, separated from the house by an external-grade door, with safety glazing where required (BS 6206). Open-plan layouts and underfloor heating off the main system both trigger full Part L thermal compliance — usually meaning warm-roof and triple-glazing.
Future Homes Standard 2026: the U-value targets for new extensions tightened in 2025/26 (1.0 W/m²K on glazed elements). Get your installer to specify the actual U-value, not just "A-rated" — it matters for re-sale EPCs.
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Frequently asked questions
Small uPVC (3m x 3m) £8,500–£14,000. Medium aluminium (4m x 4m) £15,000–£22,000. Large premium / glass-roof (5m x 4m+) £22,000–£32,000.
Most fall under Permitted Development if under 4m deep (detached) or 3m (terraced/semi), under 4m high (3m within 2m of boundary). Conservation areas, listed buildings and Article 4 zones need full planning.
Exempt only if under 30m², ground level, separated by an external-grade door, with safety glazing. Open-plan or shared heating triggers full Part L compliance.
Sun rooms have a solid (warm-roof) insulated roof for year-round use; conservatories are mostly glass; orangeries have brick or rendered piers with a flat-roof lantern.
7–14 working days for a standard 4m x 4m build. Add 1–2 weeks for rendered piers, new openings into the house, or commissioned wet underfloor heating.
Yes — warm-roof sun rooms typically return 70–100% of cost in added property value (Nationwide/RICS 2025). Polycarbonate-roof builds can devalue the home; warm-roof tiled adds the most.
Sources used in our 2026 figures
- gov.uk — Planning Permission
- gov.uk — Approved Document L
- FENSA — Window & Door Installers
- FMB — Federation of Master Builders
Methodology: Cost figures use BestBuilders' 2026 regional cost model (national cost guides × regional labour index).