A conservatory is treated like an extension for planning purposes, but for investors and serious homeowners, a well‑designed brick extension usually delivers stronger energy performance, better year‑round usability, and superior long‑term value uplift than a typical glazed conservatory. In short, prioritise a brick single‑storey rear extension where feasible, and use a conservatory only when the brief is strictly about light and seasonal use rather than ROI, EPC enhancement, or rental appeal.

Why this matters

• Investor goals: increase net usable area, protect or lift EPC, and protect Gross Development Value (GDV)—areas where brick extensions outperform most conservatories due to fabric and thermal continuity with the main heated envelope.
• Market evidence: Nationwide’s analysis shows floor‑area‑adding projects like extensions/loft conversions can add up to around 25% to value, more impactful than typical 5–7% conservatory claims cited in consumer media; value still depends on design quality and integration.
• Operational reality: highly glazed rooms suffer bigger heat loss and summer overheating without advanced glazing/fabric, undermining year‑round use and tenant comfort compared with well‑insulated masonry extensions.

Is a conservatory an extension?

• Planning treatment: for planning, conservatories fall under the same householder rules as single‑storey extensions, so the same Class A permitted development limits, positions, and height rules apply to most homes.
• Larger rear option: in England, the neighbour consultation prior‑approval route allows deeper single‑storey rears up to 6m (terraced/semi) or 8m (detached), subject to amenity checks and council confirmation before work proceeds. Link to Larger Home Prior Approval Extension

Value and ROI: conservatory vs extension

Energy and EPC impacts

• Heat loss and glazing: more glass equals higher transmission losses; Energy Saving Trust highlights the role of windows/doors and roofs in overall heat loss, underscoring why conservatories need premium glazing and roof systems to approach extension‑like performance.
• Building regs signal: the common “exempt conservatory” scenario requires thermal separation (external‑quality doors) and independent heating—practically acknowledging it should sit outside the primary heated envelope unless upgraded, which limits day‑to‑day integration and energy efficiency.
• Property Developers View: where EPC defensibility and operating costs matter for lettings or resale, a brick extension designed to Part L standards usually beats retrofitting a highly glazed room to comparable performance levels.

Planning routes and compliance

• Permitted development: standard single‑storey rear limits apply to conservatories as to extensions, typically depth limits from the “original house,” height caps, 50% curtilage coverage, and no building forward of the principal elevation.
• Larger 6m/8m prior approval (England): submit the neighbour consultation application and wait for written confirmation before works start; councils consider amenity impacts, with 21‑day consultation and a defined determination window.
• Building regulations: Conservatories can be exempt only if strict criteria are met (ground‑level, under 30 m², thermally separated, it has its own independent heating, compliant glazing/electrics).Solid or tiled “warm roofs” and any structural opening to the house mean you need building control.

Practical decision checklist

• If ROI/EPC is the priority, contact an architecture firm for a brick extension feasibility first; Choose a conservatory only if you mainly want a bright space for occasional use, or if you’re working with a tight budget and plan to improve it over time.
• If pursuing a conservatory, specify high‑performance glazing, insulated warm roof systems, shading, and airtightness details, or consider an orangery/hybrid that behaves more like an extension.
• Validate PD or prior‑approval eligibility early, then align design and build route with building regulations to avoid rework and delays.

FAQs

• Is a conservatory classed as an extension for planning?Yes—planning rules typically treat conservatories like single‑storey extensions under householder permitted development, subject to limits and conditions.
• Which adds more value: a conservatory or a brick extension?Nationwide data supports larger uplifts where floor area is added via extensions/lofts (up to c.25%), whereas conservatory figures cited in consumer media are often around 5–7% and highly quality‑dependent.
• Are conservatories energy efficient?Not usually without upgrades; their large glazed areas increase heat loss and summer gains, and many are thermally separated under the exemption, signalling lower integration with the main heated envelope.
• Can a solid tiled conservatory roof fix energy issues?It helps, but typically removes the exemption and brings full building regs into play; fabric‑first brick extensions still offer the most robust whole‑home integration.
• Do the 6m/8m “larger extension” rules apply?Yes in England via prior approval/neighbour consultation, with defined neighbour notification and council decision periods before starting work.

Investor’s next steps

• Book a feasibility review to compare a brick rear extension vs a conservatory/orangery on ROI, EPC trajectory, build cost, and programme, including PD vs prior approval appraisal.
• See the Permitted Development Guide and prior approval checklist to scope depth, height, and boundary constraints before concept design.
• Review investor case studies showing floor‑area gains and EPC improvements from fabric‑first extensions to calibrate likely GDV/uplift