Summary

The orangery vs conservatory distinction is not just architectural fashion — it has direct Building Regulations consequences that affect cost, design, planning, and what trades are needed. A conservatory is a permitted exempt structure under Schedule 2 of the Building Regulations (Class VII), provided it meets the four criteria. An orangery does not meet those criteria (mainly because of the solid roof perimeter and integration with the house) and is therefore a regular extension subject to Part A (structure), Part L (energy), Part F (ventilation) and so on.

For the customer, the difference is often emotional ("orangery sounds posher than conservatory") but for the builder, it's contractually critical. Pricing an "orangery" as a conservatory under exempt rules means missing Building Regs cost (£500–£1500 inspection fees plus structural calcs and Part L specification). Pricing a conservatory as a full extension means quoting too high and losing the job.

Mid-range to premium installations in the last 5 years have shifted heavily toward orangery/garden-room style — solid roof, lantern centre, masonry walls with large glazing — because Part L 2022 made fully-glazed conservatories thermally awkward and customers wanted year-round usable space.

Key Facts

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Feature Conservatory Orangery
Wall construction Mostly glass Brick/block with large glass panels
Roof construction Glass / polycarbonate Solid (flat or pitched) + central lantern
Building Regs Exempt (if criteria met) Full Building Regs
Part L compliance Not required Required
Heating Independent (not extending house heat) Integrated with house heating
Door between house & extension External quality doors required Often open-plan; doors optional
Foundations Often dwarf walls on shallow base Full strip foundation, 750mm+
Cost per m² (mid-range) £1,500–£2,500/m² £3,500–£5,500/m²
Year-round usability Cold winter / hot summer Comparable to main house
Planning treatment PD usually applies PD usually applies but treated as extension
Glazing safety Safety glass required (critical locations) Same
EPC impact Excluded from main house EPC Included as habitable space
Listed building suitability Difficult — must be reversible Standard extension consent

Detailed Guidance

The four exemption criteria for a conservatory

For a conservatory to be exempt from Building Regs under Class VII of Schedule 2:

Class VII Exemption Checklist
1. Floor area ≤30m² (measured internally)
2. Single storey, at ground level only
3. Glazing complies with safety requirements of Part N (critical locations)
4. Thermal separation from the dwelling:
   - External-quality doors between dwelling and conservatory
   - Separate heating system with own temperature and timing controls
   - At least 50% of side walls and 75% of roof glazed

Fail any one of these, and full Building Regs apply.

What "external-quality doors" means

The doors between the house and conservatory must be the same standard as if the conservatory wasn't there — typically a thermally-broken aluminium or PVCu door with good seals, or a high-spec hardwood door. The purpose is to thermally isolate the house from the conservatory so the conservatory can be left unheated without losing heat from the house.

In practice, this means:

Independent heating

The conservatory must have its own heating with separate controls — typically an electric panel heater or a stand-alone gas heater. Extending the main house heating system into the conservatory (e.g. running a radiator off the main system) fails the exemption.

Common compliant heating:

Part L implications for orangeries

An orangery is treated as a normal extension under Part L. Typical fabric requirements (Part L1B 2022):

The lantern roof glazing in an orangery is a Part L critical detail — large area, double or triple glazed argon-filled, low-E coated, often warm-edge spacer. The frame profile must be thermally broken (aluminium with PA66 break or PVCu).

Foundation and structural treatment

Conservatory:

Orangery:

Roof construction

Conservatory roof:

Orangery roof:

Glazing safety (Part N / Part K)

Both orangeries and conservatories must comply with Part K (Protection from falling, collision and impact) for critical glazing locations:

Critical glazing: toughened glass (BS EN 12150) or laminated glass (BS EN ISO 12543). The "BS EN ISO 12543" or "BS EN 12150" stamp should be visible.

Planning treatment

Both can usually be built under permitted development (Class A of the GPDO), subject to size and height limits:

Some local authorities have Article 4 Directions restricting PD for glazed extensions.

Conversion (conservatory → orangery → habitable extension)

Many homeowners build a conservatory, then later upgrade:

  1. Conservatory → Orangery — add solid roof or insulated wall sections; requires Building Regs application as the structure no longer meets the exemption criteria
  2. Conservatory → Heated room — remove doors between house and conservatory, connect heating; requires Building Regs as the thermal separation no longer exists
  3. Orangery extension — additional volume; full Building Regs

In all cases, the existing structure is reassessed under current Building Regs — older conservatories often need significant upgrade work (additional insulation in walls, roof rebuild, new foundations) to comply.

Common pitfalls

Pitfall Consequence Avoidance
Conservatory >30m² Exemption lost; needs full BR Reduce floor area or accept full BR
Open-plan into kitchen Exemption lost Install external-quality doors
Radiator from house heating Exemption lost Separate heating, separate controls
Solid roof retrofit Exemption lost New Part L application
Cheap polycarbonate roof Leaks within 5–10 years Specify glass roof or solid orangery roof
Lantern not centred on opening Visual mismatch with room below Set out from inside room layout, not external dimensions
Wrong glass thickness in lantern Bowing / cracking under snow Engineer-spec glass for the panel size
No ventilation in glass roof Heat build-up in summer Trickle vents or opening rooflights in lantern

Frequently Asked Questions

Can I have an orangery without Building Regs?

No — orangeries almost always require Building Regs because they don't meet the conservatory exemption criteria (specifically the >75% roof glazing rule and >50% wall glazing rule). The lantern style of orangery roof typically has 30–50% glazing only — outside the exemption.

What size lantern fits a typical orangery?

For a 4 × 4m orangery, a 2.4 × 1.8m or 2.0 × 1.5m lantern is typical — sized to suit the room dimensions and structural opening. Larger lanterns (3.0 × 2.0m+) are available but need engineer-sized roof structure. Lanterns are kerb-mounted on a built-up upstand (typically 200–300mm above the flat roof).

Do I need an architect for an orangery?

For most domestic orangeries, an architectural technician's drawings suffice — full architects are typically used for high-end designs or where the orangery integrates with significant remodelling. Drawings need to be detailed enough for Building Regs (foundations, structure, U-values, glazing schedule, drainage).

What's the lifespan of a conservatory vs orangery?

Conservatory (modern glass roof + PVCu frame): 25–35 years before significant refurbishment. Orangery (masonry + solid roof + lantern): 50+ years comparable to the main house, with lantern glass refresh every 20-25 years.

Will an orangery add more value than a conservatory?

Typically yes. An orangery is treated by surveyors as habitable space and counts toward the property's habitable square footage in valuations. A conservatory is generally excluded or weighted at 25–50% of habitable value. Anecdotal evidence (Rightmove / Zoopla analyses) puts orangery value uplift at 1.5–2× the value uplift of an equivalent-cost conservatory.

Regulations & Standards