Most conservatories built in the 1990s and 2000s are cold in winter, sweltering in summer, and poorly integrated with the rest of the house. A full refurbishment, new roof, proper insulation, and appropriate heating, can transform the space into a room usable year-round. In 2026, a comprehensive modernisation (solid roof, insulation and heating) typically costs £12,000–£30,000, while a focused roof replacement alone runs from about £1,500 for like-for-like polycarbonate to £4,000–£8,000 for a glass roof.

The scope of work you can carry out depends partly on the size and position of the conservatory, which determine whether Permitted Development rights apply, and whether Building Regulations approval is required.1 Getting these distinctions right before you start avoids costly retrospective applications.

What Modernising a Conservatory Typically Involves

A refurbishment project might include any combination of the following:

  • Roof replacement, the single most impactful upgrade, replacing inadequate polycarbonate with a solid tiled, solid insulated, or glazed roof system
  • Wall and floor insulation, cavity wall insulation in the dwarf walls, underfloor insulation beneath the slab
  • Replacement glazing, upgrading single-glazed or early double-glazed panels to modern units with low-emissivity coatings
  • Heating, adding radiators to the house system, underfloor heating, or a standalone electric or infrared solution. Extending the house system into the conservatory ends its Building Regulations energy exemption, so it is then treated as an extension2
  • Internal finishing, plastering solid roof sections, new floor covering, redecoration
  • Structural repair, addressing any subsidence, failed guttering, or corroded aluminium framework

Planning Permission and Permitted Development

For most homeowners, conservatory work does not require planning permission provided the project stays within Permitted Development (PD) limits. The relevant rules under Class A (extensions) of the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended) require that:

  • The conservatory does not extend beyond the rear wall of the original house by more than 4 m (detached house) or 3 m (semi-detached or terraced), unless it is in the expanded 6 m/8 m category, which exists in England only under the prior approval procedure.3
  • A single-storey conservatory is no more than 4 m high, its eaves are no higher than the eaves of the house, and no part of it is higher than the highest part of the house roof.3 Within 2 m of a boundary, its eaves must not exceed 3 m.
  • The ground covered by all buildings other than the original house (extensions, the conservatory and outbuildings together) does not exceed 50% of the curtilage, not counting the ground the original house stands on.3
  • The conservatory is not forward of the principal elevation or a side elevation fronting a highway.3
  • On designated land (a Conservation Area, National Landscape, National Park, the Broads or a World Heritage Site) stricter limits apply: side extensions, rear extensions of more than one storey and the larger 6 m/8 m extensions are not permitted development there.3

Refurbishing an existing conservatory that stays within its current footprint generally raises no planning issues. Changing the roof form (e.g., raising the ridge height, extending the roof area) may take the work outside PD. If in doubt, apply for a Lawful Development Certificate (LDC) from your local planning authority, fee currently £274 in England (half the £548 householder application fee), before starting work.4

Building Regulations

Whether you need Building Regulations approval depends on whether the conservatory meets the statutory exemption criteria. A conservatory is exempt from Building Regulations if:

  • It is at ground level and has a floor area of no more than 30 m²5
  • It is separated from the house by external-quality walls, doors, or windows2
  • The house’s heating system is not extended into it; a separate heater of its own is fine2
  • The glazing conforms to the safety requirements of Approved Document K6

Converting or replacing the roof to a solid construction usually ends the exemption: government guidance is that significantly reducing the glazing in the walls or roof can mean the structure is no longer an exempt conservatory, and the building control body decides case by case.7 You are also changing the thermal envelope and the structural loading on the existing walls and foundations. You will need approval for:

  • Structural (Approved Document A): the existing dwarf walls and foundations must be capable of supporting the additional weight of a solid roof8
  • Thermal (Approved Document L): the new roof must achieve minimum U-values (currently 0.15 W/m²K for a new roof element in an extension)9
  • Ventilation (Approved Document F): adequate ventilation must be maintained10

Your conservatory installer or a structural engineer should confirm whether existing foundations are adequate; many older conservatories were built on shallow concrete strip footings that may need reinforcement before a heavy solid roof can be added.

Roof Replacement Options and Costs

The choice of replacement roof system is the biggest decision in a conservatory refurbishment.

Roof TypeDescriptionTypical Cost (5m x 3m conservatory, 2026)
Polycarbonate (like-for-like)Cheapest option; doesn’t resolve heat/cold issues£1,500–£3,000
Self-cleaning double-glazed glass roofBetter appearance and thermal performance than poly£4,000–£8,000
Solid insulated tiled roof (system roof)Tiled or slated finish; excellent thermal performance£8,000–£16,000
Solid roof with lantern or glazed ridgeCombines light with insulation£10,000–£20,000
Flat solid roof (warm roof construction)For lean-to conservatories; can be finished in GRP or mineral felt£5,000–£10,000

Prices include supply and installation, VAT at 20%, and basic plastering of the internal ceiling. Decorating, flooring, and heating are additional.

Polycarbonate replacement is the cheapest route but does not address the fundamental problem. Even a good multiwall sheet insulates far less well than a solid insulated roof: Brett Martin quotes 1.2 W/m²K for its 32 mm 9-wall sheet, against 0.15 W/m²K for a new solid roof, and polycarbonate is noisy in rain.11 Most homeowners who replace poly with poly are disappointed.

Glass roofs look better and perform significantly better thermally (a double-glazed unit with low-e coating achieves circa 1.0–1.1 W/m²K), but in full summer sun, solar gain is still an issue unless solar control glass is specified. Add a solar control coating (g-value below 0.35), this costs more but dramatically reduces overheating.

Solid tiled roofs offer the best thermal performance and make the space feel like a proper room. The roof is usually insulated between and below the rafters, and reaching the 0.15 W/m²K that Approved Document L sets for a new roof in an existing home typically takes the equivalent of 150 mm or more of PIR, so ask the supplier for a U-value calculation for the exact build-up.2 The trade-off is loss of light from above.

Combination roofs, a solid perimeter with a central lantern or glazed ridge, attempt to resolve the light vs. insulation trade-off. They tend to be the most expensive option but can be the most satisfying in use.

Insulation

Even with a new roof, a conservatory refurbishment should address:

Dwarf walls. Brick cavity dwarf walls can be cavity-filled (circa £300–£600 for a typical conservatory) or internally dry-lined with insulated plasterboard (circa £800–£1,500). Solid brick walls benefit from internal insulated lining.

Floor. An original concrete slab can be overlaid with 50 mm insulated floor board plus a screed or floating floor. This raises the floor level by around 70 mm, check clearance at door thresholds. A full insulated floor upgrade typically costs £1,500–£3,500.

Glazed panels. If the conservatory has uPVC-framed double-glazing installed after 2002, the panels themselves are probably adequate. Pre-2000 single glazing or thin twin-wall polycarbonate side panels should be replaced, factor in £100–£250 per panel.

Heating Options

A conservatory that is properly insulated can be heated effectively. The options are:

Extension of the central heating system. The most cost-effective long-term solution where the conservatory is adjacent to an existing radiator circuit, though it ends the Building Regulations exemption, as noted above. A plumber will charge £400–£800 to run pipework and add one or two radiators. Underfloor heating (wet) can be incorporated into a new floor screed at around £50–£80/m².

Electric underfloor heating. Simpler to install than wet UFH, a mat or cable system beneath a tile or LVT floor. Costs £30–£60/m² for materials; electrician installation circa £200–£400. A new circuit is notifiable electrical work under Part P, so use a registered electrician or notify building control.12 Running costs are higher than gas-fed wet UFH.

Infrared electric panels. Wall or ceiling-mounted panels heat objects and people directly rather than warming the air. They are popular in conservatories because they respond quickly and can be zoned by panel. Expect to pay £200–£600 per panel installed. Inefficient if left on continuously.

Air source heat pump split unit. A wall-mounted indoor unit and outdoor compressor provides both heating and cooling. Well suited to conservatory use where summer overheating is also a concern. Budget £2,000–£4,500 installed for a single-room unit.

Choosing a Contractor

Conservatory refurbishment sits across several trades, the roof installer needs to coordinate with a plasterer, possibly an electrician or plumber, and a decorator. Options:

  • Specialist conservatory company: handles the full project under one contract; more convenient but more expensive and quality varies widely
  • Main contractor/builder: useful where structural work is also needed; can manage subcontractors
  • Trade-by-trade: cheapest if you are confident project managing; allows you to choose each specialist independently

Check whether whoever installs the roof is registered with a relevant scheme. FENSA and similar competent person schemes let installers self-certify replacement windows, doors, roof windows and rooflights in an existing home.13 A replacement solid roof is not on that list, so it normally needs its own Building Regulations application: confirm with the installer who will make it.

Get at least three written quotes specifying the same scope, and ask each contractor to confirm in writing whether Building Regulations approval is included and who is responsible for obtaining it.

Realistic Budget Summary

ScopeApproximate Cost (2026)
Polycarbonate roof replacement only£1,500–£3,000
Glass roof replacement + basic redecoration£5,000–£10,000
Solid tiled roof + insulation + heating£12,000–£20,000
Full refurbishment (roof, glazing, insulation, heating, floor, refit)£18,000–£30,000

These are indicative figures for a conservatory of 12–20 m² in 2026, including VAT. Costs vary by region, access, the condition of the existing structure, and specification.

References (13)

Figures in this note were checked against the sources below on 30 September 2026. Superscript numbers in the text point to them. Every source the site cites, by topic.

  1. 1technicalvery strongThe National Archives, legislation.RN-OWGIY3Schedule 2 Part 1 of the GPDO 2015, development within the curtilage of a dwellinghouse. This is permitted development itself: Class A enlargement and alteration, with the limits and conditions, through the classes covering roof alterations, porches, outbuildings and hard surfaces. Every statement about what can be built without planning permission traces to this Part, and the exclusions at the start of each class are where most projects actually fall out.
  2. 2technicalvery strongMinistry of Housing, Communities and Local Government.RN-L0FCJXThe in-force U-value tables a DIY insulation or door note must quote, with the exact numbers. Table 4.2, limiting U-values for new fabric elements in existing dwellings, sets roof 0.15, wall 0.18, floor 0.18, swimming pool basin 0.25, window 1.4 or Window Energy Rating Band B minimum, rooflight 2.2, doors with more than 60 per cent of the internal face glazed 1.4 or Doorset Energy Rating Band C minimum, and other doors 1.4 or Doorset Energy Rating Band B minimum. Table 4.3, for existing elements, gives a roof threshold of 0.35 and an improved value of 0.16, which is the figure a loft insulation note needs: paragraph 4.12 says a retained element whose U-value is higher than the column (a) threshold, for example through a loft or garage conversion, should be upgraded to the column (b) value. Paragraph 4.13 allows a lesser upgrade only where the improved value is not technically or functionally feasible or would not achieve a simple payback of 15 years or less. Paragraph 4.8 requires a replacement element to be no worse than the one it replaces as well as meeting Table 4.2. Paragraph 4.10 gives the heritage exception: where character must be maintained, a centre pane U-value of no more than 1.2 or low-emissivity secondary glazing. Note 9 records that the timber window concession of 1.6 or Band C ended on 14 June 2023. The 2021 edition came into force on 15 June 2022; a 2026 edition exists at https://assets.publishing.service.gov.uk/media/69c122a6cfa346b9d4704a55/ADL1_2026.pdf.
  3. 3technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-Z0XQ8VParagraph A.1 sets the householder extension limits: buildings may not cover more than 50 per cent of the curtilage (A.1(b)); a single-storey rear extension may not extend more than 4 metres beyond the rear wall of a detached house or 3 metres for any other house, nor exceed 4 metres in height (A.1(f)), rising to 8 metres and 6 metres under the larger home extension route (A.1(g)); an extension of more than one storey may not extend more than 3 metres beyond the rear wall or be within 7 metres of the rear boundary (A.1(h)); eaves within 2 metres of a boundary may not exceed 3 metres (A.1(i)); a side extension may not exceed 4 metres in height, have more than one storey or be wider than half the width of the original house (A.1(j)). Paragraph A.2 removes cladding and side or multi-storey rear extensions on article 2(3) land such as conservation areas. A.3 requires materials of similar appearance and obscure-glazed, non-opening upper-floor side windows unless the opening part is more than 1.7 metres above the floor, and A.4 sets the neighbour consultation (prior approval) procedure with its 42-day determination period.
  4. 4technicalvery strongPlanning Portal, guidance.RN-M2KUCTThe Planning Portal's consolidated guide to planning application fees in England from 1 April 2026, built from the 2012 fees regulations as amended and MHCLG's annual indexation. More usable than the regulations themselves because it puts each application type next to its current fee and its definition. The statutory amounts are in the regulations; this is the readable index to them.
  5. 5technicalvery strongThe National Archives (legislation.gov.uk), legislation.RN-Y7MVZKClass 7 is the conservatory and porch exemption every extension note leans on: the erection at ground level of an extension consisting of a conservatory, porch, covered yard or covered way, or a carport open on at least two sides, is exempt from the building regulations where the floor area does not exceed 30 square metres. Where a conservatory or porch is wholly or partly glazed, the glazing must still satisfy Part K4 and K5.1 to K5.4 and Part N of Schedule 1. Class 6 exempts small detached buildings up to 30 square metres single storey and up to 15 square metres otherwise, which is the garden room threshold.
  6. 6technicalvery strongMinistry of Housing, Communities and Local Government.RN-XH6E39The standard that decides whether a loft ladder is legal and when a raised deck needs a balustrade. Published 3 January 2013, it covers protection from falling, collision and impact including stairs, ladders, ramps, guarding and vehicle barriers. Paragraph 1.31 states that retractable ladders must not be used as a means of escape. Paragraph 1.32 permits a fixed ladder, with fixed handrails on both sides, only for access in a loft conversion containing one habitable room, and only where there is not enough space without altering the existing space for a compliant stair, which is the rule that catches most loft ladder installations. Paragraph 1.29 restricts alternating tread stairs to loft conversions. For a private stair the maximum pitch is 42 degrees (Table 1.1 note 1), the normal relationship between rise and going is twice the rise plus the going between 550mm and 700mm, and for dwellings external tapered steps forming part of the building need a going of at least 280mm. Paragraph 3.1 requires guarding wherever it is reasonably necessary for safety at the edge of a floor, gallery, balcony, roof, light well, basement or similar sunken area. Paragraph 3.2 requires guarding to be at least the height in Diagram 3.1, allows any wall, parapet or balustrade to serve as guarding, and requires it to resist the loads in BS EN 1991-1-1 with its UK National Annex and PD 6688-1-1, with BS 6180 for barrier and infill panel design. Handrails should be positioned 900mm to 1000mm from the pitch line or floor.
  7. 7technicalvery strongDepartment for Communities and Local Government, guidance.RN-1T7DXIDCLG circular letter to building control bodies on the conservatory exemption. It says significantly reducing the glazing may remove the exemption, decided case by case by building control.
  8. 8technicalvery strongMinistry of Housing, Communities and Local Government (GOV.UK).RN-Z6AXUWThe full Approved Document A PDF, which carries the deemed-to-satisfy tables a domestic project is checked against. Section 2E covers foundations of plain concrete: paragraph 2E3 gives the recommended minimum widths of strip foundations in Table 10, keyed to ground type and total load of loadbearing walling per linear metre. Table 10 sets, for rock (not inferior to sandstone, limestone or firm chalk, requiring at least a pneumatic or mechanically operated pick to excavate), a width equal to the width of the wall at every load. For medium dense gravel or sand (requires a pick to excavate, a 50mm square wooden peg hard to drive beyond 150mm) and for stiff clay or stiff sandy clay (can be indented slightly by the thumb), the minimum widths are 250mm at 20 kN per linear metre, 300mm at 30, 400mm at 40, 500mm at 50, 600mm at 60 and 650mm at 70. Firm clay and firm sandy clay (thumb makes an impression easily) start at 300mm. The document also covers minimum depth of strip foundations, wall thickness rules for residential buildings up to three storeys (paragraph 2C10 covers internal loadbearing walls in brickwork or blockwork), buttressing, lateral support by floors and at roof level, interruption of lateral support, wall cladding in Section 3, and Section 5 on reducing sensitivity to disproportionate collapse with the building consequence classes.
  9. 9technicalvery strongHM Government (GOV.UK).RN-IHEXOXThe full Approved Document L Volume 1 for dwellings, 2021 edition with the 2023 amendments, for use in England. This is the statutory guidance on conservation of fuel and power: the U-value tables for new and replacement elements, the rules on when an existing element must be upgraded, controls and commissioning for heating systems, and the notification requirements. If a note quotes a target U-value for a wall, roof, floor, window or door, this is where the number comes from.
  10. 10technicalvery strongMinistry of Housing, Communities and Local Government.RN-QD1SFFTable 1.1 sets minimum intermittent extract rates: kitchen with a cooker hood extracting outside 30 l/s, kitchen without one 60 l/s, utility room 30 l/s, bathroom 15 l/s, sanitary accommodation 6 l/s. Extract terminals and fans other than cooker hoods should be as high as practicable and no more than 400mm below the ceiling; a cooker hood should sit between 650mm and 750mm above the hob if the manufacturer gives no figure. Table 1.7 requires background ventilators of at least 8000mm2 equivalent area in habitable rooms and kitchens for a dwelling, 10,000mm2 for a single-storey dwelling. Background ventilators should be at least 1700mm above floor level and at least 500mm from a fan in the same room. On replacement windows, paragraph 3.14 says new windows must carry background ventilators no smaller than the originals, and paragraph 3.15 gives the fallback minimums where the old size is unknown: 8000mm2 habitable rooms, 8000mm2 kitchen, 4000mm2 bathroom. Paragraph 3.32 confirms that replacing an extractor fan or cooker hood on existing cabling is not notifiable.
  11. 11technicalsupplier figureBrett Martin, guidance.RN-I8X9Q6Manufacturer page for multiwall polycarbonate roofing sheet. It gives a U-value of 1.2 W/m²K for 32 mm 9-wall Marlon ST, a product fact for the comparison.
  12. 12technicalvery strongMinistry of Housing, Communities and Local Government.RN-JYJ3I5The document that decides what electrical work a homeowner may legally do themselves, and the exact list of notifiable jobs. Regulation 12(6A), reproduced at paragraph 2.5, makes only three things notifiable: the installation of a new circuit, the replacement of a consumer unit, and any addition or alteration to existing circuits in a special location. Regulation 12(9) defines special location as, in a room containing a bath or shower, the zone extending vertically from finished floor level to 2.25 metres (or the shower head position if higher) and horizontally 600mm from the edge of the bath tub or shower tray. Paragraph 2.7 states that all other electrical installation work is not notifiable, namely additions and alterations to existing installations outside special locations, and replacements, repairs and maintenance anywhere. Paragraph 2.8 gives worked examples: a built-in cooker is not notifiable unless a new cooker circuit is needed, and connecting an electric gate or garage door to an existing isolator is not notifiable but running a new circuit from the consumer unit to that isolator is. Paragraph 2.2 confirms Part P reaches outdoor work including fixed garden lighting, pond pumps and outbuildings such as sheds, detached garages and domestic greenhouses. Notifiable work must be certified by self-certification by a registered competent person, third-party certification, or a building control body (paragraph 3.1), with the compliance certificate issued within 30 days (paragraph 3.4). Note that Approved Document P is a source of guidance rather than a ban: non-notifiable work still has to comply with BS 7671.
  13. 13technicalvery strongThe National Archives (legislation.gov.uk), guidance.RN-BP3IWGSchedule 3 item 12 lets registered installers (APHC, BESCA, Certsure, HETAS, NAPIT) self-certify sanitary installations in a dwelling that involve no shared or underground drainage.

  1. The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, The National Archives, accessed 14 September 2026. legislation.gov.uk

  2. Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments, HM Government, accessed 29 September 2026. assets.publishing.service.gov.uk

  3. The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, Class A, legislation.gov.uk, accessed 30 September 2026. legislation.gov.uk

  4. Planning Portal: Application Fees England, 1 April 2026, Planning Portal, accessed 30 September 2026. ecab.planningportal.co.uk

  5. The Building Regulations 2010, Schedule 2: Exempt buildings and work, legislation.gov.uk, accessed 30 September 2026. legislation.gov.uk

  6. Approved Document K, Protection from falling, collision and impact, 2013 edition, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  7. Circular letter: Conservatories and porches (30 July 2013), Department for Communities and Local Government, accessed 30 September 2026. assets.publishing.service.gov.uk

  8. Approved Document A, Structure, 2004 edition incorporating 2004, 2010 and 2013 amendments, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  9. Approved Document L, Conservation of fuel and power, Volume 1: Dwellings, 2021 edition incorporating 2023 amendments, HM Government (GOV.UK), accessed 7 September 2026. assets.publishing.service.gov.uk

  10. Approved Document F, Ventilation, Volume 1: Dwellings, 2021 edition, Ministry of Housing, Communities and Local Government, accessed 14 September 2026. assets.publishing.service.gov.uk

  11. Marlon ST Solar Control multiwall polycarbonate sheet, Brett Martin, accessed 30 September 2026. brettmartin.com

  12. Approved Document P, Electrical safety: dwellings, 2013 edition, Ministry of Housing, Communities and Local Government, accessed 30 September 2026. assets.publishing.service.gov.uk

  13. The Building Regulations 2010, Schedule 3: Self-certification schemes and exemptions from requirement to give building notice or deposit full plans, legislation.gov.uk, accessed 30 September 2026. legislation.gov.uk