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 typically costs £8,000–£25,000, though a focused roof replacement alone starts at around £5,000.
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. 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
- 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 under the prior approval procedure.
- The maximum height does not exceed 4 m and does not exceed the eaves or ridge height of the main house.
- The total area of all extensions (including the existing conservatory) does not exceed 50% of the curtilage (garden) of the original house.
- The conservatory is not forward of the principal elevation or a side elevation fronting a highway.
- The property is not in a designated area (Conservation Area, AONB, National Park, World Heritage Site), where stricter controls apply — side and some rear extensions in designated areas require planning permission.
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 circa £120–£240 — before starting work.
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 below 30 m²
- It is separated from the house by external-quality walls, doors, or windows
- It has an independent heating system with its own temperature and on/off controls
- The glazing conforms to the safety requirements of Approved Document K
Converting or replacing the roof to a solid construction triggers Building Regulations in most cases, because you are fundamentally changing the thermal envelope and potentially 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 roof
- Thermal (Approved Document L): the new roof must achieve minimum U-values (currently 0.18 W/m²K for a new roof element in an extension)
- Ventilation (Approved Document F): adequate ventilation must be maintained
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 Type | Description | Typical 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 roof | Better 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 ridge | Combines 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 — polycarbonate panels have a very high U-value (around 1.8 W/m²K for 35 mm multiwall) and are poor acoustic insulators. 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 ceiling is typically insulated to 150 mm mineral wool between rafters plus a foil-backed board, achieving U-values well within Building Regulations requirements. 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. 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. 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 that whoever installs the roof is registered with a relevant scheme — FENSA registration covers glazing installations and allows self-certification against Building Regulations for the glazing elements. For the structural and insulation aspects of a solid roof, a separate Building Regulations submission may still be required — confirm with the installer.
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
| Scope | Approximate Cost (2026) |
|---|---|
| Polycarbonate roof replacement only | £1,500–£4,000 |
| 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.
