Many Cornish homes have a conservatory that seemed like a good idea at the time but is now too hot in summer, too cold in winter and too noisy in the rain. Rather than putting up with it, more homeowners are replacing the conservatory with a proper extension that works all year round. This guide looks at your options, what to check on planning and Building Regulations, and how to think about cost.
Signs your conservatory has reached the end
A conservatory may be worth replacing if:
It's uncomfortable to use for most of the year, and you rarely sit in it.
The glass or polycarbonate roof is cloudy, leaking or noisy in heavy rain.
The frames are tired, with condensation between panes or failing seals.
You'd like the space to be a proper kitchen, dining room, living room or home office.
You want to improve the energy performance of the house and the look of the back or side.
Before deciding, ask whether the base and frame are sound. Many older conservatories sit on shallow foundations that aren't suitable for a heavier, insulated structure.
Three ways to upgrade
1. Replace the roof only. Swapping an old roof for a solid insulated roof, or a high-performance glass roof, is usually the cheapest route. It improves comfort, but the walls, floor and frames stay as they are, and the result is limited by the original structure.
2. Rebuild as a conservatory-style room. A new orangery or glazed extension with a solid roof and lantern can look similar but behaves much better. It generally needs new foundations and insulated walls.
3. Replace it with a full extension. Taking the conservatory down and building a new masonry or timber-frame extension gives you a fully insulated space with proper foundations, wall finishes and heating. It's the most expensive route, but it adds the most usable space. If you're thinking about this, see our guide to kitchen extensions in Cornwall, and our general home extensions page.
Roof options
The roof makes the biggest difference to comfort. Common choices include:
Lightweight insulated tiled roofs, which look like a normal roof from inside and out and give the best temperature control.
Warm roof systems with insulation above the structure, often combined with roof lanterns for daylight.
Glass roofs with solar control coatings, which keep light levels high but may still give less thermal comfort than solid roofs.
Hybrid roofs that combine solid sections with glazing, such as a lantern or rooflights.
Wind and rain are real factors in Cornwall, particularly near the coast, so the roof's weatherproofing and fixings need as much thought as the look of it. Our guide to weatherproofing coastal homes is a useful companion.
Planning permission and permitted development
Conservatories and extensions to houses can often be built under permitted development rights, which means no planning application is needed if you stay within certain limits on size, height, materials and position. These rights are restricted or removed in some situations, including:
Conservation areas and protected landscapes, where limits on materials and positions are tighter.
Listed buildings, which need listed building consent for most changes.
Properties where permitted development rights were removed by an earlier planning condition.
Flats and maisonettes, which don't have the same rights as houses.
There are also rules about height, how far an extension can project from the original house and how close to a boundary it is. Because the details are specific, check with Cornwall Council, or ask about a lawful development certificate, before you start. Our planning permission guide covers the basics.
Building Regulations
Many conservatories are exempt from Building Regulations, but only if they meet certain conditions, such as being at ground level, being under a certain floor area, and being separated from the house by external-quality doors and walls. Replacing a conservatory with a heated, insulated extension, or removing the separation, will generally mean Building Regulations apply. That typically covers:
Foundations and structure.
Insulation and energy efficiency.
Ventilation, drainage and electrical safety.
Fire safety and means of escape, particularly if the extension affects an escape route.
Safety glazing in doors and low-level windows.
Your builder or designer should explain how Building Control will be handled. Our Building Regulations guide covers the process, and our home extension article gives more background on the build itself.
Thinking about cost
Costs vary widely depending on size, design, ground conditions and finish, so treat any figures as general guidance only. As a rough idea:
A replacement solid roof on an existing conservatory is usually a smaller project than a full rebuild.
A new full extension is typically priced per square metre, with a wide range depending on the specification and whether it includes a kitchen, bathroom or structural openings.
Costs are higher where access is difficult, ground conditions are poor or the design includes large glazed doors and structural steel.
The only reliable way to know is to have the project properly specified and priced. Our project management and QS services can help with budgeting.
Conservatory replacement FAQs
Can I just replace my conservatory roof?
Often yes, if the frame and base can support it. A structural check is important, and Building Regulations may apply.
Will a bigger extension need planning permission?
It may. Permitted development has limits on size and height, and some areas have tighter restrictions. Check with Cornwall Council.
How long does a conservatory replacement take?
It depends on the scope. A roof replacement can be quick, while a full extension needs time for groundworks, structure, weatherproofing and finishes.
Will the new extension affect my home insurance?
It's wise to tell your insurer about the work. They may need details about what's being built.
Talk to us about your project
If your conservatory isn't working any more, we can help you work out what to do next. Call Cornish Building Company on 01208 816991 or contact us to talk through your plans.
