Conservatory extension cost, and when a conservatory becomes an extension

How conservatory extension cost works

1. Settle whether it is permitted development. A great many conservatory are permitted development, which means no planning application, but the limits on depth, height, materials and how much of the plot is already built on are specific and a designer should read them against your own house before anybody prices anything.
2. Get drawings and a structural design. Existing and proposed drawings, then a structural engineer's calculations for whatever is being opened up or carried. On a conservatory this is a small share of the total and it is what turns an idea into something three builders can price identically.
3. Serve the party wall notices in time. Work on or near a shared wall, or excavation within three or six metres of a neighbour's foundations, engages the Party Wall etc. Act and the notice periods are set in months rather than weeks. Serving late is the commonest reason a start date slips.
4. Price it against a specification, not a sketch. Ask each builder to price the same written specification, with provisional sums shown as provisional sums. Two quotes that differ by a third almost always differ in what is included: the kitchen, the flooring, the decoration and the drainage diversion are the usual absentees.
5. Agree stages, retention and building control. A staged payment schedule against completed work, a small retention until sign-off, and a clear statement of who is notifying building control. The completion certificate is what a future buyer's solicitor will ask for.

Insurance and paperwork

Common questions

When is a conservatory exempt from building regulations?

Broadly when it is at ground level, under a size limit, mostly glazed in walls and roof, thermally separated from the house by doors, and does not affect existing drainage or means of escape. Losing any of those conditions brings the regulations back.

Why are quotes so different?

Because base and glazing specifications differ enormously. A dwarf wall on proper foundations with a good roof glazing system is a different product from a lightweight base and a polycarbonate roof, and both are sold as conservatories.

Is a solid roof conservatory still a conservatory?

Usually not, in regulatory terms. Replacing a glazed roof with a solid one changes the thermal and structural picture and normally makes it a building regulations matter, which is a common and expensive surprise.

Registered contractors by region

• Registered roofers in the East Midlands postcode area
• Registered roofers in the East of England postcode area
• Registered roofers in the London postcode area
• Registered roofers in the North East postcode area
• Registered roofers in the North West postcode area
• Registered roofers in the Scotland postcode area
• Registered roofers in the South East postcode area
• Registered roofers in the South West postcode area
• Registered roofers in the Wales postcode area
• Registered roofers in the West Midlands postcode area
• Registered roofers in the Yorkshire and The Humber postcode area