Cost Guide: How Much Does a UK Conservatory or Extension Really Cost?

Thinking about adding a conservatory, garden room or an extra floor? The first question that pops up is always the price tag. In the UK, costs can swing wildly depending on size, materials, location and the level of finish you want. Below we break down the biggest cost drivers and give you practical ways to keep the budget in check.

Understanding the Main Cost Drivers

First off, size matters. A 10‑square‑metre lean‑to will cost far less than a full‑height, 30‑square‑metre glass structure. As a rule of thumb, each extra square metre adds around £1,200‑£1,800 depending on the glazing type.

Materials are the next big factor. uPVC frames are the cheapest, but aluminium or timber‑frame units with high‑performance glazing can push the price up by 20‑30 per cent. Don’t forget the roof – a simple pitched roof is cheaper than a flat roof with a sophisticated drainage system.

Labour rates vary by region. Builders in the South East often charge 10‑15 per cent more than those up north. If you hire a specialist conservatory company, their overheads may be baked into the quote, but you get a design package and warranty in return.

Planning permission is another hidden cost. Most small extensions fall under permitted development rights, but if you need a full planning application, expect fees of £200‑£500 plus possible architect costs.

Tips to Keep Your Project on Budget

Start with a clear brief. Sketch out the dimensions, decide on a glazing type and pick a finish early. The more detail you give your builder, the fewer change orders later, and change orders are where budgets explode.

Get at least three quotes. Make sure each quote breaks down material, labour, and contingency. Comparing line‑items helps you spot where one supplier is overcharging or cutting corners.

Consider a phased build. You might put up the basic shell now and add internal finishes later when you have extra cash. This spreads the cost and lets you live in the space while it’s being completed.

Factor in a 10‑15 per cent contingency. Unexpected ground conditions, delivery delays or small design tweaks happen all the time. Having a cushion avoids nasty surprises.

Finally, think about long‑term savings. High‑efficiency double or triple glazing reduces heating bills, and a well‑insulated roof can save you £100‑£200 per year. The upfront extra cost often pays for itself within a few years.Bottom line: a basic 12‑square‑metre conservatory can start around £12,000, while a premium, fully‑finished extension can climb above £45,000. By understanding the key cost drivers and planning ahead, you can steer your project toward the price range you’re comfortable with.