Set up your roof
You do not need exact measurements to start. A rough length and width of the floor is enough, or just pick the size band that sounds closest. Here is what the builder asks for:
- Shape: lean-to, Edwardian, Victorian, gable end or P-shape. If you are unsure, pick the closest and mention it when you send your details.
- Size: small, medium or large, or your own figures.
- Current roof: 16, 25 or 35 mm polycarbonate, or older or newer glass. This drives the heat figures, not the price.
- Extras: any glazed roof lights, a set of LED spotlights, and whether the gutters and fascia need renewing.
Every range already counts the strip out and recycling of your current roof, panels cut to size in the colour you pick, the fitting itself, the council application and a guarantee that lasts 10 years and is backed by insurance. Nothing is sent to us unless you choose to send it. When the numbers look right, send them through the quote form and a surveyor will book a visit.
Want to check a figure by hand? Everything the builder does is explained in the section underneath it.
The roof builder is at the top of this page.
How the numbers work
No black box. These are the sums behind every result.
The price range
Each roof starts from a fixed sum of £1,700 that every job carries, whatever its size, plus £140 for each square metre of roof. That total is then multiplied by a factor for the shape:
- Lean-to: 1.00
- Edwardian: 1.06
- Victorian: 1.10
- Gable end: 1.12
- P-shape: 1.16
The bottom of your range is that figure less 3%. The top is that figure plus 15%, to allow for pitch, access and trims we cannot see from a form. Both ends are rounded to the nearest £50, and any extras are added at their fixed prices.
Example: a 10 m² lean-to is £1,700 plus £1,400, which is £3,100. Less 3% and plus 15% gives a range of £3,000 to £3,550.
The heat you lose now
Heat escapes through a roof at a rate set by its U-value. The builder uses two sums:
- Watts on a cold evening: U-value x roof area x the temperature difference. The builder takes a 20 degree gap: a comfortable room on a frosty night.
- kWh over a year: multiply U-value, roof area, degree days and 24 hours, then divide by 1,000. For degree days the builder uses 2,150, a typical year for England.
| Roof on the conservatory | U-value used (W/m²K) |
|---|---|
| Polycarbonate, 16 mm | 2.3 |
| Polycarbonate, 25 mm | 1.6 |
| Polycarbonate, 35 mm | 1.4 |
| Glass from before 2002 | 2.8 |
| Low-e glass from 2002 on | 1.2 |
| Larkspur insulated panel | 0.43 |
What that heat costs
Pounds and pence come from the Ofgem price cap that runs from 1 October to 31 December 2026, which sets electricity at 26.32p and gas at 7.97p for each kWh. For gas, the builder assumes a 90% efficient boiler, so each kWh of heat needs a little more than one kWh of gas.
Example: a 10 m² lean-to under 25 mm polycarbonate loses about 826 kWh a year through the roof. With panels it loses about 222 kWh. The difference is about 604 kWh, worth about £159 a year on an electric heater or about £53 on gas central heating.
What the builder cannot see
A form cannot check your frame, measure your overhang or look at the side path. The survey does that, and it is why the guide range becomes one fixed figure afterwards. Our guide to what happens at a survey explains the visit, and the full price breakdown shows what each part of the price pays for.
Questions
How close is the online price to the final quote?
For most roofs the fixed price lands inside the range the builder shows. It can move if the surveyor finds a frame repair, awkward access or a much deeper overhang than a floor size suggests.
Do I have to give my email to see a price?
No. The range appears on screen as soon as you make your choices. You only share details if you decide to send them to us for a survey.
Why does the builder ask what my roof is made of now?
Only for the heat figures. Your current roof does not change the price of the panels, but it changes how much warmth you are losing today.
Are the running cost figures a promise of lower bills?
No. They show heat lost through the roof alone, assuming you keep the room warm through the heating season. Heat it less often and the saving is smaller.
Can I use the builder if my conservatory is an odd shape?
Yes. Choose the nearest shape and size for a starting range, then tell us about the odd bits on the quote form. The surveyor measures every section.
