A warm roof on a conservatory is an insulated solid roof: a structural frame over the existing glazing bars, insulation, a weatherproof covering above and a plastered or panelled ceiling below. It turns a seasonal room into a usable one, and it is the most expensive of the three roof options because it is the only one that is really building work rather than glazing.
What a warm roof installation involves
The old roof comes off. A lightweight structural frame designed for conservatory loadings goes on, usually sitting on the existing ring beam. Insulation goes above the frame with a vapour control layer below it, which is what makes it a warm roof rather than a cold one. Then a covering, commonly a lightweight tile or slate effect panel. Then the internal ceiling, plasterboarded and skimmed or panelled, often with downlights and sometimes with a rooflight to keep some daylight.
The three options priced against each other
A like for like polycarbonate replacement is the cheapest and quickest and leaves the room seasonal. A modern solar control glass unit costs more, keeps the daylight, cuts the summer heat and leaves the frame loading roughly unchanged. A solid warm roof costs the most, changes the room completely, adds significant weight and brings the ceiling, the lighting and often the heating into the job. They are three different products rather than three grades, and the middle one is what most people are actually looking for.
The structure and the regulations
Weight is the first question, because a conservatory frame and base were designed for the roof they came with. A competent installer surveys the existing structure and will reinforce it or decline the work. The second question is the exemption: a conservatory sits outside the Building Regulations partly because its roof is substantially translucent, and a solid roof is exactly what removes that. Settle both before ordering, since a solid roof on an untested frame is the failure that shows up as cracked plaster and doors out of square.
Questions people ask about conservatory roof installation cost
Is a warm roof worth it on a small conservatory?
On a small room the fixed costs of frame, ceiling and making good are a large share of the price, so the cost per square metre is high. Better glazing is often the better value change on anything very small.
Does a solid conservatory roof need building control approval?
Frequently yes, because the change commonly removes the exemption the conservatory relied on. Ask the installer what route they are using and get the certificate at the end.
Will a solid roof make the conservatory dark?
It will unless rooflights are included, which is why most solid roof designs put one or more in. Deciding how many is part of the design rather than an afterthought.