The conservatory is the classic under used room. Built cheaply, roofed in polycarbonate, and unusable for a good part of the year because the roof neither keeps heat in nor keeps it out. Replacing the roof is the single change that most often turns it into a room the household actually uses. It is also a job with real structural and regulatory limits, so it is worth understanding what is possible before someone sells you a solution.
Why the existing roof is the problem
Polycarbonate has almost no thermal mass and modest insulation value, so the room follows the outside temperature closely. It is also acoustically dreadful in rain, which is the complaint people mention first.
Older glass roofs are better but often single glazed or early double glazed units with failed seals, which show as misting between the panes and mean the unit has lost most of its insulating value.
In both cases the walls and floor of the conservatory are usually reasonable. Replacing the roof alone therefore delivers most of the available improvement for a fraction of what rebuilding the whole structure would cost.
Option one: a solid, insulated tiled roof
This converts the conservatory into something that behaves like an extension. A lightweight structural frame is built over or in place of the existing roof, insulated, and finished with lightweight tiles or slates outside and a plastered ceiling inside. Rooflights are usually added to keep daylight in the room.
The result is a room that holds heat in winter, stays reasonable in summer and is quiet in rain. It also usually looks considerably better from the garden than a glazed roof does.
The constraints are weight and regulations. The existing frames and base were designed for a light roof, so a structural assessment is needed, and because the change alters the thermal envelope it normally falls under building control rather than the exemption a conservatory originally relied on.
- Lightweight tile or slate systems designed specifically for this purpose
- Insulation and a plastered internal ceiling
- Rooflights to keep useful daylight
- Structural check on the existing frames, base and any dwarf wall
Option two: upgraded glazing
If you value the light and the glazed character, replacing polycarbonate with modern glass units is a genuine improvement. Current sealed units with solar control and low emissivity coatings behave very differently from what was fitted twenty years ago: less solar gain in summer, less heat loss in winter, self cleaning coatings available, and far quieter in rain.
It keeps the conservatory looking like a conservatory, generally avoids the structural questions a solid roof raises, and is often less disruptive. It will still not perform like an insulated roof, and on a south facing conservatory summer heat will remain a factor even with good glass.
Option three: a hybrid
Part solid, part glazed. A common arrangement puts an insulated solid section over the part of the room nearest the house, where the seating is, and keeps glazing over the outer part or as a run of rooflights.
It is a sensible compromise where the room is used year round but the household does not want to lose the sense of a garden room, and it can reduce the structural load compared with a fully solid roof.
The junction with the house, and other practicalities
Whichever option you choose, the detail that determines whether it leaks is where the conservatory roof meets the house wall. That junction should be properly flashed in lead, chased into the brickwork, not sealed with mastic over the top of the existing.
Two other things are worth planning for. Ventilation, because a warmer, more airtight room with a plastered ceiling can suffer condensation if there is no trickle ventilation or opening rooflight. And drainage, because a solid roof discharges water differently from a glazed one and the existing gutter and downpipe may need upsizing.
Finally, be realistic about the base. If the conservatory base or dwarf wall was built cheaply, no roof will fix that, and it is better to know before you spend the money.
Common questions
Do I need building regulations approval to replace a conservatory roof with a solid one?
Usually yes. Conservatories were often exempt because they were largely glazed and thermally separated from the house. Fitting a solid insulated roof changes that, and the work normally needs building control approval covering structure and thermal performance.
Will my existing frames take a tiled roof?
Sometimes, and this must be checked rather than assumed. Lightweight replacement roof systems exist precisely because standard tiles are too heavy. Anyone quoting for a solid roof should be able to explain how the load has been assessed against your frames and base.
Will a solid roof make the room dark?
Not if rooflights are planned properly. Most solid roof conversions include two or more rooflights, and because the walls remain glazed the room usually still gets plenty of daylight. It will feel different from a glass roof, which some people prefer and some do not.
Is it cheaper than building an extension?
Considerably, because the base, walls and frames already exist. If the existing structure is sound, replacing the roof is the efficient way to make the room usable. If the base or frames are failing, the arithmetic changes and a proper extension may be the better investment.