The short answer
A sagging conservatory roof usually comes from one of three causes: glazing bars too weak for the load they carry, a frame that has moved or rotted, or a covering heavier than the structure was built for. The dip is a symptom, so find the cause before anyone covers it up. A roofer can tell which it is by checking the bars, the frame and the fixings.
A dip in the roof line is the frame telling you something. It rarely stays the same size, so it is worth finding out why.
Glazing bars that are flexing
Glazing bars are the aluminium or uPVC sections that run down the roof and hold the sheets or glass units in place. They span from the top of the roof to the eaves beam, and they carry the glazing plus whatever settles on it: rainwater, leaves, moss, snow.
Why do bars bend over time?
A bar that was long for its section, or one fitted with too few supports, can slowly bow under steady load. Heat plays a part too. Plastic and aluminium expand in the sun and contract at night, and every cycle works at the fixings. A bar with a steel core inside is stiffer, which is why a bar without one can show a dip sooner than its neighbour.
You can often spot this from inside. Stand back and sight along one bar against the next. A bar that droops between its ends, or sheets that no longer sit flat against their seals, mark the place. A tight gap closing up or a new gap opening nearby tells you the movement is still going on, and a pencil mark on the bar gives you something to measure against in a month. Take the same photograph from the same spot each time, so the comparison is fair.
Frame movement and rot
On some conservatories the roof itself is sound and the frame beneath it has shifted. Foundations can settle, a window frame can bow, and the eaves beam that takes the roof's load can drop at one end.
Is the dip in the roof or the walls?
Check whether the sag lines up with a crack in the base wall, a window that now sticks, or a gap opening where the conservatory meets the house. Those point to the structure moving, and a roofer cannot cure the roof until someone has looked at why. Timber is a different problem. A softwood eaves beam or wall plate that has been wet for years can rot and lose its grip on the screws, and a screwdriver pressed into it tells you plenty. Soft, crumbling timber that takes the point easily is past saving, while firm wood with a surface stain may be fine once the leak above it is cured.
Where the roof meets the house, water running behind the flashing can soak the timber slowly. Our answer on how a conservatory roof is sealed to the house shows how that junction should be made, and why a rotten plate often traces back to it.
Weight the structure was never built for
Conservatory frames are designed around a particular roof. Put a heavier covering on one without checking the frame, and the load goes up while the support stays the same.
Does a tiled roof overload a conservatory?
It can. Under the Planning Portal's test, Building Regulations approval follows if the new covering is at least 15 per cent heavier than the old, and a check by a structural engineer is the sensible first step. Approved Document A, the structural guidance, treats an increase of more than 15% as a significant change. Where glass or polycarbonate gives way to a solid roof, the frame may need strengthening first.
That is why we survey before we quote. Roofers who price from a doorstep glance are guessing at the one thing that matters most here. We look at the frame, note the existing system and give a plain answer on whether the structure can take the new roof. Our guide to a conservatory frame for a solid roof covers this step in more detail.
What to do about a sag
Do not load the roof or climb up to look. Furniture, planters and heavy blinds hung from the bars all add to the strain, so take them off if the sag looks fresh. Take photos from inside and outside, mark the lowest point on the bar with a pencil, and check again in a few weeks. If the mark has moved, the problem is active.
Can a sagging roof be repaired?
Sometimes. A bar can be reinforced or replaced, loose fixings can be refixed, and a rotted beam can be cut out and repaired. If the whole system is tired, replacing the roof is usually the better buy than patching it, and you should expect a straight answer on which it is.
Water is the urgent part. A dip can hold a pool of rain, which adds weight and wears the seals faster. If you can see pooling, a ceiling stain or sheets pulling away from their seats, tell us. We make the roof safe, then show you pictures of what we found. The written price follows the survey. Our page on conservatory roofs sets out the repair and replacement routes, and the replacement timescale answer shows how long they take.
More on sagging conservatory roofs
Is a sagging conservatory roof dangerous?
It can be. A roof under strain may crack sheets or let glass units slip, and pooled water adds weight. Keep people out from under the lowest point, avoid standing on the roof, and have it looked at soon. A dip that has not changed for months is less urgent than one that is growing.
Do I need Building Regulations approval for a new roof?
Often, yes. A replacement conservatory roof is treated by the Planning Portal as work that has to meet Building Regulations. Ask your building control body before work begins. For Taunton addresses that is Somerset Building Control, on 0300 303 7790, and they can tell you how they want it notified.
The full picture: Conservatory roofs in Taunton ยท More short answers