Shed roof sagging in Gurgaon: why it dips and how it's put right

A sag in a shed roof often shows up first as a puddle: after rain, water sits in a dip between two supports instead of running off. In Gurugram and Noida, where a monsoon storm can drop a lot of water in an hour, that puddle is heavy, and it pulls the dip deeper each season. Left alone, sheets crack, joints leak and in the worst case the frame bends.

The short answer

Look at where the sag is. Between two purlins, the sheet is spanning too far or is too thin. Along the length of a purlin or rafter, the steel member is too light or has bent. At one corner, a column or joint has moved. Each points to a different repair.

Why shed roofs sag

Purlins too far apart

Every roofing sheet has a maximum span it can cover without sagging. Polycarbonate in particular needs closer purlins than metal. When fabricators space purlins widely to save steel, the sheet dips between them.

Purlins or rafters too light

Thin hollow sections over a long span bend under their own weight plus the sheet, and more under rain or a dust layer.

Too flat a slope

A roof needs a clear fall so water runs off. A nearly flat shed lets water pond in any small dip, and the weight makes the dip bigger, a cycle that keeps going.

Corroded joints or a moved column

A rusted base plate or cracked weld at a column lets one corner drop, racking the frame. See welding joint cracked.

Extra loads

Water tanks, solar panels or heavy dust on the roof, or people walking on it for cleaning, all add load the roof may not have been designed for.

Safe checks

• After rain, look from below or from a ladder at the edge for standing water on the roof. Mark where it ponds.
• Sight along each purlin and rafter from the end. A visible curve means the member has bent.
• Check column bases for rust, cracked welds or lifted base plates.
• Measure the roof's fall roughly: water should run off visibly, not sit.

Repair or rebuild?

Adding purlins, strengthening rafters and correcting the slope are common repairs that keep the existing columns. If the frame is rusted through at many joints, or the whole structure is too light, rebuilding is safer. A new car parking shed or polycarbonate terrace shed designed with the right purlin spacing, slope and section sizes avoids repeat problems. Our car parking shed options guide compares frame and roof types, and the terrace shed cost guide explains why stronger frames cost more. On new steelwork, hot-dip galvanising protects joints longest.

How FabWise handles a sagging shed

1. Send photos from below showing the sag, a photo after rain if you have one, and close-ups of the column bases, on WhatsApp.
2. Give us the rough length, width and sheet type.
3. We'll tell you whether it looks like extra purlins, a slope correction or a rebuild.
4. A site visit in our Delhi NCR cities is ₹99, adjusted against the bill; the work is quoted in writing after it.

Prevention

Clear dust and leaves from the roof before the monsoon from a ladder, not by walking on it. Keep gutters running so water can leave the roof. Don't add water tanks, solar panels or hoardings to a shed without checking the frame can take them.

Related: shed gutter overflowing, polycarbonate sheet cracked and terrace shed leaking. See all sheds and pergolas and sheds and pergolas in Noida.