Why is my gutter sagging?

The brackets are the small clips or arms that hold the gutter to the fascia, the timber strip fixed along the eaves. They carry the gutter and everything in it, so their number and spacing decide how straight the run stays. Brett Martin, a gutter manufacturer, advises supports no more than 900mm apart. A run with fewer brackets than that, or with one missing, bows between the gaps and holds a pool of water that then adds more weight.

The shape of the sag helps with diagnosis. A gentle dip in the middle of a long run points to spacing or a missing support. A drop at one end often means the bracket there has failed, or the board behind it has. A droop at a corner suggests the joint is loaded by two runs. Our page on gutter bracket spacing explains how the layout works, and the figure in the product instructions is the one to follow for your system.

A bracket holds only as well as the board behind it. If the fascia has been wet for years, usually because the gutter above has leaked or overflowed, the timber softens and the screws pull out. You may find the bracket hanging loose on its screw, or the screw head showing a gap behind it. Press a screwdriver gently into the board at the bracket. If it sinks in easily, the sag has a cause that new brackets alone will not cure.

Fixing fresh screws into the same soft wood only delays the failure. The honest repair is to cut out the rotten length and fit a sound board, or to renew the fascia along that stretch, then rehang the gutter. Our pages on rotten fascia boards and replacing soffits and fascias explain the work and how we decide whether to patch or renew. Photographs of the board behind the gutter go with the survey, so you can judge the timber yourself.

A full gutter is heavy. Wet silt, moss and leaves weigh far more than the empty plastic, and a run that holds standing water carries even more. Over a wet winter the load pulls at the brackets and widens the dip. Cold weather can freeze the water in a pool and add to the strain, and it can crack a joint at the same time.

Clearing the run often cures a sag that is only a day or two old, because the gutter springs back once the weight comes off. If it stays down, the brackets have bent or loosened. A sag that appears only after rain and recovers when dry points to weight and fall. Keeping the run clear is the best prevention, because a sag and a spill make each other worse. Never lean on a sagging run from a ladder, since a failing fixing can let go suddenly.

A gutter needs a slight tilt towards the outlet. Brett Martin describes 1mm for every 600mm, and FloPlast gives 1:350 for its MiniFlo system. Those numbers come from makers describing their own systems. A sag that dips below the outlet level makes water run back, and the pool becomes permanent. A run that sags the wrong way is worth correcting even where nothing leaks yet. See gutter fall for more.

Age counts. Plastic goes brittle and loses stiffness, so old gutters flex more under the same load. Checkatrade says no fixed timetable applies to replacing fascias and soffits, because upkeep and material decide how long the boards behind a gutter last. Cast iron holds its shape but rusts at the joints and brackets. On very old systems, replacing the whole run is cheaper than repeated repairs. Our pages on plastic gutter lifespan and replacing 20-year-old gutters help you judge when that point comes.

The repair follows the cause. If the run is sound and the fixings have simply loosened, we re-hang it on new brackets at the right spacing and fall. If the fascia is poor, the board is renewed first. If the gutter is cracked, brittle or split at several joints, a new run is the better value, and tell you that plainly. The aim is a repair no bigger than the fault needs, shown in pictures.

Once surveyed, you get a written quote showing one total. Ask any contractor whether their quote includes VAT and any scaffold, as a low ladder job can become a scaffold job at roof height. Our guttering cost page covers what drives the figure, and the main page for guttering, soffits and fascias lists the work we do. Please do not prop a sagging gutter with timber and leave it, since the load only shifts to another point.