If a gutter sags, water may overflow or the joints may crack and leak. A bucket of water poured in at the highest point of the system reveals any such defects.
The commonest causes of sagging are broken or bent brackets, or loose fixing screws. Most guttering is supported on brackets screwed either to the fascia boards underneath the eaves of the roof or to the ends of the roof rafters.
To rectify a sagging gutter, remove the defective sections and examine the brackets to see if they are firmly fixed. If they are not, use longer screws to secure them. Where brackets are bent or corroded, replace them with matching new ones.
Replacing a rafter bracket normally involves removing the slate or tile directly above it, though this problem can often be overcome by fixing a fascia bracket adjacent to the faulty rafter bracket to give the necessary extra support.
Ogee section guttering differs from other types in that it is screwed directly on to the fascia. Sagging here is usually caused by the fixing screws rusting and then pulling away from the fascia. In this case, plug the screw holes and fasten with new, galvanized screws.
A common fault with guttering occurs where the slope or fall towards the downpipe outlet becomes distorted – because of faulty installation or settlement of the house itself. Too steep a fall causes water to overflow at the downpipe outlet. Too shallow a one results in a build up of water and sediment along the run.
To determine the correct fall for an incorrectly aligned section, tie a length of twine along the top of the gutter – from the high end to the outflow point – and use it as a guide to reposition the intervening brackets. The gutter should fall 25mm for every 3m of its length.