Defective rainwater guttering and pipework can be the source of many sorts of damp problems in the structure of a building. The guttering and associated pipework are designed to carry rainwater away from a building, if they are not properly maintained, the water can run down the outside wall, eventually causing damage within the structure, ruining the decoration and/or causing mould growth. It is important to keep the guttering and pipework in good repair.

The best time to carryout work on the gutters is in the late autumn, after all the leaves have fallen - so you can clean them out of the guttering before they cause over winter problems. Often problems are only apparent while it is raining, so keep a lookout whenever it is raining for any rain water leaking from the gutters or running where it should not. If you notice any major leaks at any time of the year, treat the repair as a priority.

Whenever working at heights, use a ladder correctly positioned. Take care when working at the top of a ladder, do not try to overreach yourself, and take care when handling lengths of guttering at heights - especially when you are handling metal or cement guttering which is fairly heavy and can affect your balance. For extensive repairs, you may consider hiring a scaffold tower system - it will make working at heights easier but unless your tower has wheels and can be moved around the building, considerable effort is required to dismantle and reposition the tower. If the guttering is at a height of over 6m (20 ft) or you are worried about working at height, maintaining/repairing guttering is a job you should avoid doing it yourself.

Common problems

Gutter blockages
If water is seen coming over the side of the guttering during heavy rain, it may indicate that there is a build-up of rubbish laying in it. It is surprising how much rubbish can build up, the common sources are leaves from nearby trees, moss and other growths from the roof, rubbish washed off the roof, scraps of food dropped by birds etc. If you start to look up at guttering around buildings, it is surprising how often you see plants growing up there, these plants must have a root system and that indicates a build up of dirt and rubbish.

If there is a hopper in the down pipe run, clean it out before starting at a higher level.
Scoop out the rubbish from the guttering using a trowel or a piece of card bent into a scoop within the profile of the gutter. To prevent the down pipe becoming blocked, do not push the rubbish into the top of the downpipe. When you have removed all of the solid rubbish and most of the soft rubbish, flush the guttering with water (the best method is to use a hosepipe - even if you get funny comments from the neighbours - usually something about a roof garden). Start next to the downpipe and work away from it, and then work back to the downpipe. If the water fills up the downpipe and then starts to fill the guttering, the downpipe is blocked and that the next job. If there is a hopper in the down pipe run, overflowing at the hopper will obviously indicate a blockage below the hopper.

Clearing downpipes
Be careful when trying to unblock a down pipe, if you try to push the blockage downwards, you might just compress the rubbish and make it harder to remove. Place a bowl at the bottom of the pipe at ground level to prevent rubbish entering the drain.
Try and free the blockage by using a length of stiff wire. Try to get a small hole through the blockage and then work the wire back and forth, dislodged debris will be carried away by the water flowing through the small hole. As the water runs away, use a hosepipe above the blockage to keep the water flowing. As the blockage is cleared, try to feed the hosepipe (with the water running) down the pipe.

If the blockage is such that you cannot force the wire through it (and if the down pipe is straight), try using a thin cane to force a hole through the debris.

If all else fails, the down pipe will need to be dismantled and the individual lengths cleared. To prevent further blockages fit a cage into the top of the downpipe, or a length of gutter mesh over the entrance.

Correcting sagging guttering
Guttering is normally fixed to give a slight slope, from 5-25mm in 3m (1/4 in to 1 in in 10ft), down towards the downpipe. If water collects along the run of the guttering, then you may need to reposition it. If the pool of laying water is only about 5mm, you do not need to do anything, but if the water collects to over 25mm, you do. Between 5 and 25 mm means that you may have a problem developing - check the spacing between the support brackets, if they are too far apart (often 1m maximum but it does depend upon the particular design of guttering fitted), fixing additional brackets may avoid future problems.

If you have plastic guttering in good condition, it is probably easiest to remove the affected section.

Then fix a string line along the top of the guttering between the corners of the building - this assumes that the side is all sloped in one direction. This may not be the case. If there is a downpipe along the run, that should be the lowest point so fix one end of the string there. Alternatively, the side may run both ways to separate down pipes, looking at the string line will show where the highest point is.

Measure down from the string at various points along its run, the distance should be fairly constant as the string should reflect the slope of the guttering. Check the distance where the guttering was sagging - and try to identify the source of the problem. Was the guttering originally set too low, have the brackets just worn low ? If the brackets have just become low with age, do you need additional brackets ? If you decide to add additional brackets, reposition the original ones to give evenly spaced support.

Establish by how much you need to lift the guttering at each screw position, this may mean that you have to reposition the brackets higher than they were originally fitted.
If you have not removed the affected section of guttering, put a couple of strong nails into the fascia about 25mm (1 in) below the gutter to support it while it is being refitted. Take out the old fixing screws and rest the guttering on the support nails. If you need to re use the original, worn, screw holes, tap wall plugs into them for added security. Lift the gutter up to the required height with bits of timber placed under it onto the support nails, and resecure the brackets using new screws. Finally, remove the pieces of wood under the guttering, the support nails and the string line.

Corrosion and cracks on metal guttering
Inspect cast iron and steel systems for any signs of rust and clean back with a wire brush. Then treat any bare metal areas with a rust killer. Fill hairline cracks with two coats of rust primer. Fill definite cracks or holes internally with a piece aluminium fixed across the crack/hole with non- hardening mastic. You can use a car body filler to make good the outside appearance. Rub down with fine sandpaper.

Where other types of metal are used, check for corrosion and treat appropriately for the metal in question.

Corrosion is always worst at the back edge of the gutter and to repair this you will have to dismantle the system and treat each section separately at ground level.

Cracks in plastic and cement guttering
As these systems are seldom painted, large repairs tend not to be visually worth while if replacement sections are readily available.

Leaking joints

Metal or cement
If you cannot dismantle the joint completely, only carry out repairs after a period of dry weather to ensure that any crack is completely dry internally.

Seal leaking joints internally with waterproof mastic after cleaning the surface. If you have one leaking joint, the others may also be suspect, so make a good job and apply mastic to the inside of all the joints.

If you can remove the section adjacent to the leak, clean off all the old sealant, spread fresh metal putty (or a good mastic sealant for cement) into one side of the joints and press the section into place (use nails through the bolt holes to align the sections), wipe off any excess putty with a cloth. Once the length is firmly seated, insert and tighten the bolts and wipe away any extruded putty - always use washers and do not over tighten bolts on cement guttering. Beware, however, that removing one section of old guttering, may put stress on other joints along the run and may cause these to leak.

Plastic
If a leak develops at the joints of a plastic system, release the affected joint and lift it clear of the adjoining length - you may need to also release the adjacent support bracket. If the gasket in the joint is sound, you can simply clean the gasket and the underside of the lifted section (use water with washing liquid to remove any hardened muck) and replace the section. Make sure that the sections are correctly aligned, the upper section must cover the gasket but should not be pushed hard up against any part of the joint - normally a space of about 5mm needs to be left for longitudinal expansion. If the gasket is worn, scrape away all the old material and insert a replacement gasket or apply three good strips of mastic sealer in its place. Then clip the two sections together again.

Replacing a section

If metal guttering is severely rusted you will have to replace the affected section, or even the whole system. If this is necessary, you may wish to choose a plastic system (it is cheaper and will be easier to handle than metal). However, some metal guttering has been in place for a hundred years and more, so if you can afford it, and can find a supplier, installing metal will last your lifetime. In conservation areas in the UK, you will have little option other than using original style/material for replacements.

When buying a replacement section of guttering always take along a piece of the old system to make sure you buy the shape and size. Always 'offer up' your sample alongside what you are buying, a few millimetres difference can make a new section useless so always double check. The ogee section is fairly standard as are the sizes of round guttering. Take care when buying replacement plastic sections that you choose a range with the same method of sealing as the rest of your system. It is always a good idea to fit new gaskets when fitting a new length, so don't forget to buy some.

Metal gutters and pipes are heavy so get someone to help you fit the new section.
Uncoupling old joints on metal/cement systems is often easier said than done since the bolts are likely to be rusted solid. Use a hacksaw or angle grinder to cut off the bottom of the screw and nut. Be very careful when releasing old metal/cement guttering from the fascia, one minute the section will be supported by the brackets/adjacent sections, the next minute you'll be taking its full weight. If you are at the top of a ladder, you need to be properly balanced when you have to take the weight. Force the sections apart and remove the old section. Scrape off the old sealing material in the joint. Clean up and treat any rust spots on the adjoining sections of metal guttering.

With the old length at ground level, compare its length with the new piece (hopefully the new piece will be the same length or slightly longer). If necessary, cut the new piece to length.

The new section of guttering may have pre-drilled holes at each end to take the bolts. If not, or if you needed to cut down the new piece, support the gutter on a thick piece of wood laid on a flat surface and drill the hole(s) from the inside where required. If your new metal guttering is not ready-painted, apply a rust-resistant primer inside and out before fitting it.

Spread fresh metal putty (or a good mastic sealant for cement) into one side of each joint and press the section into place (use nails through the bolt holes to align the sections), wipe off any excess putty with a cloth. Once the new length is firmly seated, insert and tighten the bolts and wipe away any extruded putty - always use washers and do not over tighten bolts on cement guttering. Beware, that replacing one section of old guttering, may put stress of other joints along the run and may cause those to leak.

Plastic

Although plastic is considerably lighter than metal guttering, long length of plastic can be awkward to handle at the top of a ladder, so consider your safety (and anyone at ground level) when working at the top of a ladder.

Remove the section to be replaced, normally this is just a matter of unclipping it as necessary. With the old length at ground level, compare its length with the new piece (hopefully the new piece will be the same length or slightly longer). If necessary, cut the new piece to length; clean the cut edge using sandpaper or a fine file.
Clean or replace the sealing gaskets, position the new length in place, make sure there is adequate clearance at each end of the new section for expansion and secure it using the supporting brackets and finally the end sealing clips.

Painting guttering

Metal
Metal guttering should be well painted for protection. If the outside of the guttering has previously been painted, just rub it down, apply metal primer to any exposed metal and then under and top coat it. Normal gloss paint is adequate. For the inside of the gutter, check to see if it has previously been treated with bituminous paint. To do this, apply a little white gloss to a small area in the gutter. If the gloss turns brown after a couple of hours, the coating is bituminous and it is probably better to apply a fresh coat of bitumen paint rather that try to paint it. If the inside of the guttering is not bituminous, you can apply normal metal primer (if not previously painted), undercoat and top coat - this is an ideal place to use up any leftover gloss paint from other jobs as only the birds will see it.

Cement and plastic
It is not a good idea to paint either cement or plastic guttering.