The chances are you won’t realise there is anything wrong with your home’s guttering until it leaks. Note where the water is coming from, and, once the rain has stopped, get up a ladder and see what’s wrong.

The gutters on your home are supposed to capture all the ram falling on the roof and channel it to one or more downpipes. In turn these downpipes take the water into the mam drain, a storm drain, or to a soakaway in your garden. This efficient removal of rainwater is important to keep your outside walls sound. Any missing, damaged, or blocked guttering will result in water cascading down the face of your wall, leading to dampness, and eventually mortar and brick decay. You may be able to repair it: or you may be faced with having to replace whole sections or the complete system.

Until the mid-1940s most guttering was made of cast iron, although asbestos enjoyed a brief popularity. Cast iron had the disadvantage of being very heavy to work with – as you’ll find if you take some of it down. It is also prone to rusting if not properly maintained Asbestos was heavy, looked rather bulky in appearance and was easily damaged. When plastic piping and guttering was introduced, it became an obvious choice. It is light to work with, doesn’t need painting and its smooth surface allows water to flow through it more effectively In any case, cast iron is very expensive these days, and not particularly easy to obtain.


Plastic gutters come in three common sizes (measured as the width from lip to lip):

– 75mm (3in) – for extensions and outbuildings

– 100mm (4in) – for most house roofs.

– 150mm (6in) – for house roofs of very large surface area The 150mm size carries roughly seven times the volume of water that the 76mm size can take, and three times as much as the 100mm size. A CAST IRON ALTERNATIVE It is still possible to buy a new cast iron guttering in several ‘classic’ profiles as a match for existing gutters, but it’s expensive and very awkward to install.

If you want the look of cast iron you could consider hiring a specialist firm to produce seamless extruded aluminium guttering for your house.


You should check why a blockage has occurred in the first place. This may be due to sagging, or poor installation preventing a free run for the water. Or the blockage may be combined with a faulty joint which may be possible to repair. But if cast iron guttering is at all cracked it needs replacing.

If your gutter overflows during heavy rain. The chances are that it’s blocked with leaves. 9 //

You can use an old dustpan brush to clean it out, scraping the debris into piles and scooping them out with gloved hands. But prevent any bits from getting into the down-pipe or this may get blocked as well.

Coping with sags

If a section of guttering has sagged, making it lower than the top of the downpipe, the water will not drain away properly. And you will be able to see this from puddles of water collecting in the guttering itself. You must decide whether to raise the sagging section, or lower the mouth of the downpipe to bring everything back into line. If you flex cast iron guttering more than about 25mm (1 in) you’ll break the seal on the joints, causing a leak. So choose the option that involves moving the guttering least. In order to reset the guttering to the correct gradient you’ll need to fix a piece of string taut between two nails hammered into the fascia board. You can then use this as a guide as you reposition each gutter support in turn.

Leaking joints

Joints in cast iron gutters are made by over-lapping the two lengths of gutter, and bolting them together with a layer of sealant in between to form a watertight seal. As this sealant begins to deteriorate with age, the joint starts to leak.

To make the repair, first remove the bolt holding the joint together. Often this is too rusty to undo, so hacksaw off the bolt between the nut and the guttering, or drill out the rest of the bolt. Lever the joint apart with an old chisel, and scrape away all the old sealant. Clean up the joint with a wire brush, then apply a finger-thick sausage of new sealant and bolt the sections back together using a new nut and bolt and a couple of washers. Scrape off any sealant that has oozed out before giving the repair a coat of bitumen-based paint on the inside of the gutter.

Dealing with rust

If one bit of guttering has rusted right through, it won’t be long before the rest follows suit, so you may as well save yourself a lot of trouble and replace it all. If meanwhile you want a temporary repair, there are several suitable repair kits on the market. They consist of a sort of wide metal sticky tape which you apply inside the guttering and over the holes with bitumen adhesive.

Choosing a replacement

Assuming you won’t be using cast iron again – you’ll have a job getting hold of it and even more of a job putting it up, apart from the fact that it’s expensive – your choice is between aluminium and plastic. Plastic guttering is made of UPVC (unplasticised polyvinyl chloride). It’s probably the better choice for a do-it-yourself installation: it is far more widely available than aluminium, and has the edge in terms of cost and durability.

Two different cross-sections are commonly available half-round and ‘square’. The latter is often given a decoratively moulded face similar to the more ornate ogee cast iron guttering. In addition, a semi-elliptical guttering is available – it looks a bit like half-round but is deeper and more efficient. This, together with some brands of conventional profile, can be camouflaged by being boxed in with a clip-on fascia panel. Which type you choose is largely a matter of personal taste, but try to choose something that blends into the style of your home.

More important than looks is the size of the gutter. Too small, and it will be forever overflowing; too large, and you will have paid more for the installation than is necessary. It’s all to do with relating the amount of water the guttering can carry to the amount of water likely to come off the roof during a heavy rainstorm. These calculations are complicated, but you can assume that they were done when the guttering was originally installed. Just measure the existing guttering at its widest point to find its size, and buy the same again. The most commonly available sizes are 75mm (3in), 100mm (4in), 112mm (4V;?in), 125mm (5in), and 150mm (6in). If in doubt, consult the manufacturer’s literature.

The actual cross-section of the gutter may vary from brand to brand; this can make it difficult to join with existing guttering: for example, the guttering belonging to a neighbour on a semi-detached or terraced house. Most firms offer adaptors to link their product with cast iron guttering, or with a different size from within their range. However, they tend not to offer adaptors to tie in with the equivalent size from another brand, so if possible stick to one brand throughout the installation. If you have to link up with a neighbour’s gutter, find out which brand was used, and try to use the same.

There are many different fittings as well as lengths of guttering available on the market. Before you start buying your new guttering get hold of a manufacturer’s brochure from the stockist you use and carefully check to ensure you have all the fittings you will need. Make sure you understand how the particular system works before you buy anything.

Taking down old guttering

Cast iron guttering is heavy, and may also be rusted into place, so removing it can be tricky. But there is no need to be gentle with it: it doesn’t matter if it breaks. The important thing is to work in safe conditions. If you are wrenching things apart, do it in a controlled way so you don’t fall off the ladder, and so that great chunks of gutter don’t fall down. Try not to drop cast iron guttering to the ground: it shatters easily, and, if it lands on a hard surface, dangerous fragments can fly off. If you toss the guttering clear of the house you might overbalance and fall off the ladder, so aim to lower larger sections gently to the ground with a rope.

Begin with the section linking gutter and downpipe. Cut through the old bolts holding the sections together. Then, if you lift the gutter slightly, you should be able to pull it free from the downpipe. Once it’s out of the way, unmake the joints between the sections of gutter , and lift the guttering off its supporting brackets. It may, of course, be screwed directly to the fascia board.

You can now turn your attention to the brackets themselves. These are usually screwed to the fascia board just beneath the eaves of the roof, and can either be unscrewed or levered off with a claw hammer. In older houses the brackets may be screwed to the tops or sides of the roof rafters, to support the weight of the iron guttering. If there is a fascia board to which you can fit the new gutter, the ends of the brackets can be hacksawed off. Otherwise, you will have to lift off some of the roofing to remove them.

When all the old guttering has been removed, inspect the fascia board to make sure it is sound and securely fixed. If it is, fill the old screw holes and paint it before fixing the new guttering. If it isn’t, it will have to be replaced. You’ll find more information about this in another section.

Fixing new guttering

The obvious first step is to assemble the various bits and pieces you need, and you can use the old guttering system as a model to decide what’s required. It’s best to measure up the length of the guttering itself, allowing a little extra to be safe.

At the end of the run furthest from the downpipe, fix a gutter support bracket as high up the fascia as possible, and about 150mm (6in) from the end. The fixings here, and elsewhere, are made with 25mm (1 in) screws. Choose ones that are galvanised to stop them rusting. Insert a nail into the fascia board level with the bottom bracket.

At the other end of the run, 150mm from the downpipe, fix another nail, tie a length of string tightly between the two, and use a spirit level to check that this string is level. When it is, lower the second nail by the amount needed to ensure that the guttering runs downhill towards the outlet. This ‘fall’, as it’s called, varies according to the type of guttering, so check the manufacturer’s recommendations. Usually, it is in the region of 5mm for every metre of gutter run. Once you’ve found the right line for the gutter, fix another bracket level with the lowest nail.

The next job is to fix the next bracket 1m (39in) from the one at the downpipe

End of the run, using the string as a guide to set it at the correct level. Use these two brackets to support a length of gutter with the downpipe outlet attached.

Exactly how you join the gutter to the outlet or indeed make any other joins in the guttering will vary from brand to brand. With some, you slip the ends of the components into a special jointing piece called a union, and clip the whole lot together. With others, one of the components will have a union built into its end.

Now work your way along, building up the gutter run as you go and adding additional support brackets as required, again using the string as a guide. In most cases, you will need a bracket every metre, plus one on each side of every join – though some ranges contain combined unions and support brackets. Check the manufacturer’s recommendations.

The only problem you may run into is when you have to cut the guttering to length, either to go round a corner, or to finish the run with a stop end. Do the cutting on the ground using a hacksaw, making sure that you cut the end square. Any roughness left by the saw should be cleaned up with a file. If you want to turn a corner, fix the corner piece before cutting the straight piece of gutter to length. You can then use it to work out exactly how long the straight gutter length needs to be. When cutting to finish at a stop end, it is usual to leave about 50mm (2in) of gutter projecting beyond the ends of the fascia.

When you’ve finished the job and checked to see that all the joints are properly connected, take a bucket of water to the highest point of the gutter and pour it down. If the gutter doesn’t drain all the water then go back and check your work.

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