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Roof Gutters

Installing PVC Roof Gutters

Roof gutters (or troughing in the UK) are channels that are installed around the lower edges of roofs to collect rainwater and carry it away to downpipes and from there to ground drains.

Roof gutters come in semi circular, ornamental or square shapes, the square ones are often called box gutters. Early roof gutters were often made from wood or cast iron, these days gutters are usually made from PVC, aluminium or zinc alume coated steel.

An Enquiry about Box Gutters

I received an email from a pleasant man who was seeking box gutters.

Box gutters were originally made from wood with a metal lining and were noted for leaking either from poor joints or from rusting of the galvanised steel lining. The wood quickly rotted once the lining leaked.

Aluminium Box Gutters

In Australia these days box gutters are made from aluminium and are the most widely used roof gutters. They are often shaped on site using rollers and formed from aluminium strip. These gutters have a row of slots along the outer side so that if the downpipes block and the gutter overflows the water will escape outwards rather than running inwards under the roof and onto the soffits (that outside ceiling under the eaves).

PVC Roof Gutters

In Indonesia roof gutters (known here as Talang) are a fairly new innovation for general use. Two sections are available, a half round version and a square section which, to all intents and purposes, are box gutters. Both are made from PVC and fittings are available and each comes in 2 sizes. The round gutters are to be avoided, they are not strong and the steel brackets they come with are simply not up to the job.

The square section gutters are good, they come in 15cms and 20cms wide and with a range of fittings such as connectors, right angles, end pieces and downpipe connectors.

Installing roof gutters

They are easy to assemble using a hacksaw to cut and solvent cement to connect (do not use PVC glue, make sure it is solvent cement or the connectors will leak).

Very good PVC brackets are available for the square section gutters. You will need to watch the people installing the gutter closely. The fact that water runs downhill is a magical quality little understood by the average "Butter" whose highly developed skills in the recycling of cigarette ends have rendered him eminently suited to his vocation as a master plumber.

It is well to remember that water is heavy stuff and when a gutter gets full there is a lot of weight to hold up, surprisingly a fact that is lost on an average labourer. You need to use plenty of brackets, probably at least one every 60 cms of gutter length.

Joints must be well made or they will leak so great care must be taken with cleaning and applying the solvent cement to the joints.

Gutters must be installed very straight but with a slope towards the end where the downpipe is. To do this a string should be used to make sure the brackets are all dead in line before the gutter is installed. A clear piece of plastic tubing with water in it is used to check the levels from one end of the gutter to the other. A 2% slope is very effective. The gutter clips into the PVC brackets and does not need any other fixing if it is installed correctly.

Poor Installation

If the gutter has wavy sides along its length you know that the people installing it have not got it straight enough and the gutter may “pop out” of the brackets.

A very common problem is that a gutter will be bowed in the middle, of course water will collect and the weight may well make the gutter bow even more and even overflow. Better quality gutters have overflow slots in them to make sure that if they overflow the water runs away from the building and not into the roof space.

Fascia boards along the edge of roofs may not be installed vertically, they are usually at right angles to the slope of the roof and so it is difficult to install a gutter which should always be mounted square to the ground. If you are building a new building try and insist that the fascia boards are installed vertically so the gutter brackets can be easily installed. You may find resistance to this from builders or architects who simply don’t understand what you want to do or how to achieve it.

Square PVC gutters and the fittings are widely available from building and hardware shops.

Copyright © Phil Wilson April 2013
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