How to Install a Gutter: Slope, Fixings and Fittings Explained Step by Step

A badly installed gutter causes overflows, leaks and facades that gradually deteriorate. The good news: installing a PVC gutter is within the reach of a competent DIYer, provided you respect two fundamental rules. The first is a sufficient slope so that water flows naturally towards the downpipe. The second is a regular spacing of the brackets so that the profile never sags under the weight of the water. Here is how to do it right first time, with the correct measurements and techniques.

The materials you need

• Half-round or square PVC gutter (diameter 100 or 125 mm depending on the roof area)
• Brackets or fixings: roughly one every 60 to 80 cm
• Downpipe outlet, bends and downpipe matching the profile
• PVC gutter adhesive, or push-fit fittings with a sealing gasket
• Chalk line, tape measure, pencil, hacksaw or miter saw
• Stable ladder or scaffolding and a safety harness if the roof is high

Choosing the diameter matters: a 100 mm gutter is enough for a small roof, but a large roof area, a steeply pitched roof or a very rainy region justifies the 125 mm. If in doubt, take the size up: a gutter that is too small overflows quickly during storms, while a larger diameter costs little more.

Calculating the gutter slope

The slope is the one thing that guarantees water flows to the downpipe. The usual rule of thumb is 1 cm of fall for every 3 to 5 metres of length, i.e. roughly 2 to 3 millimetres per metre. Concretely: for an 8-metre gutter, the highest point must be placed 2 to 3 cm higher than the downpipe. A slope that is too steep, beyond 5 mm per metre, makes water spill over the front edge during heavy rain, because the water does not have time to reach the bottom of the profile. A flat or reversed slope, on the other hand, lets water stagnate, which freezes in winter and cracks the gutter.

Marking and positioning the brackets

1. Locate the high point near the end opposite the downpipe and the low point 1 or 2 cm below the drip edge
2. Stretch a chalk line between the two points to mark out the slope line
3. Mark the position of each bracket in pencil every 60 to 80 cm
4. Screw the brackets in along the line, checking the spacing with a level
5. Tighten each bracket so that the edge of the gutter aligns with the chalk line slope
6. Check the complete line before clipping the profile into place

Installing the gutter and the fittings

1. Cut the lengths with a hacksaw at a slight angle, then deburr the cuts with a file
2. Clip the first length into the brackets, with the bottom of the profile towards the back
3. Join the lengths together with a connector: PVC adhesive or sealing gasket depending on the model
4. Fit the downpipe outlet at the position of the low point, towards the inside
5. Connect the bends and the downpipe, then fix the pipe to the wall with clips every 1.5 m
6. Pour water into the gutter at several points to check the flow

The downpipe must discharge either into a drainage gully, into a rainwater tank, or onto the ground with a bend that carries water away from the foundation. A downpipe that empties straight against the house wall causes rising damp in the foundations. Fitting a leaf guard at the top of the downpipe also prevents blockages from leaves, especially near trees.

The mistakes to avoid

• Flat or reversed slope: water stagnates and overflowing is guaranteed in winter
• Brackets spaced more than 80 cm apart, which make the gutter sag under the weight of the water
• Gluing all the fittings without respecting the drying time stated on the tube
• Running the pipe down too close to the ground: water splashes onto the facade at high flow rates
• Fixing the brackets into a rotten or poorly anchored support that gives way under the load

Maintenance after installation

A new gutter must be cleaned at least once a year, ideally after the leaves fall in autumn. Remove the debris by hand or with a jet of water, check that the bends are not blocked and check the hold of each bracket. Take the opportunity to unblock the downpipe outlets, which clog up first. With a good annual clean and a correct slope, a PVC gutter lasts twenty years without any other intervention.

Installing your gutter is above all a matter of method: careful marking out, a regular slope and fixings spaced at the right distance. By following these steps, your facades will stay dry and your roof protected for years, and you will save the cost of a professional while keeping the satisfaction of a job well done.