Fitting uPVC guttering is straightforward if the layout is right before you start fixing brackets. The two problems we most often want DIY customers to avoid are a fall running the wrong way and not giving the gutter enough support.
This guide follows Freeflow manufacturer installation guidance for the systems we stock, with the practical method we normally recommend at Wern-Wood. The same basic installation process applies to our half round guttering, square guttering and deepflow guttering.
Plan the outlet and gutter fall first
Start by marking where the downpipe and gutter outlet are going. The outlet should be positioned so the downpipe can discharge into the intended drain or gully.
Although Freeflow guttering can be installed level, the manufacturer states that fitting it with a fall increases flow capacity and reduces silting. We normally recommend using a fall for DIY installations as well. The problem with aiming for perfectly level is that level is not always truly level once it is transferred across a fascia. A deliberate fall gives you some tolerance so small variations are still more likely to drain towards the outlet rather than away from it.
Freeflow gives its best flow figures at a 1:600 gradient. To work out the fall, measure the gutter run in millimetres, divide that measurement by 600 and round up to the next full millimetre if required.
For example, a 5m run is 5,000mm. 5,000 ÷ 600 = 8.33, so we would mark a 9mm fall from the high end down towards the outlet.
1. Fix the outlet and mark the bracket line
Freeflow recommends fitting the gutter as high as practical to the roof edge, with the roof edge not projecting beyond the centre of the gutter cross-section.
Fix the outlet first. The manufacturer specifies 5mm minimum roundhead screws and says fixings should be non-corroding, such as zinc-plated or stainless steel. Once the outlet is positioned, use a string line to mark the gutter run and the required fall.
Check the direction of the fall before fixing the rest of the brackets. It is much easier to correct the string line now than after the full run has been fitted.
2. Space the gutter brackets evenly
Freeflow specifies fascia brackets at a maximum of 1m centres, with a bracket fitted within 150mm of stop ends and gutter angles. Union brackets at gutter joints must also be fixed to the fascia rather than left floating.
Treat the spacing in the same way you would fence posts: keep it even, and if you are unsure it is better to bring the supports closer together than space them further apart.
On an older mossy roof, or below overhanging trees where leaves and debris are more likely to collect, we would normally bring the brackets closer together. That gives the gutter more support if it starts carrying extra weight before it is cleaned out. Freeflow also advises that exposed, high-wind locations may require additional bracket securing.
3. Cut gutter and downpipe cleanly
All gutter and downpipe cuts should be square and any burrs removed. Freeflow recommends a fine-toothed saw.
For hand cutting, use a fine-tooth saw. If you are using a chop or mitre saw, use a blade intended for cutting plastic. Avoid aggressive wood-cutting blades because they can chip or crack uPVC. Take extra care when cutting in cold conditions, when plastic can be less forgiving.
4. Fit the gutter lengths and fittings
Start at the outlet. Freeflow's system fits by locating the rear edge of the gutter beneath the retaining lip of the fascia brackets and then pressing the front into position.
As you add gutter lengths, unions, angles and stop ends, pay attention to the insertion marks moulded into the fittings. The gutter should reach these marks so the system retains the manufacturer's allowance for thermal expansion.
Do not assume every connection needs sealant. Follow the manufacturer's instructions for the particular fitting you are using. Where Freeflow calls for sealant, use it; for example, it recommends a suitable waterproof sealant when connecting gutter adaptors to existing systems.
5. Fit the downpipe
Once the gutter run is complete, build the downpipe from the outlet. Most installations need an offset to bring the pipe back from the gutter outlet to the wall.
Freeflow says the lower offset bend should be supported directly beneath the bend with a pipe clip. Leave a 10mm expansion gap at the top of the downpipe, and fit additional pipe clips at no more than 2m intervals. Add extra clips where the pipe is likely to be knocked or otherwise subjected to impact.
If another length is required, connect it with the correct socket, fix the socket area securely to the wall and leave the same 10mm expansion allowance at the top of the additional pipe.
Finish the downpipe with the appropriate shoe into a drain or hopper, or connect it to underground drainage with the correct rainwater adaptor. See our downpipes and fittings for round and square rainwater systems.
6. Dry fit and water-test the system
Where practical, dry fit the layout before completing the job. It is a quick way to spot a missing fitting, an awkward offset or a downpipe that does not line up with the drain before everything is fixed permanently.
Once fitted, test the system with a hosepipe or a bucket of water. Freeflow's guidance says a completed rainwater installation should be tested for watertightness under working conditions.
Watch the water through the full gutter run. Check that it travels towards the outlet, that the joints remain watertight, that the gutter is properly supported and that the downpipe discharges where intended.
The two mistakes to avoid
The fall going the wrong way: mark the outlet first, calculate the fall and use a string line. Then check it again before fixing all the brackets.
Not enough support: 1m is the manufacturer's maximum bracket spacing, not a target that has to be stretched to. Keep brackets evenly spaced and bring them closer together where the roof or location is likely to put more load on the gutter.
If you are starting from scratch, shop our full guttering, downpipes and fittings range, or go directly to half round guttering, square guttering or deepflow guttering.
