How to install PVC guttering systems

As heavy downpours now occur with increasing regularity, it’s wise to never underestimate the importance of installing a well-fitted PVC guttering system. Correctly fitted around the roof perimeter and securely fastened to the fascias, good quality guttering and downpipes can be a first line of property defence during rainy periods, guarding against leaks and standing water issues.

By understanding how to choose a system with the appropriate flow-rate, and fitting both the guttering and downpipe so the system works cohesively, you’ll be rewarded with a installation that will serve to prevent building damage and last for many years to come.

New Projects

First and foremost - for all installations, preparation is key! Select a PVC guttering system that meets the design flowrate or area of your particular roof. As well as normal levels of rainwater, a domestic or light commercial eaves gutter system must be able to cope with intense rainfall lasting at least two minutes. Visit British Standard BS12056 and you’ll see how to work out the amount of rainwater (in litres per second) that could run off your roof.

Replacement projects

Again, consider the preparation and remember to plan your installation using specific component diagrams to assist in selecting the correct materials from the start. When it comes to replacing PVC guttering, it’s only natural to consider “like for like” as the most sensible option. However, you should consider the greater frequency of storms and increased rainfall we now experience and modify your system’s capacity as a positive precautionary measure.

Follow the guidelines and help your project to run smoothly

The below step-by-step guide has been designed to help you understand the installation process and get the best results:

Gutter installation guidelines

• Position the running outlet accurately by holding a plumb line against the fascia directly over the drain. Mark the position on the fascia with a pencil. Fit the outlet no more than 50mm below the level of the roof tiles, then fix with 2 x 25mm x 5mm round-head stainless steel screws (don’t use countersunk screws as these can be over torqued with cordless drivers, consequently damaging mouldings).
• Fit a fascia bracket just below the top of the fascia board at one end of the run of guttering (opposite end of the outlet).
• Tie a plumb line (string) around the base of the bracket and stretch from the bracket along the fascia board before tying it to the outlet.
• Check that there is a fall towards the outlet (1:350 is recommended) to encourage water to drain efficiently.
• Mark the position of the fascia brackets, spacing them according to the gutter system chosen (see table below) but no more than 150mm from any corner, union, running outlet or stopend.
• In locations where heavy snowfall is prevalent, we recommend that fixing centres for fascia brackets be reduced to 600mm.
• Fix the fascia brackets with 25mm x 5mm stainless steel screws – we would recommend using all available fixing holes. 
• Starting at the outlet, fit the first length of gutter by tilting the gutter to fit under the back clip, and clip in at the front edge. 
• Fit a union bracket at the other end of the first length and screw it into the fascia using all available fixing holes - then fit the next length of gutter into it. Continue joining lengths ensuring all joints line up with the “fit to here” depth marked in the fittings.
• Cut the last section of gutter to fit using a hacksaw and fit a stopend.
• RECOMMENDED: Use lubricant/silicone spray on all gutter seals for ease of fitting and for improved in-service performance.

The fascia bracket spacing guide below also provides some helpful information:

Once the guttering is in place, you’re ready to add the downpipe.

Downpipe Installation guidelines

• Using a plumb line, mark a vertical line on the wall from the running outlet to the drain.
• Place an offset bend onto the base of the running outlet. Place a second offset bend on a length of downpipe and measure the section length required to join the two offset bends, cut a suitable length of downpipe – the “swan neck”.
• Hold a downpipe clip centrally over the plumb line and mark the fixing holes on the wall with a pencil. Repeat down the wall, spacing pipe clips no more than 1.8m apart.
• Drill the fixing holes.
• Working from the top downwards, install the downpipe. If additional lengths of downpipe are required, join using a socket and pipe clip.
• Leave a 10mm gap between the end of the pipe and the bottom of the pipe socket to allow for expansion. Fix a pipe clip over the joint.
• Use wall plugs suitable for the substrate and when fitting pipe clip screws to ensure that the application is secure. Fix pipe/socket clips with 2 x 32mm x 6.5mm round head stainless steel screws.

Where required, fit a shoe at the bottom of the downpipe so that it directs water into the drain, if required. Fix the joint with a pipe clip.

Hopefully, these technical pointers will enable you to better understand the PVC guttering system installation process and help you to get the job done right, first time.