How much water?

The gutter system must be able to drain the roof during an unusually heavy rainfall event which lasts at least two minutes.

BS12056 shows how to work out the amount of rainwater (in litres per second) that could run off a roof.

The roof area is multiplied by the amount of water running off each square metre of the roof area in litres per second.

Volume of water coming off a roof = A x B where:

A = 0.021 litres per second.

B = the effective roof area, calculated as follows:

(W+H/2) x L or L x W x Pitch factor (see table)

W = eaves to below the ridge

H = vertical height from eaves to ridge L = length of roof section

Which Gutter to Choose

Compare the result of the calculation (AxB) with the flow capacity of the Kayflow systems available. Please note the following:

1. Reduce flow rates of gutters with angles by 15%.
2. Gutter sections longer than 50 x the height of water when the gutter is full have a reduced flow rate.
3. Gutters are laid level – this can be up to 3mm fall per
4. Centrally placed outlets drain a much larger volume of

Minimum Specification for Fascia brackets

(4mm = 8 gauge, 5mm = 10 gauge, 6.5mm = 12 gauge stainless steel pan head screw)

Installation

Gutter

1. Position the running outlet accurately by holding a plumb line against the fascia directly over the Mark the position on the fascia with a pencil. Fit the outlet no more than 50mm below the level of the roof tiles. 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 and damage mouldings)
2. Fit a fascia bracket just below the top of the fascia board at one end of the run of guttering (opposite end to the outlet).
3. Tie a plumb line (string) around the base of the bracket and stretch the plumb line from the bracket along the fascia board and tie it to the outlet.
4. Check that there is a fall towards the outlet (1.350 is recommended) to encourage water to drain
5. Mark the position of the fascia brackets, spacing them according to gutter system chosen (see table above) and no more than 150mm from any corner, union, running outlet or stopend.
6. In locations where heavy snowfall is common it is recommended that fixing centres for fascia brackets is reduced to 600mm.
7. Fix the fascia brackets with 25mm x 5mm stainless pan head steel screws – we would recommend using all available fixing.
8. We recommend spraying all gaskets with silicone spray to ensure the best seal possible. This is essential for Ogee profile gutters.
9. 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.
10. 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.
11. Cut the last section of gutter to fit using a hacksaw and fit a

Downpipe

1. Using a plumb line, mark a vertical line on the wall from the running outlet to the drain.
2. Place an offset bend onto the base of the running 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”.
3. 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.
4. Drill the fixing
5. Working from the top downwards, install the downpipe. If additional lengths of downpipe are required, join using a socket and pipe clip.
6. Leave a 10mm gap between the end of the pipe and the bottom of the pipe socket to allow for Fix a pipe clip over the joint.
7. 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 5mm round head stainless steel screws.
8. Where required, fit a shoe at the bottom of the downpipe so that it directs water into the drain, if Fix the joint with a pipe clip.

RECOMMENDED: Use lubricant/silicone spray on all gutter seals for ease of fitting and for improved in-service performance.