Tim Doherty looks at the options and costs when it comes to managing rainfall on your roof and getting a high-quality finish

Above right: Downpipes are typically installed after the exterior finish, such as render or timber cladding, has been applied

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There’s a lot of jargon in the construction industry, which can be unhelpful for self builders. When it comes to rainwater goods and roofline choices, there are some important definitions to get your head around. So before we get too deep into the topic and specification options, let’s have a quick recap:

● Fascia board This is the vertical board at the base of your pitched roof, and is typically the section, upon which your guttering will be fixed.

● Soffit The horizontal board that closes the space between the fascia and the outside of the external wall.

● Eaves box A collective name sometimes given to the combination of the fascia and soffit.

● Barge board Where you have gabled roofs, you will frequently see a continuation of the eaves box following the angle of the gable and sitting under the verge overhang. This is the barge board. Where the barge board projects off the face of the external wall, you sometimes have a continuation of the soffit to close-off the barge against the wall, much like with the horizontal eaves treatment.

● Roofline products This refers collectively to the fascia, soffit and barge boards.

● Rainwater goods A universal term for both your guttering and your downpipes that run on the outside of the building all the way down to their termination point. More often than not, this is into a gully.

Calculating roof drainage

When choosing rainwater and roofline goods, you first need to know the area of roof surface which is to be drained. This will inform the gutter profile and downpipe sectional size required to provide the right capacity for your roof area and intended number of downpipes. Calculating the size of a given roof is straightforward: just multiply the length of the fascia by the length of the barge to get a square metre area.