Calculate dimensions of gutters


If the gutter is too small, water can constantly spill over and cause expensive damage to the facade. Therefore, you should carefully calculate the dimensions of the gutter. This also includes the diameter of the matching downpipe.

Diameter of the gutter must fit

The diameter of the new gutter must match the roof surface to ensure reliable drainage. The area can be halved in the calculation, if the gutter on both sides gets a drain.

Which gutter diameter for which roof size?

To the matching gutter always includes a downpipe in the appropriate size. The following list gives first the diameter of the gutter and then the downpipe diameter.

If you have a roof surface that is even larger than about 160 square meters, it is advisable to use other processes to be able to hold the water reliably, even during a downpour.

  • Roof surface up to 25 square meters - 70/50 mm
  • Roof surface up to 50 square meters - 100/70 mm
  • Roof surface up to 100 square meters - 125/100 mm
  • Roof surface up to 160 square meters - 150/100 mm

Lengths of gutter pieces

The individual pieces of the gutter are usually available from one to four meters. For a gutter made of metal you should shop as accurately as possible, with a plastic gutter that is not necessary because it can be cut very easily.

In addition to the slope of the gutter you must also calculate any expansions by heat. Both are certainly completely irrelevant in a short piece, but makes on a great length but a few inches.

Do not combine different pieces to achieve length

Even if it is still so tempting to combine an old metal gutter with a new plastic gutter to save some money. The different materials such as plastic and metal for gutters you do not get really drip-free in the long run together.

The different materials do not work in the same way with temperature fluctuations and the joint will therefore be constantly exposed to high loads.

Tips & Tricks

With a large roof surface, two or more drains are a good guarantee for draining the water. There is a lot of work involved, as the drainpipes eventually want to be buried, but the positive effect is enormous at the same time.


Video Board: Gutters CT: Commercial Size vs Standard Size (for Homes)