How to create the downpipe offset from a roofline in steel

60mm steel fixed Offset70 degree Bend - 2 make an Offset

The height of 2no. 70 degree bends maming a swan necThe height of 2no. 70 degree bends together to create a swan-neck offset is 240mmk is 240mm

The height of 2no. 70 degree bends together to create a swan-neck offset is 240mm


The roofline of a building, where the gutter is fitted, is commonly positioned away from the wall of he house beneath it where the downpipe needs to be attached.

The distance away from the wall varies depending on the architects design of the house.

Offsets in the steel range come in 3 options:

  • 60mm = a 'fixed' offset
  • 60-210mm = For larger projections a 'swan neck' offset can be created using 2 pipe bends and varying the angle/'twist' of the swan-neck from perpendicular (90°) to the wall
  • >210mm (anything above 210mm) = For larger projections still, an offset can be created using a cut length of pipe inserted in between the 2 pipe bends

Two 70 degree bends (i.e.GST80B70) make a ‘swan neck’ to offset the downpipe from the roofline to the wall of the building.
●   In the 80mm diameter downpipe 2 bends make a maximum of 210mm offset
●  In the 100mm diameter downpipe 2 bends make a maximum of 255mm offset

●  There is a 60mm fixed offset available in both sizes of downpipe



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●  For any other offset between 60mm and the maximums you should pivot the ‘swan neck’ inside the downpipe to whatever distance from the wall is required to meet the outlet at the roofline. So that the running outlet or prefabricated outlet is not directly above the downpipe but set off to the side as necessary.

Swan neck Bend Offset illustrated




Steel Offset Bends measures table





●  For even larger offsets, as in the case study in Aberystwyth, a cut section of downpipe can be inserted between the two bends, cut to what ever additional length is required

(N.B. remember to allow for the overlap of the swaged necks of the downpipe piece and of the the bends in your calculations).

 Swan neck Bend with a cut length between bends to make a larger Offset

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