Triangular colony boxes

One of the ideal positions for Swift nest-boxes is high up in a gable end. Often the highest point of any house, such positions are preferred by Swifts. A triangular colony box fits well with most buildings.

Computer model superimposed
on photo of gable
We here give the detailed design of a cabinet to fit a 90° apex. Such a cabinet can be built to fit other angles (examples here), though angles other than 90° can be a little more tricky to make.

A 90° cabinet looks acceptable high up in gables with angles greater or less than 90°, they just don't fit as snuggly.

We here describe a cabinet with 6 chambers, but it could be restricted to 3 or extended to 10 chambers.

1 sheet of 12mm exterior plywood, 2440mm x1220mm - requires 2/3rds of a sheet
1 batten 25mm x 37.5mm, length 1220 to support the bottom of the front.
'3 x 2' timber (section dimensions typically 70mm x 45mm), length 1500mm, this is sliced in half at 45° to make the front battens. These battens are to produce a more interesting front, as well as to reduce intrusion of rain and light.
Triangular gussets, 6  pieces 150mm long - can be made by slicing a 25mm x 37.5mm batten at 45°
2 triangular gussets for the apex of the box.
Featherboards - 160mm x 4.5 metres - cut in to pieces 300mm long for the roof. If there are broad eaves at the top of the gable, then this is not needed.
(A simpler covering could be roofing felt or something similar that is water-proof.)
Wood treatment such as Cuprinol, Ronseal or Sadolin, only treat the exterior of the box.
35mm screws, rust-proof better for the front.
If the box faces the sun, then the front needs to be double thickness. The inside layer can made by cutting a square of ply 610mm square then cut it in half and screw the 2 pieces to the back of the triangular front. The front should then be painted white.
A strip of roofing felt to protect the very top of the cabinet.

Hints on finding a roof slope.
Invariably, the slope of a roof is a ratio involving 12 e.g. 5:12, 9:12 or even 12:9. A 45° roof is 12:12.
The first 5 triangles we have made were all different, but all a ratio involving 12. Carefully taking a photograph of the gable by pointing the camera perpendicular to the wall will produce a picture from which you can find the nearest ratio of 12. The centre point of the picture should be the same height as the camera. You can find expanded details here.

Hints on positioning the feather-boards
Feather boards are not needed if the eaves are broad enough.
It needs sufficient featherboards to provide an overlap of about 30%. One featherboard needs to be cut so that one piece supports the bottom featherboard, and the other piece finishes the top.
Featherboards provide an attractive finish, but other roof coverings in situations exposed to sun and rain can also be used. The top feather boards should be covered by something water-proof.

Dimensioned elevation (click to enlarge)

Internal layout - floor width should be about 15cm
The top is covered by a piece of angle plastic

Front view
Cabinet installed on a north-facing gable.
For a south-facing gable, the front should be painted white and possibly made of thicker plywood.

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