Swifts can be a difficult species to establish in artificial nest boxes. However, if you have an appropriate location, the effort is well worth while.
The nest box should be made from 12mm-15mm thick weatherproof exterior or marine ply. Cut the roof, front, back and base, and check the dimensions before cutting the side panels which fit inside the other panels. Swifts seem to like a snug, discreet entrance, so ensure the single entrance hole is cut quite accurately (60mm long x 30mm high) in either the front or the base.
Base entry may deter other bird species from using the box.
Screw (and glue) all joints. Internal batons can be used for reinforcement at each end. Do not treat the interior of the box, but the outside can be stained or painted. Roofing felt can be fixed to the roof for added protection. Bolt the box to strong rustproof brackets and fixings under the eaves, or in the apex of a gable, in the shade, well away from the sun. It should be at least 5 metres above ground, with clear adjacent airspace and no obstructions, to enable the swifts to ‘drop’ out of the nest. The nest can be cleaned out each winter, but this is not essential.