Shophouse Outdoor Unit Rattles: Bracket Never Sat Flush

A bracket on aged brickwork that works loose repeatedly, in an airwell that funnels wind straight against the unit. Each retightening holds for a while and then gives way. The brickwork surface is visibly uneven.

Repeated loosening after apparently sound work points at how the bracket meets the wall rather than at the fixings themselves. A bracket bearing on high spots contacts the wall at two or three points instead of across its face, so it rocks about those points under load. Every rocking cycle works the fixings a little further, and the wind funnelling through the airwell supplies plenty of cycles.

A bracket transfers load to a wall through whatever it actually touches. On an uneven surface that is a few high points, so the load is concentrated and the bracket can pivot about them. Wind pushing on the unit rocks it about those contacts repeatedly, and each cycle works the fixings a little further. Tightening harder simply increases the pressure on the same few points rather than creating any new contact.

The bearing surface is made good so the bracket meets the wall across its whole face, using packing or a levelled bed rather than more force. Once the load is spread, the fixings stop being worked and stay tight. This is worth getting right at installation on any old or uneven wall, because the alternative is a mounting that is retightened indefinitely.