Understanding Windpost Connections at Gable Ends

Wind posts are vertical steel columns built into masonry walls to carry lateral (horizontal) wind loads. They are particularly common at gable ends, where the wall rises above ceiling level and cannot rely on the roof for intermediate support.

At the top of the windpost, the lateral force must be transferred into the floor or roof structure. How this connection is made at gable end walls depends on whether there is a floor joist running parallel to the wall or perpendicular to it.

The Common Problem at Gable Ends

At the gable end of a building, floor joists typically run parallel to the gable wall — they span between front and rear, not side to side. This means there is no joist spanning perpendicular to the wall that the windpost can simply tie into.

The Accepted Connection Method

Where rafters or joists run parallel to the gable wall, the windpost connection is made using a mild steel restraint strap fixed to the side of the nearest parallel joist, running horizontally across to the windpost.

To make this connection robust:

1. Install noggins (short blocking pieces of the same timber as the joists) between the joists at the connection point. These stiffen the local area and provide a solid bearing surface so the strap fixing location doesn’t flex under load.
2. Fix the mild steel restraint strap from the windpost top, running horizontally over the noggins and screwing into the side of the parallel joist and/or the noggins.
3. The strap transfers the horizontal load from the windpost head into the floor diaphragm, which then distributes the load to the main structure.

Typical Specification

– Strap: mild steel, minimum 30 mm × 5 mm section, or a proprietary restraint strap of equivalent capacity
– Fixings: appropriate structural screws into timber (minimum 50 mm penetration)
– Noggins: same depth as the floor joists, at 400–600 mm centres around the connection point

When Further Engineering Is Needed

This connection method handles standard domestic wind loads. If the windpost carries unusually high lateral loads (e.g. a very tall gable or a large opening below), the restraint strap size and number of fixings should be verified by the structural engineer.

Raise a Change Request or contact us if the gable height or opening sizes are unusual for your project.