What are Strainer Posts?

Strainer posts serve as the strong anchoring points at the ends, corners, and direction changes of fences, bearing both vertical and horizontal loads to keep wires tight and maintain fence integrity.
 
If a strainer post fails, the overall stability of the fence is compromised, making proper installation critical.

Common Strainer Post Materials

Strainer posts can be made from timber, steel, concrete, or even alternative materials like composite or pipe. Pipe and concrete offer greater resistance against termites, fire, and corrosion compared to traditional timber. Steel strainer posts, once installed, require very little maintenance and can last for decades. 

Installation Guidelines

Install strainer posts at the beginning and end of fence lines, at corners, and wherever there’s a change in direction or topography.

• Depth: To handle strong forces, strainer posts must be buried deep into the soil, often with structural support like breast blocks or stays for extra rigidity.
• Stay Length: As a general rule, the stay (support pole) should be at least 2.5 times the height of the fence (e.g., a 1.2m fence should have a stay of about 3m).
• Ground Rules: Some fencing experts recommend placing half of the strainer post underground for maximum sturdiness.
• Placement Intervals: On longer fences (e.g., beside roadways), strainers are usually set every 90 meters, while posts might be spaced every 3 metres.

Proper installation of strainer posts is essential to building a long-lasting and stable fence. Contrary to common assumptions, the diameter of the post is less important than how deeply it is installed and the installation method chosen; driving the post into the ground is preferable to digging a hole and backfilling, as driven posts disturb the soil less and have a higher holding capacity. For optimal strength, ensure the post is set as deep as possible, with a depth of at least one meter recommended, as deeper posts better resist both vertical and horizontal loads — indeed, a post set at one meter has about double the load capacity of one set at only 750 millimeters.

Once the strainer post is driven or set firmly, the next step is to add a stay for support, typically at an angle that starts three-quarters of the way up from ground level on the strainer post. The length of the stay should be at least two and a half times the height of the fence; for example, a 1.2-meter high fence should have a stay of roughly 3 meters, to properly distribute the forces exerted by the fence wires and prevent strainer movement. Maintaining the correct angle of the stay is crucial, as too steep or too shallow an angle can act as a fulcrum and increase post movement, undermining fence integrity. Additionally, using a diagonal stay assembly provides not only the required strength, but also ease and speed of installation, along with adjustability for future tensioning. When assembling the stay, using a “floating” footplate on top of the ground — not pinned or buried — ensures that the stay can move slightly with the ground without transferring excessive stress to the strainer post, while also reducing installation labor.
 
Finally, always install a tension cable with diagonal stay assemblies, as this component efficiently redirects the load to the base of the strainer post, reducing both the risk of the post lifting out and the likelihood of the footplate sinking. End assemblies should be positioned wherever there is a change in fence direction, variations in the terrain, or at every gateway, to guarantee the stability of the entire fence line.

By following these guidelines — using strong, correctly installed posts, the proper length and placement of stays, tension cables, and adjustable assemblies — you’ll ensure that your strainer posts remain strong and secure for many years.