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Post mix concrete in a 20kg bag is a fast-setting, ready-to-use solution for securing fence posts, gate posts, and pergola posts in the ground. Simply pour into the hole and add water. Sets in 5 to 10 minutes, with posts ready to load within 30 minutes.
| Property | Detail |
|---|---|
| Material | Factory-blended, kiln-dried concrete mix |
| Bag Weight | 20kg |
| Setting Time | 5 to 10 minutes |
| Load-Bearing Time | Approximately 30 minutes |
| Suitable Post Types | Timber, metal, and concrete posts |
| Packaging | Sealed plastic bag, suitable for outdoor storage |
Dig your post hole to the recommended depth, typically one third of the post length, and ensure the hole diameter is wide enough to allow the mix to flow around the base of the post. Pour the dry post mix directly into the hole around the post, then add water slowly and evenly until the surface is saturated. Support the post plumb while the mix sets, and avoid applying load for at least 30 minutes in normal conditions. Store unused bags in a cool, dry location away from moisture, as the kiln-dried formula will begin to react if the packaging is compromised.
How many 20kg bags of post mix do I need per fence post?
For a standard 75mm x 75mm fence post in a 300mm diameter hole at 600mm depth, one 20kg bag is usually sufficient. Larger gate posts or deeper holes may require two bags. As a general guide, measure your hole volume and allow approximately 16 to 18 litres of mixed concrete per bag.
Can post mix concrete be used in wet or clay-heavy soil?
Yes, post mix concrete performs well in most UK soil types, including clay. In very wet conditions, reduce the amount of added water accordingly, as the soil moisture will contribute to the setting process. Avoid using in waterlogged holes where standing water cannot be removed, as this can dilute the mix and weaken the set.
How long should I wait before fitting fence panels after using post mix?
Posts are typically ready to take the weight of fence panels within 30 minutes in dry conditions, though full cure strength develops over 24 hours. For heavy gate posts or in cold weather below 5 degrees Celsius, allow a full 24 hours before applying any significant load.
Browse our full range of timber fence posts at Nottage Timber Merchants, available to collect from our yard in Bridgend or with next-day delivery across South Wales. Stock up on posts and post mix together to keep your fencing project moving.
