Post Fix & Concrete

Post fix & concrete is essential for the fast setting of wooden, concrete and metal fence posts.

Post fix, also known as post mix, is a high quality compound that has already been mixed for you. Being pre-mixed means you don't have to embark on the time consuming and sometimes complicated task of measuring and mixing cement and ballast; also being bagged makes it easy to transport to the site and even through the house if need be.

Post Mix

When using post mix, position the post vertically in the hole and if happy with its position half fill the hole with water then pour the mix evenly around the post. The amount of post mix required would depend on the size of the hole the post is going into, but would recommend the top of the concrete stopped 50mm from ground level.

After two minutes, check the vertical position of the post with a spirit level, front and side faces, and adjust as necessary. Allow 15 - 20 minutes for initial set to take place, prior to commencing with further work.

Most fence posts require one-two bags per hole for a typical timber fence post. However, if you are filling a bigger hole for a larger fence or gate post, more post mix will be required.

Here at AVS we sell a handy 20 kg bag of post fix, which has been manufactured from fine aggregate.

Concrete is traditionally mixed from Ballast and Cement on site, giving a more economical way of making concrete giving the ability to adjust the strength if need be.

postmix instructions

How many bags of Post Fix do I need?

Post Shape & Size Hole Size (Width x Depth) Approx number of bags needed
Round 2" (50mm) 6" (150mm) x 12" (300mm) 1/2 Bag
6" (150mm) x 18" (450mm) 1/2 Bag
6" (150mm) x 24" (600mm) 3/4 Bag
8" (200mm) x 12" (300mm) 2/3 Bag
8" (200mm) x 18" (450mm) 1 Bag
8" (200mm) x 24" (600mm) 1 1/2 Bags
Square 3" (75mm) 8" (200mm) x 18" (450mm) 3/4 Bag
8" (200mm) x 24" (600mm) 1 Bag
8" (200mm) x 30" (750mm) 1 1/3 Bag
12" (300mm) x 18" (450mm) 2 1/4
12" (300mm) x 24" (600mm) 3 Bags
12" (300mm) x 30" (750mm) 3 3/4 Bags
Square 4" (100mm) 8" (200mm) x 18" (450mm) 2/3 Bag
8" (200mm) x 24" (600mm) 3/4 Bag
8" (200mm) x 30" (750mm) 1 Bags
12" (300mm) x 18" (450mm) 2 Bags
12" (300mm) x 24" (600mm) 2 3/4 Bags
12" (300mm) x 30" (750mm) 3 1/2 Bags


When mixing your own concrete on site the general mix for fence posts would be 6:1, 6 of ballast to 1 of cement. Mixing can take place in a wheelbarrow for ease or sometimes on a board.

Depending on the ground conditions, once mixed and the post is in its correct position; the concrete can be poured into the hole dry and rammed down, or used wet and (once all air pockets removed from concrete) the post should be supported until set.

More economical than Post Mix, but less convenient.

concrete in fence post