Do we dry-pack our concrete post footings and then activate with water or pre mix them wet and then pour?
We typically dry-pack and then activate with water.
This debate over which way is better has really never been settled. We typically choose to dry-pack because when done this way, a very tight hole with no gaps or spaces is achieved. This is important because if pre-mixed chunky concrete is poured into a hole, drying with gaps around it, then as the soil erodes, moves and fills those gaps, you may get some movement in the post or it may start to lean. When the concrete is dry-poured then wetted, there are no gaps around the concrete between the post or the soil, which helps negate any erosion that may cause the post to lean. We care less about having a maximum PSI footing and more about having a very tightly-packed hole to keep the post level.
There is also a Fast-Setting concrete mix that can be purchased for your project. This product is meant to be dry-packed and then wetted. The directions on how to apply it is based on the engineer’s instructions on the concrete bag. This can’t be a poor-quality installation procedure if large concrete companies have products that are recommended to be installed this way.
One final reason we choose to dry-pour nearly all our footings is because we install our aluminum and vinyl fences sequentially. This means that we install a post, connect the panel and install the next post. If we wet-mixed and poured each as we went, then by the time we were done, we could not make any aesthetic adjustments with post or rail heights. Pre-mixing may also cause issues because as building and installation is taking place, it may cause the previously poured posts or footings to move. If the concrete was not completely dry, the post could move around causing a gap between the semi-dried concrete and the post.
Dry-packing as we install, allows us to make final adjustments and wet all footings at once when the fence is completely perfect and ready for our customer. We have nothing against other fence contractors who wet-mix all their footings before pouring, we just think that the benefits of dry packing outweigh that of pre-mixing. This is just our 2 cents on the matter.