(We'd like to thank these Marines and allMany fence installers advertise that they set every post in concrete. This requires that they first dig a hole. Digging conditions will dictate how effective this strategy is. There are many machines used in the fence industry to make holes. Some of them are very efficient, even in mixed rocky soil, or bedrock. Some of these machines are very pricey, and many smaller fence companies opt for augers that run off a skid loader or tractor. Others rely on post hole diggers and elbow grease.
who serve to keep us safe!)
who serve to keep us safe!)
All of these methods have a place, and in some areas of the country, setting in concrete works. Where there is a lot of moisture, and in areas that experience frost in the ground, concrete may cause more problems than it solves. Moisture transfer between wood and concrete can cause premature failure of the post due to wood rot. Frost causes more complex problems.
Frost penetration into the ground causes the dirt to close in around the concrete plug, and frost beneath the plug actually forces the plug and post up out of the ground. Some contractors try to combat this by making the bottom of the hole larger than the top of the hole, making a cone or bell shaped hole, with the goal of having a bigger foundation to hold it all down. It doesn't work as intended in most cases, because the larger surface area at the bottom of the hole offers the frost expansion a larger area to press on, and the post moves up. It also takes more concrete, (read: money), to fill the larger hole.
In areas where frost or wet conditions are a challenge to traditional post setting, driving posts into the ground has been gaining in popularity. By disturbing less ground, the installer lessens the need to haul off excess dirt, and minimizes the turf repair needed around each post. Because the post has a smaller surface area for frost to “grip”, it is less likely to move, and more likely to go back to its original position once the frost heave subsides.
Soft, wet soil is always a challenge, whether digging or driving. There simply isn't enough resistance along the sides of the post under ground to prevent it from laying over. For situations like this, and in stable soil where additional strength is called for to hang a gate or secure a corner, drive anchors can significantly strengthen the system. Modern Fence Technologies, (and others), sells a bracket that assists in connecting these driven anchors to the post. Some use angle iron “blades”, while the Modern Fence version uses 1 5/8” top rail cut offs for most smaller common post sizes as a “root”.
Driving may not be the answer to every post setting challenge, but it ought to be in every installers arsenal. Modern Fence Technologies can help you gear up for handling nearly every driving challenge. Give us a call at (888) 456-6786.