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Tuesday, 26 October 2010 14:05

Digging holes - options, tools, tips and tricks

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fence postsIf you're building a fence the old fashioned way, you'll need to dig holes. Even with a tractor and rammer there will be times you need to resort to putting a post in manually.

There are a few options for making a hole, and some tips and techniques to go with them:

Spade

Best to use a "Fencing Spade" designed for digging postholes - they're long handled, just the right weight, with a blade shaped for lifting dirt out of the hole. Even though you might be putting a round post in the ground - dig a square hole.

Hand rammer

Steel pipe with a shaped weight on one end. Used for compacting soil back in around the post.

Two-handled posthole shovel or scoop

A tool with two handles, two blades - works with a scissor action. You can cut a perfectly round hole and scoop out debris with the same tool. Enables you to dig a hole with little if any bending.

Hand tools - including breaker bars and chisels

For digging in rocky or very hard ground - use a breaker bar in conjunction with a spade or scoop. The TERRAX® with its reaction bar (invented and made in NZ) is a brilliant tool when dealing with hard and stony soils.

Hand borer or auger

Good workout for the abs. Use a spade to remove a square of turf before using a hand borer.

Petrol borer or auger

Available as one or two man machines. Great if you've got a lot of holes to do, not a good idea in stony ground or near to trees/tree roots. Can be hired at all good hire centres as an alternative to owning one.

Tractor or machine mounted augers

A really good option if you're planning a lot of post hole boring. If you already have the tractor they're cheaper to buy than a tractor mounted post rammer. Also an option on tractors too small to mount a post rammer on. Can be hired at all good hire centres as an alternative to owning one.

Specialist equipment for impossible situations

If putting the fence somewhere else isn't an option - consult a specialist or contractor. Fences can be put anywhere - you're only limited by your wallet. Excavators with breakers or augers, rock drills, blasting, or building fences completely above ground (e.g. stone walls) are among the options when everything else fails.

Digging Tips:

  • Don't dig holes any bigger than you need them to be
  • Mark the desired hole depth on your spade or a measuring stick
  • Keep the dirt from the hole as close to the hole as you can and in a tidy pile. After all - you are going to be putting it back in the hole around the post
  • Dig the face or "wire" side of the hole straight and in line with the line of the fence
  • Check the hole is the right depth before you drop the post into it - to save you having to lift it back out again
  • The post should go hard up against the face of the hole - meaning you only have to compact soil on three sides of the post rather than all four

Ramming

  • Soil should go back into the hole around the post in the same layers it came out - i.e. soil from the bottom of the hole goes back at the bottom of the hole
  • Line your post up in the hole and start with approx 250mm of soil around the bottom of the post
  • Hand ram the soil (good and hard) to compact this down to about 125mm and check post for plumb/straightness
  • Shovel another 250mm of loose soil into hole and compact again, check for plumb/straightness again
  • Shovel enough soil in to come halfway up remaining hole and repeat ramming and checking
  • The final layer needs to be real tight - to keep water out and make the post nice and strong in the hole
  • You are allowed to use concrete around a post, but hand rammed soil is much cheaper and just as strong in most situations

Ramming Tips:

  • Hold the rammer vertical and close to your body
  • With your forearms parallel to the ground, hold the rammer handle with your hands close together
  • Breathe in > lift, breathe out > thump
  • Don't hit your feet
  • Don't hit the top of the post with your fingers