There are several methods to remove, replace or repair broken fence posts. Some of those methods involve buying special clamps and renting tools to drill through or pull out the concrete that holds the base of the broken post. The repairs are very effective, but each item needed adds additional cost. You can save money by using the old tried and true method of using muscle power to remove the old post and concrete base, and setting a new post in its place.
Remove the end of the fence panels that are attached to the broken fence post. Use the hammer to strike the fence panel rails from the back of the fence, or use the drill to remove the screws holding the rails to the post. Some fence builders nail the panel rails to the posts while some use screws. The rails are the horizontal boards that provide support and a place for the fence panels to attach to.
Use a 5 by 10 cm (2 by 4 inch) board to support each loose end of the fence panels. Place a board against each fence panel, then pull the bottom of the board out at an angle. Rest the angled end against the ground.
Cut the broken fence post off at the ground with the reciprocating saw. Hold the saw so that the blade is horizontal with the ground while you are cutting off the post. You can use a hand saw to cut the post off if you do not have a reciprocating saw.
Dig up the dirt around the post until you reach the concrete support. Use the sledgehammer to bust the concrete. Remove pieces that are broken out of the way. Continue to bust the concrete until you can remove all of it from the post hole.
Place the new 10 by 10 cm (4 by 4 inch), 2.4 m (8 foot) long post into the hole. The new post should be the same height as the existing fence posts. Measure from the ground up on a good post to find the height the post should be. The standard height would be 1.8 cm (6 feet) for a fence that has 1.8 by 2.4 m (6 by 8 foot) fence panels.
Add water to the 22.5 litre (5 gallon) bucket to a depth of approximately three inches. Pour in half the bag of concrete and mix the concrete into the water. Add more water and concrete a little bit at a time until you have mixed the entire bag.
Pour the concrete into the hole around the base of the fence post. Hold a level on the side of the post to straighten it. The concrete will help to keep the post in the appropriate position.
Nail a 5 by 10 cm (2 by 4 inch) board at an angle to each side of the post for a temporary brace. Place the top of a board against one side of the post and pull the bottom out at an angle. Nail the top, then rest the bottom against the ground. Repeat on the opposite side of the post with the second brace board.
Allow the concrete to dry overnight and cover the concrete with the dirt that you removed to dig out the concrete. Remove the braces from the post. Finish the job by reattaching the fence panels to the new post in the same position they were attached to the old post.
Wear safety glasses when you break up the concrete to keep fragments from hitting you in the eyes.