If you have some aging sandstone walls in your garden, then you may want to add some reinforcement to them. Reinforcing walls means that you can prolong the life of your walls, keeping them upright for longer. The best way to ensure that sandstone walls don't start to warp, or to fall down, is to use a concrete section, and build the sandstone around this. If you don't have this option, and need to reinforce some already existing sandstone walls, then you can do this, although the end result will not be as secure.
Step 1 - Supporting with Backfill
One of the best ways that you can support a sandstone wall is to cover one of the sides with soil, creating a hill which you can then use to grow plants or grass on. This kind of retaining wall ensures that there is enough solidity to hold up the wall. Begin by digging a hole around the base of your sandstone wall on the side that you want to retain. You can use large rocks at the base of this hole, or fill it with gravel. Take the soil which you removed from the hole, and place this on top of the gravel, so that it is pressed against the wall. Use extra soil on top of the backfill until the top of the wall is reached.
Step 2 - Create a Concrete Frame
You can also use a concrete support in order to keep the sandstone walls upright. Start by digging a hole, as before, and then add gravel to the base. You will then need to construct a frame for the concrete, in order to support it as it dries. Make this frame out of some lumber, nailing it together until you have a three sided shape. Use a tape measure to make a shape which has one long side, the length of the piece of wall you wish to support, and two short sides which will hold it against the wall. Put one of the open ends into the hole you dug, and press the shorter ends against the wall. Use a spirit level to ensure that the frame is flat.
Step 3 - Pour the Concrete
You can then begin to pour the concrete. Make up a concrete mix, and then pour it into the top of the mixture. Level off the mixture with a pallet knife, and then leave it to dry. As the concrete dries, it should bind with the sandstone walls to create a solid support for your walls. Once the sandstone has dried, you can remove the frame, and possibly use it again if more of the wall needs reinforcing.
Step 4 - Finishing the Concrete
Once the concrete has dried, remove the frame, and use a sander to polish the sides of the concrete, You can then decorate it with stones or pottery in order to create an appealing accessory to your garden.