Building a mortared retaining wall is not too difficult and can be a nice addition to your landscape. In addition, it will help prevent any erosion that might be occurring. While you can build a retaining wall out of a variety of different materials, this article will cover the steps necessary to build a natural stone retaining wall. If you plan to use brick, not all these steps will be necessary. If this is your first experience building a retaining wall, plan to keep your wall small. Walls that are higher than three feet are trickier and need more planning (not to mention permits).
Before you do any digging or planning, check with your local building codes to see if you need a permit. Normally, you will only need one if your wall is taller than three feet. Also, ask your local utility companies to mark where their lines run.
Using wooden stakes and string, layout where you plan to put the retaining wall. Use stakes that are taller than your wall will be (because you will use them to help guide you later).
Mortared retaining walls can be built using natural stone, brick, precast concrete stone, or split stone. You will need to pick out the stones in order to calculate how many you will need. Stones with round surfaces do not work well for this type of wall.
If you are using natural stone, it may be difficult to calculate exactly how much stone you need. Make sure that you are able to return any stones that you do not use. Also, it will be easier if you choose stones that have the same approximate thickness.
Laying the Foundation Layer
Dig a trench that matches the shape of your wall. The trench should be at least 1 inch deep for every 8 inches of height. In other words, if you are planning to build a 2-foot high wall, your trench should be at least 3 inches deep. When planning the width of the wall, plan on it being at least 1/4 the height of your wall.
Level the area within the trench as much as you can. Add a layer of sand or stone dust to the bottom of the trench. Then, level the layer and tamp it down.
Set aside your flattest stones for the top of the wall.
Lay the first row of stones next to the trench. This will allow you to play around with them without worrying about the mortar setting. Set some stones at right angles, it will help strengthen the wall.
Mix your mortar. A good mortar mix for this type of wall is 1 part cement to 2 parts sand. Mix while it is dry before adding water. Add enough water that the mortar will slip cleanly for the hoe. Mix only enough mortar that you can use in one hour.
Place a layer of mortar into the trench. Only place enough mortar down for a small area to prevent it from drying too quickly.
Lay the first stone in the trench. Make sure it level. Use a hammer to help level it if necessary. For best results, use the string and stakes that you laid out the foundation as your guide to keep the layers level.
Continue laying the stones down your trench. Check that each stone is level and adjust where necessary. Try to keep the wall that faces out as level as you can. Place any obstructions or rough edges toward the inside of the wall.
Building Additional Layers
Before laying down your second level rock, fill in gaps between the stones with smaller pebbles or gravel.
Brush the surface of the stones with water before adding mortar. It will help the binding.
Apply the mortar liberally to form a bed for each stone as it is added.
Try to lay each layer so that they overlap space in the lower layer. This may mean that you need to have rocks cut so that they are only 1/2 the size of the lower rocks.
After laying each stone, brush off any excess cement.
After laying each section, poke out some of the mortar from between the stones. This depth can be anywhere from 1/2 inch to 3 inches deep.
If a stone is crooked or will not fit firmly, pack some small stones around to help improve the bond.
Make sure you continue using your level to ensure that both the top and the front of the wall remains level.
If your wall is over 3 feet high, or if it is being built in an area that receives a plenty of rain, you should consider adding drainage pipes. Drainage pipes should be embedded in the wall every two feet about six inches from the ground.
Top of your wall with the layer of flat stones you set aside earlier. Some people use slate or similar type of stone as the top layer to ensure that the top is flat.
If there is space behind the wall and the hill (or other area), fill it in with dirt to help strengthen the foundation of your wall.