By Ryan Sarvis
So you want to build a retaining wall in your yard? There are many things to consider, including the type of stone, size of the wall, size of the footings, drainage, and the need for permitting, to name a few. Here are the steps homeowners and contractors can take together to build a long lasting, aesthetically pleasing retaining wall.
Carderock: Locally Sourced Stone
There are a variety of materials to choose from when deciding to build a retaining wall. We in Maryland have an advantage because some of the best natural stone available is quarried in our own backyard. Carderock is quarried and processed locally in Potomac, MD near River Road and Seven Locks Road.
The advantage of using our native stone is that the color, texture, and size vary, and no two stones are the same. The blues, grays, browns, and greens in the Carderock ages gracefully in any setting. The classic appeal of Carderock conveys strength and beauty unmatched by none.
Picking the Right Type of Wall to Build
There are two types of retaining walls that can be built with Carderock, dry stack and veneered walls. A dry stack wall is one where we do not use mortar to adhere the stones together. The stone used is usually flat so it stacks better. However, many of our customers’ favorite walls are built with veneer stone.
The process for building a veneer wall starts with excavation for a “footing” or base of the wall. The size of the footing will grow depending on the height of the wall; however, it is important to check local building codes and permitting requirements prior to building the footers. At Johnson’s, we always expect our walls to meet or exceed local codes and regulations. Our footings, for example, typically are reinforced concrete with rebar to tie the wall and footing together.
Next, we build an 8″ cinderblock wall on top of the footing. At the time of the block wall’s construction we install 1-2″ pvc pipe passing through the wall for the drainage system. We then take the veneer stone and our expertly trained stonemasons “work the stone” for the best face and corners of the stone. High strength mortar is used to adhere the stone to the block wall. The purpose of working the stone is to have a final product that has small joints between the stone for a seamless appearance.
The top of the wall can be given a natural cap. A natural cap is a finished cap that matches the face of the wall, only with larger stones. By far our customer’s favorite type of cap is flagstone. For the best appearance, a thick Pennsylvania Blue Flagstone can be installed. These caps will hang the wall’s face by an inch, and add a great finish to the wall.
Fighting Hydrostatic Pressure
The biggest enemy of retaining walls no matter the material is the natural elements. Water is the most destructive of them all. Hydrostatic pressure is the force exerted by water behind a wall that pushes on it. A properly constructed wall with correct “backfilling” is a wall will last many generations. When the construction of the wall is near completion, a drainage system is installed behind it. This system has three main components – a perforated pipe, gravel backfill, and landscaping fabric.
The pipe is used to collect and direct water away from the wall. The gravel offers free movement of water behind the wall, therefore reducing the hydrostatic pressure. The landscape fabric is used to isolate the gravel from the existing soil and ensure that the drain pipe runs clear and does not become choked with silt in the future. Also, any excess water that does not enter the pipe travels down and passes through the pvc weep holes and exits at ground level in the front of the wall.
Through training and experience of our stonemasonry crews bring a passion for the highest quality product to your project. Our crews’ produce some of the most enduring and beautiful retaining walls in the area.