Retaining Walls and Hardscape Features
The natural lay of the landscape tends to influence decisions our landscape architects make about retaining walls. Retaining walls and other hardscape features such as free standing garden walls, patios, steps, and walkways are used for shaping the site and finessing natural elevation changes.
Strictly speaking, a “retaining wall” is used to retain soil when it’s necessary to hold back a steep grade. However, we use walls in landscaping to achieve a variety of practical and aesthetic goals in service of the design intent. Aside from terracing slopes to create level areas on a site, we use retaining walls and freestanding walls for
- Bordering raised planting beds
- Defining outdoor rooms
- Framing views
- Establishing focal points
- Privacy and security
More Than One Way to Build a Landscaping Wall
If you are considering a landscaping project, there are two types of walls to consider: segmental retaining walls (SRWs) and masonry block walls.
1 Masonry block walls (our preferred method) require a poured concrete footer, cinder block, and natural stone veneer that is fixed to the block wall with mortar. We run rebar through the channels in the cinder block and fill them with concrete for reinforcement. The cinder block wall provides rigid structure to support the natural stone facing which is purely decorative and has no structural function.
The stone we use arrives from quarries roughly squared, but in uneven shapes and sizes. Our masons fine tune and custom fit each piece on site. Some of the locally sourced stone we like to use is Carderock, Eagle Ridge, and Oak Ridge.
2 Segmental retaining wall systems (SRWs) are manufactured wall systems consisting of interlocking concrete blocks that are vertically secured by an adhesive. The wall sits on a gravel base rather than a poured concrete footer. To maintain horizontal stability, SRWs use synthetic mesh fabric anchors called geogrids. These extend from the back of the wall and are buried in the backfill.
SRW blocks come in a variety of stock lengths so a complete system can be designed to fit site specifications. The blocks have a stone-like texture on the facing side and come in a variety of colors, textures, and styles.
Custom Built or Manufactured Wall?
The advantage of manufactured block wall systems, says Jeff Taphouse of Techo Bloc, is the speed of installation that comes from the efficiency of a complete system.
With a segmental wall system, you don’t have to wait for a poured concrete footer to dry. You can in the same day dig, pour gravel, install the base course, and build your wall. Jeff Taphouse, Techo Bloc
That speed can translate into cost savings on labor because there is no requirement for highly skilled craftsmen. The obvious advantage of custom-built retaining walls is creative freedom. In the hands of skilled stonemasons, there are no limitations on the design vision.
The choice between a custom-built retaining wall or manufactured wall system would depend on the requirements of your landscape design, the conditions in your yard, and the budget.
What to Expect When Retaining Wall Construction Begins
There will be dirt and lots of it. Whether the project is large or small, retaining wall and hardscape construction proceeds methodically through the same five phases. The first three of those construction phases require meticulous attention to detail. The beauty and longevity of your landscaping project depend on the thoroughness of your landscape construction crew. They are building a foundation to support the colorful, living landscape that will emerge at the end.
1 Site preparation. Crews create access to bring equipment onto the property, and they identify a staging area where they will store materials. They also take care of any demolition needed on site to create a blank canvas. This first phase can be shocking to some clients if, for example, we’ve torn out a section of fence and put what appears to be a road through their back yard. They know it’s part of the plan, but the reality can be a bit disorienting at first.
2 Excavation and drainage. We start shaving down the grades or filling low areas to prepare for patios. We dig trenches for subsurface infrastructure: drainage, gas and electrical lines, and wall footers. We work with our subcontractors to install pipe and run cables. After county inspection, we backfill the trenches and start building.
3 Wall building. We begin to build masonry block walls and get the sub base ready for patios and other hardscape features. Next, we set stonework and lay pavers. After we complete this phase, we are at the halfway mark.
4 Rough grading. We fill in any holes that we’ve created, fine tune grades, and add soil where beds are going to be built up. We complete the drainage system that we started earlier. At this point, the property looks exactly as it should, but there are no plants in the ground, no mulch, no sod. It’s all dirt and stone, but it looks orderly.
5 Lights, Sound, Plants. Now the transformation happens. We bury lighting and audio cables and run irrigation. We bring in plants, install lighting fixtures, mulch the beds and roll out sod. In a matter of days, we’ve taken this months-long job from hardscape desert to lush landscape.
Surprises That Don’t Surprise our Experienced Crews
Before we let you go, we wanted to mention a few challenges that sometimes occur during the early phases of hardscape construction.
- Bad fill soil. The wall footer has to be seated on native soil. This can be hard to reach sometimes because of excavation and backfilling done when the home was built. Disturbed soil is unstable. We need to dig deep enough to set the wall on a stable base so that it won’t sink over time.
- Buried tree stumps. A lot of suburban homes were built on cleared forest land. Some developers push soil over the remaining stumps. They become ours to deal with all those years later. We dig them out and dispose of them so we can pour our footers.
- Rain. If there is a high probability of rain, we don’t excavate. This may disappoint the client who is eagerly monitoring daily progress. We explain that if a trench fills with water, we have to dig out another two feet just to get the mud out. Our job managers are hyper aware of their production deadlines, but sometimes it’s wiser to be patient and catch up when construction resumes.
As we’ve shown, retaining walls are an essential part of the hardscaping portion of your landscape. Freestanding garden walls, retaining walls and borders fit together with patio areas and walkways to make a complete composition and to present the gardens and plantings at their most attractive. And this is just the beginning. As your gardens fill in and change over the seasons, your outdoor living space will only get better and more enjoyable each year.