Planning and site preparation are key to a successful project. Here are some considerations for contractors when installing Unilock paving stones on a sloped property in Potomac, MD.
As always, begin with a site plan. Depending on the complexity of the project, a computer generated rendering that includes the slope of the land, will help determine the location and extent of excavation and grading. Plans also help with cost/materials calculations, as well as illustrating just how big (or small) the planned outdoor space will actually be in relation to the house and the landscape.
Careful site preparation is vital, and this is the real secret to successfully installing pavers on a sloped lot.
Site prep involves knowing the soil characteristics, properly addressing drainage, and how much soil to remove/relocate to create a level space on which to lay paver stones.
In many cases this will mean constructing retaining walls to create a level area and prevent soil and water movement that could damage the surface. Proper installation of retaining walls (including base and backfilling) is essential and will ensure the longevity of the paver surface. For extreme slopes and large-scale retaining wall projects, opt for a heavy-duty retaining wall unit, such as Concord Wall.
Proper base preparation ensures a base substantial enough to withstand the load of the pavers and foot or vehicle traffic, and prevents shifting of the pavers.
Base prep includes:
- Clearly marking all underground utility lines (electric, water, gas) before excavating/grading.
- Over-excavating the perimeter to ensure the edges of the surface have adequate support.
- Excavation depth depends on the soil conditions and the intended use of the surface.
- Poor-draining clay soil requires a layer of geo-textile, or the application of a Unilock DriveGrid before the granular base is added.
- Lay utilities before applying the base layer.
- Compact the base in 3-4” layers to ensure even compaction.
- The finished base needs to be the same level as the finished surface, with a 1-2% slope for drainage.
- Do not compact bedding sand; the sand needs to be loose enough to secure the pavers and allow for using a tamper to even out the surface.
- If you cannot finish laying the pavers in one day, avoid all foot traffic and cover the prepared surface in case of rain.
Once the site is prepared and the base laid, the area is no longer sloped. It is well-secured with retaining walls and an adequate base, and laying the pavers is the last step.
Always keep in mind that Nature has a way of moving things around. The freeze-thaw cycle can cause upheaval in paver patios IF the surface is poorly prepared and if the pavers are set too close together. Allow a small gap between pavers (⅛”) to allow for movement and drainage. Using a randomized laying pattern, such as that allowed by the various sizes of Beacon Hill Flagstone, can also help to create a surface that is more resilient under extreme conditions.
No matter how great your site prep, pay special attention to edge restraints. Unrestrained pavers will inevitably creep into the softer surrounding soil.
For homeowners, the professional installation of a hardscape on a sloped lot saves time and money, therefore opt for a Unilock Authorized Contractor. Unilock Authorized Contractors are skilled in every aspect of properly laying Unilock pavers. They also understand soil, and how to best prepare the site for its intended uses.
For contractors, visit our online Learning Center to discover the latest installation techniques of Unilock pavers and wall units.
The title image features a Beacon Hill Flagstone patio with Concord Wall retaining wall.