How to Build a Flagstone Patio in Maryland & Virginia

Installing a flagstone patio transforms your outdoor living space with natural stone beauty and durability. Whether you're in Montgomery County, MD or Fairfax County, VA, proper preparation is essential for a long-lasting patio. This guide walks you through each step—from site assessment and base preparation to layout and installation—so you can understand what professional builders do to create your ideal outdoor entertaining area.

Water Considerations

One of the most important considerations with any patio is water. A patio itself is not permeable, so whenever water hits it from any source, that water is going to run. This necessitates that the water is controlled in certain areas.

When in the planning phase, a build and design team must ensure the existing downspouts of the house have proper runoff. That way, water isn’t falling onto the patio itself. All the downspouts also need to be trenched ahead of time. This deliberate and strategic diverting of water is the most important consideration before actually starting the construction phase.

Also keep in mind that patios are typically built on a very gentle slant. This drop is approximately one-quarter inch for every foot away from the house. This slant allows gravity to naturally divert water away from the patio. In this way, you can strategically push water anywhere it needs to go by manipulating how that physical slant of the patio is constructed.

While this slant is not enough to necessarily be felt while using the patio, it does play an important and necessary part in controlling water runoff.

Excavation and Subsequent Layers

After the planning stage, the next step is excavation. This typically means digging down to about eight to inches below the finish grade. After that process is complete, a stone aggregate is placed next, after which four to six inches of concrete is poured.

At this point, the project is ready for mortaring on different pieces of flagstone onto the concrete.

Getting Everything Level

One key challenge of a patio install is ensuring that everything on the patio fits together despite the irregularities in the flagstone.

• Flagstone: These pieces tend to be one to two inches thick with a fair amount of irregularities and variance in the stone.
• Mortar bed: This can be anywhere from one-half inch to one inch thick. This depends partly on how thick the flagstone is.

Edges

One way to differentiate between a quick, cheap flagstone job and a more thorough high-quality job is with the edge work. As seen in this project, the front contains a brick border, and the back edging is done in a thermal cap bluestone.

These edges or “border pieces” give the job a finished, uniform look, but they also serve a functional purpose. They prevent cracking or chipping, and on steps where people are frequently walking, they keep the flagstone pieces from coming loose.

While the flagstone pieces are irregularly shaped, the edge caps are uniform, which lends the edging that clean, uniform, finished look.

For more information about the flagstone patio created for this job or how a flagstone patio could be incorporated into your outdoor living space, please contact a representative of Design Builders, Inc.