How to install and care for flagstone in your hardscape

There are many ways to drastically change the look and feel of your front and backyard without undergoing a major overhaul. A simple yet drastic upgrade is incorporating flagstone into your hardscape.

Flagstone is a flat, hard stone that usually consists of sandstone combined with binding materials such as calcite, silica, and iron ore. It is cut into flat slabs that are often used to line walkways, patios, and other features. Its shades of red, blue, and buff enhance the natural elements of the outdoors.

Fun fact: Ash Fork, Arizona, is the flagstone capital of the world!

Ordering and installing

Flagstone is an incredibly durable material that can last centuries when properly maintained. It is also something a DIY enthusiast can install themselves, though it is time-consuming. One of the few drawbacks of installing flagstone yourself is the sheer weight of the stone. Be sure to have a few helping hands and wear a back brace and closed-toe shoes during the installation.

Ordering: Order at least 25% more stone than the project requires. Here’s why:

• Even when taken from the same quarry, stones taken from a deeper level or slightly different area may result in mismatched colors. A larger quantity ensures there will be alternatives available on site without reordering.

• The stones are irregularly shaped and are pieced together into a mosaic. You need to ensure there are good stones left as the end of the installation approaches.

• When laying thin veneer flagstone over a concrete slab, the pieces are more prone to cracking or even breaking.

Installing: As the Landscaping Network explains, flagstone can be laid on a dry bed of sand and gravel or mortared to an existing concrete slab.

Dry-laying flagstone in sand: Dry-laid flagstone means the flagstone pieces are placed on a bed of sand and gravel. It is recommended that a patio or walkway base be at least 3 inches deep, then filled with a layer of compacted gravel covered with coarse sand. Place the flagstones in the desired pattern, starting at the perimeter, and work inward. Large stones should be strategically placed at doorway entrances or the bottom of steps to ensure stability in heavy-trafficked areas. Once the stones are placed, the joints can be filled with sand, planted with groundcover, or mortared.

Mortared flagstone: Mortared flagstone is pieces that have been permanently set with mortar to a prepared subbase. This can be more expensive to install.

Wet mortar is applied directly on a subbase of compacted gravel and sand, or to an existing concrete slab. The flagstones are placed in the bed of mortar and then the joints are filled with sand or additional mortar or colored grout.

• Start with a reinforced concrete base that has a proper slope for drainage.

• Pressure wash each piece of flagstone to provide a clean surface for a good bond.

• Each piece is fitted and mortared to the concrete with a mixture of cement, sand, and water.

• You can use a color additive to the mortar for setting the base and the grout joints between the stones.

Be mindful that the stones themselves can vary in thickness. Therefore, the ground will need to be leveled to different depths to ensure a smooth top layer.

A note about sealing: It may be tempting to seal the flagstone to protect it from the elements. However, this is not a good idea. As it sits in the hot sun, sealed flagstone will likely deteriorate and discolor at a faster rate due to the moisture trapped underneath the stone. Talk to your contractor or salesperson before sealing the flagstone.

Maintenance

Like everything else, flagstone requires regular care and maintenance to keep it looking like new. Both installation methods will require readjustments of the stone. Because the slabs will settle over time, they may need to be shifted back into place.

Cleaning: Sweep flagstone regularly to prevent dirt and plant debris from staining. If spot cleaning stains or mold is required, bleach or muriatic acid diluted with water can be used. Mix one part bleach or muriatic acid (not both) to 10 parts water. Wear gloves and protective eyewear. You may also use a cleaner developed specifically for flagstone. Grease and rust stains will require harsher chemicals. Many home improvement stores will carry this type of product. Read the product’s label before applying.

Landscaping Network notes that when chemicals, especially acids, are used to clean flagstone, they should be rinsed off as soon as possible to prevent damage. If you have a large expanse of flagstone that needs cleaning, hire a professional crew.

Ask your contractor or the stone salesperson how to care for your stone type and installation method before buying cleaning products or mixing a cleaning solution.

Repairing: Repairing flagstone can be just as easy as maintaining it. Because the stone is laid in pieces, stones that have cracked or broken can be replaced one at a time without having to tear up the entire patio. If a stone cracks, scratches, or stains, the affected piece can simply be replaced instead of having to redo the entire patio. Additionally, if stones are installed without mortar shift, they can be lifted, and more sand added to the space beneath. For mortared flagstone that has been damaged by freeze and thaw cycles, re-grouting may be necessary. This involves removing the failing mortar with a chisel or screwdriver and replacing it with fresh mortar.

Other considerations

Be sure to wear shoes or at least flip-flops when walking on flagstone. Flagstone reflects the sun and can get very hot. It also gets slippery if wet.

Flagstone works well in different climates and doesn’t expand and contract when the weather changes.

A flagstone patio can last many lifetimes if taken care of properly. This is especially important if your property will be handed down through the generations.

Join Rosie on the House every Saturday morning from 8 a.m. to 11 a.m. on KTAR News 92.3 FM. If you’d like to send us questions or comments, email mailto:info@rosieonthehouse.com. Follow us on Twitter and “Like” us on Facebook. For more do-it-yourself tips, go to rosieonthehouse.com. An Arizona home building and remodeling industry expert since 1988, Rosie Romero is the host of the syndicated Saturday morning Rosie on the House radio program. Call 888-767-4348 with questions and comments.