If you're building a flagstone walkway or patio, it's important to know how to adjust the stones so they are level. Uneven surfaces pose a trip hazard and take away from the appeal of your landscape. The most effective way to level flagstone is to build a strong, level base with edging to keep the stones from shifting in the first place.
Excavate the site where you plan to lay flagstones to a depth of 8 inches, or below the frost line if your area gets freezing temperatures in winter. Building a deep foundation prevents frost-heave damage from dislodging the flagstones.
Install wood or metal edging on all sides of the patio or walkway. Drive 10-inch nail spikes through the edging to attach it firmly to the ground.
Spread 6 inches of crushed rock over the surface and compact it with a hand tamper. Pour a 1-inch layer of course sand over the gravel and spread it even with a rake.
Place the first flagstone in a corner of the site, tapping it into the sand with a rubber mallet. The level of the first flagstone will determine the height of the entire surface. Step back and make sure the flagstone is not too high or low, and add or remove the sand as necessary.
Continue setting the flagstones according to your pattern, keeping an even spacing of about 1/8 inch between each. As you go, place a water level over the stones and tap them firmly into the sand base to level them.
Pack fine sand between the joints of the flagstones on all sides. Continue packing the sand until the spaces are completely filled. The sand joints provide cushioning and deter the flagstones from shifting as they settle.
Apply sealant over the flagstone surface to protect it from water damage and to prevent the sand joints from wearing away.
Sweep the top of each of the flagstones with a push broom using vigorous force to remove all surface debris from them.
Put on safety glasses and gloves as well as long sleeves and pants to protect yourself from the acid.
Fill a plastic bucket with a mixture of 1 part sulfuric acid to 20 parts water. Sulfuric acid is the same acid that is used to clean swimming pools and is available at hardware stores and pool supply companies.
Pour the acid over the flagstones until the surface of each stone is completely wet.
Allow the acid to sit on the flagstones for two to three minutes to begin dissolving the stains.
Scrub the surface of each flagstone vigorously with a brass, wire brush using circular motions.
Rinse the surface of the flagstones with spray from a garden hose to wash away all of the acid solution from them.
Excavate the area where you will lay the flagstones. The excavation needs to be at a depth of 3 inches for the sand base plus the depth of the flagstones. Tamp the bottom of the excavation flat.
Prepare the sand for the base. Mix one part Portland cement to three parts of builder's sand.
Water the bottom of the excavation until the soil is very wet.
Pour the sand into the excavation to a depth of 3 inches, then level the sand with a rake or by dragging a board across it.
Place the flagstones on the sand and use your hand or a mallet to tamp them into place.
Set a nozzle on a garden hose to a fine mist. Spray the mist over the flagstones for about 10 minutes so that the water washes into the cracks around the stones.
Let the flagstones sit for at least a week before walking on them. Fill the gaps with mortar made from Portland cement, sand and water mixed to a warm-peanut-butter texture. Wipe up spills and use a tuck pointing trowel to smooth the mortar between the flagstones.
Cure the mortar for several days before using the flagstones.
Using a wheelbarrow and shovel, cover your work area with screening to a height of 3 inches above grade.
Rake until the surface is smooth, the center rounded, and the sides tapered.
Tamp so the top surface is compacted to 2 inches above grade and the sides taper to 1 inch above grade.
Wash the flagstones with warm water to remove any debris, and allow them to air dry.
Mix the mortar you are working with per manufacturer's instructions, and pour it into the area where you would like to set the flagstones.
Place a flagstone at one end of the mortar-covered area, and press it down into the mixture. Sink the flagstone into the mortar until there is only a quarter of an inch protruding.
Continue to place flagstones into the mortar in this fashion, fitting the sides of each slab a 1/2 inch to 1 inch away from the previous slab.
Use a rag dipped in warm water to wipe away any mortar that might have gotten onto the tops of the flagstones during the placement process.
Allow the flagstones to set in the mortar for 48 hours before walking on the surface.
Purchase moss at a garden store or nursery, or harvest existing moss growing on your property. Moss can often be found in damp places near a faucet or along a building foundation. If you don't have moss, ask a neighbor if they are willing to share. Peel up pieces of moss with a trowel, putty knife or table knife.
Pull any weeds or grass that has grown up between your flagstones. Moisten the soil around the flagstones and the bottoms of the moss. Lay the moss on the soil between the flagstones so the roots make contact with the soil. Alternately, place a piece of cardboard over the moss and step firmly on the cardboard.
Water the moss immediately after planting, and water it every day for three weeks. After that time, the moss won't need water unless it begins to look dry or lighter in color.
Treat your flagstones with a siloxane concrete sealer. Do not use a urethane sealer because it will seal the pores of the rocks and prevent them from being able to breathe. This will cause the bricks to eventually become discolored. Siloxane only partially seals the stone, and helps prevent water, sun and oil damage. Apply sealer to a new or thoroughly cleaned patio and reapply sealer every two to three years.
Clean your patio periodically by spraying it down with a good high-pressure hose sprayer. Clean oil stains with dish soap and warm water. Keep your patio free of organic matter like leaves. If left to sit on the patio for long periods of time, organic matter can cause staining and discoloration. Use an organic stain remover to clean these stains.
Fix and repair problem areas as you see them happening. Fix loose stones by removing them and re-sanding the bed where the stones rest. For mortared patios, patch cracked or damaged mortar by chiseling out the mortar and applying new mortar with a putty knife or trowel.
Prevent large amounts of water from dumping on or pooling up on your patio. Constant water contact in one area will cause deterioration of the stone. Install gutters on the roof above the patio to divert rainwater falloff.