Flagstone pavers are known for their random sizes and rough, semi-flat surfaces which give them a natural look. While large flagstone pavers can be set in sand or directly on top of tamped soil, for the firmest installation it is best to lay them on a bed of mortar over a concrete slab.
Things You'll Need
- Cold chisel
- Latex-fortified thick-bed mortar
- 2x4 board
- Garden hose
Begin by placing the flagstones onto a concrete substrate. Unlike tiles, they can be arranged unevenly and pieced together like a puzzle, which can take a significant amount of time. Attempt to maintain a fairly consistent width between the pieces of stone.
Cut stones to make them fit properly, when necessary. First hold a stone in place and draw a cut line. In order to maintain the jagged edges characteristic of flagstones, cut the stone with a cold chisel and sledgehammer. Tap along the cut line to produce small indentations. Then, with the tip of the chisel on one of the score marks, strike the chisel with a sharp blow to fully split the stone.
Begin setting the stones once the entire project is dry-laid. Pour a bag of latex-fortified thick-bed mortar mix into a wheelbarrow and gradually add water while mixing with a shovel. Mix until the mortar is stiff enough to hold up a stone yet wet enough to stick to the shovel when held on the edge for a few seconds.
Begin applying the mortar one stone at a time, starting with the thickest stone of the walk or patio. Carefully pick the stone up, trowel a 1-inch-thick bed of mortar under it, smooth the mortar slightly, and set the stone in place. Repeat for all stones in the surrounding area.
Set a short piece of 2x4 on the stones and place a 2-foot level on that. Then press the stones into the mortar, making sure their surfaces wind up being relatively level in both directions, or pitched slightly with the underlying slab, for drainage.
Repeat the mortaring process for the stones adjacent to the first ones, using a proportionally thicker bed of mortar for thinner stones. If a stone is too low or high, remove the stone and apply or remove mortar as needed. Continue laying stones in groupings, gradually setting the entire field.
Allow the mortar to cure for two or three days once all stones have been set.
Fill the gaps between the stones with additional mortar. Trowel the mortar into the gaps, tamp it down and smooth it with a wet sponge. Work carefully to get as little of the mortar on the surface as possible. Allow the mortar to dry for a hour or two, and then sweep the surface lightly with a broom.
Once the mortar has completely dried, spray the entire walk with water and clean the stones with a brush. If you want a more nautral look, fill the joints with fine, crushed stone; then spray the surface, using a garden hose with the nozzle set to mist so that the finer particles settle downward.
Tips & Warnings
- While flagstones can range from one to three inches in thickness, you can save money and strain by choosing thinner stones.
- The supplier should be able to give you a general idea of how many square feet you can cover with flagstone, but it's a good idea to add about 20 percent to cover any accidental breakage.
- While rearranging stones, it is a good idea to rest often in order to avoid injuring your back.
- Tiling: The Essential Guide to Home Decoration; Cassell and Parham; 2000
- Tiling: Expert Advice to Get the Job Done Right; Garskof; 2009
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