A flagstone pavement not only is durable and solid, but if properly constructed, it can last forever. For many people this lasting quality far outweighs the fact that flagstone is a relatively expensive paving material.
There are many different types and colors of flagstone to choose from. The colors are subdued-yellow, brownish red, gray, buff-any of which adds a mellow warmth to the garden floor. The shape is either irregular or rectangular, the latter costing more because of the expense involved in cutting. Some types of flagstone can easily be cut on the job, with a wide chisel or simply by breaking over the edge of a 2 by 4 (the latter is more risky because it often doesn’t produce a straight cut). Thicknesses vary from ½ inch to 3 inches. A 2-inch thickness is required if you want to pave over a sand bed; a 1-inch thickness is ample for paving over a concrete slab.
SETTING FLAGSTONES IN SOIL
One of the easiest ways to lay thick flagstone paving is to place the stone directly on the soil. If the area to be paved has good drainage and is not too large, this method is quite satisfactory. The stones may shift and settle slightly during wet weather, but they still provide a good footing.
A more permanent method for setting flagstones in soil is to first remove the soil to a depth of slightly less than the thickness of the stones. Then fit the stones in place, adjusting the soil to fit the underneath contours of each piece.
SETTING FLAGSTONES IN SAND
The method for laying flagstones in sand is essentially the same as used for bricks but has two main differences: (1) After the bed of sand has been laid and thoroughly screeded, set the stones in place, working them down until they are well imbedded. (2) Lay all the stones before filling in the joints, so that you can study the effect of the pattern and make adjustments accordingly.
Once you have achieved the pattern you desire, fill in the joints with soil. Do this carefully so that the soil is not flush with the surface of the stones. Then wet the area thoroughly with a fine spray.
SETTING FLAGS ON CONCRETE
This method requires that the flagstones be bedded in a layer of mortar spread over a permanent base of concrete at least 3 inches thick. It also requires that you try out your pattern as described above before setting the stones permanently in place.
Use a wet but not soupy mix of 1 part cement to 3 parts sand and spread it on the concrete base in small areas, covering just enough to place one or two stones. Then while the mortar bed is still damp, lay the stones in place and firmly tamp them down using a trowel handle. Use a straightedge to check for level.
Allow the stones to set for at least 24 hours. Then fill in the joints with grout (a mixture of 1 part cement, 3 parts sand, and 1/s part lime or fireclay) and smooth the surface with a pointed trowel. Before the grout dries, wipe off any excess mortar with a clean, damp cloth.
CASTING CONCRETE FLAGSTONES
You can obtain pleasing results by casting imitation flagstone paving in concrete. Not only is this method less expensive than buying real flags, but it allows you to produce the exact effect that you desire in color, pattern, and texture.
To cover a large area with cast concrete flagstones you will need to build a wooden grid form that will make several stones at one filling . The inner surfaces should be smooth and slightly flared out toward the bottom for easy removal after the concrete sets up slightly.
Before you begin, thoroughly soak the form with water. Greasing or oiling the inside of the form with soap or engine oil will help prevent the cement from adhering to the wood. Put the form down on soil that has been graded and tamped level and fill each compartment with concrete. After it has set slightly, remove the framework, smooth the edges of the blocks, and set up again for the next section of paving. Let the castings set for 24 hours before moving them and handle them gently for three weeks.
You can also cast individual concrete flagstones for stepping stones in a simple wooden form or in a dirt mold right where they are going to be laid. Make a form with 2 by 4’s, nailing two corners together, hinging the second and third, and putting a hook on the fourth . Place the form over building paper, oil it, and pour in concrete that has been mixed 1 part cement, 2 parts sand, and 3 parts gravel. When the concrete has set up slightly, remove the form and smooth off any rough edges with a trowel. Clean the form, re-oil, and refill with concrete. Keep the completed blocks damp for three days.
The easiest method for making stepping stones is to pour concrete right in depressions in the ground where you want them. Remove the soil for each stepping stone to a depth of 4 inches and fill with the same concrete mixture as described above. Use a wood float to trowel the surface smooth, and keep it damp for 3 days. If the stones are cast in a lawn, the surface of the stones should be slightly below the lawn so a mower can easily pass over them.