Flagstones are close-grained sedimentary rocks that can be quarried in layers giving them a flat appearance. They are usually a group of related rocks instead of a specific rock, almost always containing quartz and mica. Flagstone walls have been used by centuries and have many uses ranging from creating raised flowerbeds to building decorative fencing to facing a home. There are many different kinds of flagstones to use in building.
There are several different types of flagstones you can use when building a wall. Some flagstones absorb water readily making it sponge-like, while others repel water making them slippery. Flagstones are mostly easily recognized by their rugged, natural appearance, but they come in different finishes as well. Some of the basic types of flagstones are limestone, quartzite, bluestone and sandstone. Different finishes, such as flamed, honed, polished and sandblasted tend to change the appearance, texture and color of the natural stone. Cost can depend on which type of stone is quarried near the buyer, and how far the stone has traveled to get to the building site, usually starting at $200 to $500 per ton. Imported stones can become more pricey, and uneven and randomly shaped stones are usually less expensive.
Color depends on the basic material used in the sedimentary process. Flagstones made from sandstone can be found in different colors of gray, red, white and yellow. Limestone can have impurities such as clay, sand and organic materials and is usually found in gray and tan. Bluestone is primarily found in gray and vibrant bluetones and varieties in between, and quartzite flagstones are often found in white and lighter colors, but in different parts of the world can be found in blues, blacks, coppers and greens as well.
If possible visit the quarry before you begin building. If the quarry is far away, obtain samples, but don't rely on photos to choose your colors and textures, or you may not be happy with the product you receive.
Building Your Wall
Building a flagstone wall seems easy enough but is time consuming and labor intensive. First lay out the area and draw the dimensions, including height, to take to the quarry or hardscape store where a knowledgeable salesperson can tell exactly how much flagstone is needed, and what types of flagstones are offered.
While waiting for delivery or before you lay the first flagstone, dig a 10-inch deep trench below the wall and fill this with gravel to make a level place to lay the flagstones. This is not required, but a level surface is needed, so if you choose not to do this you may need to remove or fill in places to make the surface completely level.
Using the largest flagstones first, build your wall in layers overlapping the flagstones to avoid a vertical seam. Set evenly shaped stones aside for the top layer to make it appear uniform, and smoother. Staggering the flagstones towards the fill dirt at a rate of one inch per foot of height gives the wall more stability. While not required, mortaring the top layer of flagstones on the wall gives the wall stability and lengthens the life of the wall.
Put the top pieces out to see which way they fit best before applying the mortar, and keep in mind you might need smaller pieces to fill in gaps. You may choose to mortar the entire wall for the most durability possible, or choose to pack the gaps in the wall with dirt for durability. Packing with dirt can give a more rustic look in time because grass or plants can grow in these places.
Basics To Building a Wall
Flagstones are relatively easy to work with since they are a flat stone. To make smaller stones to fill in gaps, you may need to cut or break the flagstones. Breaking flagstones to make a straight edge is fairly simple. Using a chisel to score both sides of the stone then place the stone on the scoreline over a piece of wood or other work surface and using a sledge to break away the unwanted part. Take care to use gloves and safety goggles when doing this to prevent injury.
History of Flagstones
The history of flagstone use goes back at least to the 14th century when flagstones were used as flooring in castles and other building structures in Europe. In the United States, early settlers used flagstones for building fireplaces and fences, as well as for use as grave markers for loved ones. Small farming communities became large towns practically overnight with the discovery of flagstone in the ground. Quarries would employ hundreds of workers to dig the quarries, cut the flagstone, haul flagstone and other related jobs, such as bootmakers to repair the workers' shoes or teachers to run a one room school house.
The work was very labor intensive with only steam engined shovels to dig for flagstone, and cutting the flagstone was done with hand saws. Nowadays, flagstone quarries are in many regions of the United States and all over the world, making it one of the most readily available building stones known.
Things to Consider
When choosing to build a flagstone wall you will need to consider other costs besides the flagstones themselves. Some of these costs are: mortar, gravel if you choose to use this method, fill dirt if using the wall for raised beds, special tools for breaking the stones if you decide to do so, or special cutting tools. Also consider the type of flagstone you want, and what is available in your area opposed to what would need to be special ordered. Keep in mind the absorbency of different stones. If you want to be able to sit on the edge of your finished wall, you might not want to choose a stone that will absorb and hold water.