How to Install a Flagstone Patio.





Installing a flagstone patio and steps can be easily accomplished. This investigation will not dwell on all aspects but highlight some of the salient features that may save you time or provide ideas. The tools used to build a patio and steps can be dangerous and you should know how to use them. What is presented is a dry laid technique, no concrete is used. Warning: There is a very great probability that you can become injured when installing a flagstone patio, blindness, deafness, cutting off fingers, breathing in dust that causes cancer when cutting, bleeding to death. These are all possible. Follow these steps at your own risk! The author takes NO resonsibliity for your actions. These steps may be in error or may offer incorrect guide lines, use at your own risk.


  Steps come in two forms inset and sitting on top of the ground as shown. Inset steps are quite nice and typically are perferred, but can require more area, time, and rock for the same amount of tread space as above ground steps. Additional considerations include how the path will be used, the dimensions to work with, the grade of the land, drainage,  etc. Note that snow shoveling will be easier with above ground steps. 

 Remember to begin steps from the lowest point and build steps up in elevation. The steps shown below on the left were removed, they did not start from a floor base and were to narrow.

 Depending on use I have found that steps using a two foot tread provide the best movement, don't be fooled into considering only the dimension to be covered by the steps and divide this into equal treads. Three foot tread steps are good for running up or down but are quite annoying when moving over in a leasurely walk. 

On walls you may want to keep the dimensions of the rock thickness grow with the wall height, so a 7" step might use 1 3/4 but a 3 foot wall might require foot thickmaterial.

At first you might belive that the surface of the flagstone sheets should be smooth and uniform, but consider the texture of the surface, not only does the non uniform nature of the rock add contrast to the individual sheet but, often there are varying degrees of color and over all the rock can be more pleasing to the eye. Occansionally I'll try to find flagstone pieces that have small thin exfoliating pieces that sound off when walked on, a nice touch if you like the sound.

Tools & Materials

Only a few tools are required in the installation The materials are usually simple to acquire at a quarry. To move the rock use a moving dolly shown below, although its possible to move the stone with a wheel barrow this will be clumbersome. Gloves are a must, don't skimp on gloves, I have found that the insulated gloves provide the most protection, feel good to wear because they are lined, and may last longer. But usually a pair of gloves will only last a short time before holes develop. Working with gloves that have holes is okay when cutting is done, but this can not be said when leveling. Proper eye protection is required and use ear protection too! Don't breath in the dust as you cut, use a mask. 

Items you will need: Crowbar, square, tape measure, string, rebar, retaining wall block, pea gravel, hand size slege hammer, 3/4 " narrow chisel, 2" chisel, plastic or suitable material for under the subbase, flagstone.



In preparing the area I found that pea gravel worked best, sand provides the highest degree of precision but can be a lengthly leveling process. Use about four inches of pea gravel under all sheets of flagstone. A laser level can be a big help when leveling large areas, but be sure to use one that has less than 10% error and will be accurate to less than 1/2 inch across several yards, this can be expensive and it's only used occansionally.

Cutting area

As you move across the area to be covered you will need to have a cutting area close by. Consider that each piece is moved several times before it's finally placed. Once measurements are taken the sheets of rock should only go a short distance to be cut. The cutting area will hold a bed of 4 inches of pea gravel about 3 foot square. The gravel will accumulate many shard's so it will not be suitable as a bed to lay the rock on. 

The sandstone sheets come in 1.5 to 2 ton pallets, use a thichness greater than 3/2 inches thick, preferably 1 and 3/4 up to 2 and 1/8. It can be very helpfull to partition the sheets into thickness groups. As the patio runs across a edge the pieces need to have the same thickness. This will also be the case at the top of the riser on a step. 

Preparing the work area

A border is required to hold the 4 inches of pea gravel under the sheets. A fast and easy regular sized retaining wall block is useful. As always the first brick needs to be placed below ground and must be level in all directions. Take time to install the initial brick with a great deal of care. Use a rebar on the corners and set a string as a reference. Once you have poured the gravel into the patio area at the correct depth the pea gravel must be tampered down, do not skip this step, tamper all subbase rock into place, go over the area twice. Even if you use sand be sure that this step is still taken.

 Cutting Stone

Sandstone can be quite easy to cut, then again it can be quite diffcult. It will be best if the piece to be cut does not contain checks along the edge, although these can be worked with, more often than not as the stone is being cut these checks will progress across the stone and break the sheet wasting time and money. As you move the sheets do not use a jerking motion this will lead to tendonitis. The sheets can be very heavy and akward, treat them with respect, "If one falls on you, you'll know it."

Cutting the stone is divided into five steps, determining where to cut the top, how to score, where to cut the bottom, how to break the sheet, and finally how to trim. Professionals typically use a carbide tip chisels which hold a fine cutting edge much longer than the cheaper chisels I have used. Keep you blades sharp. I use a 7 1/4 inch diamond blade for all my stone work.

 Lay the uncut sheets in the final area overlapping as necessary to achieve the desired pattern. Decide which sheet will be cut by looking for and using the lines in the given sheet. Typically where two sheets meet  both will be cut, try to maintain and use the curves as these offer pleasing lines to the typically orthogonal grid like matrix that develops. 

Place the sheet to be cut under the sheet that will abut it. Use small blocks under the oppsite corner on the top sheet so that its about level as shown in the photo above. Now with a pencil run a line on the bottom sheet keeping the pencil against the top sheet. The line will end up about 1/8 of a inch away from the top sheet edge, this is about right.


The photo above shows the pencil line, its best to be able to draw multiple lines per sheet so that movement of the sheet is kept to a minimum. Use chalk to record the top of the of the sheet 

Move the sheet to the cutting area. Using your circular saw score the sheet along the pencil line, cut about 1/8 inch into the sheet. Now turn the sheet on its side and score the sides, be sure this is done. When the sheet is on its side stand on one end and look down the cut just made.

Now with one eye looking at the cut just made use your other eye to guide the pencil on the other side of the sheet. This is a key step that must be mastered, the cuts on either side of the sheet must match up to allow a clean break. in the picture below there is a small pencil line drawn (on the right photo) from the cut mark made as shown on the left photo. So the sequence is put the flagstone sheets on top of one another, make the lower sheet, cut along the mark, turn the sheet on its side and look down the sheet with one eye while drawing the mirror mark on the other side of the sheet, then cut that mark, follow up with cross cut teeth to make corrections.


 Now with all necessary sides scored place the sheet on a flat bed of cutting gravel and make sure the sheet is supported everywhere without pockets and about level. Using your chisel strike all score lines turning the sheet over as necessary. Strike holding the chesil perpendicular to the sheet at thepoint of impact. Unaligned score lines will require an excessive number of strikes. The thicker the sheet the more strikes. Make sure the sheet is supported and do not put anything on the sheet as you strike it.

I use a chisel with protection pad ring so I can say that I've never hit my hand. But I've hit the pad ring many times. After striking once or more around use a angled strike as shown below. But be careful and use a limited number of these strikes, since these can have unexpected consequences, you may split the piece incorrectly.

Very often as the sheets fit together it will become aparent that trimming is required, typically this occurs when the edge is not perpendicular and this off angle edge needs to be trimmed. One way to remove this edge with precision is to place the sheet on end and saw a sequence of kerfs into the edge, that end up looking like teeth. Then holding the sheet between your knees knock out the teeth, as shown.


The floor must run up to the first step and lie under the step, make sure the subbase is well compacted here otherwise the sheet under the first step up can settle at an angle that will be diffcult to correct. With a string set up in front of the step place corner stones first, then if the run of the step is long place corner stones at intermideate places along the run. The corner stones should be the height of the step minus the thickness of the tread sheet. 

You must remember when building outside that in most areas, "it's all about water". The area behind the step or wall must have adaquate gravel for drainage. If your step or wall blocks the flow of water then eventually the water will push the obstruction. 

After placing the corner stones fill in the first layer across the entire run of the step, or until another corner stone. Try to match heights of neighboring pieces so that cross pieces can be placed.  Do not run long vertical abutments from the bottom of the step to the tread.


 After all the stones are cut in a particular area they will need to be leveled. Start with all the stones in there proper place, then on one side or edge label the stones touching that side Row A. Call the stones touching Row A, Row B, and so on. Start by shifting all the sheets in Row B away from Row A leaving a gap of about a foot. This will leave room to work Row A to there final state. Remove Row A and tamper to proper depth, replace Row A sheet by sheet using a level on each sheet and as you go sheet to sheet, remember to provide a grade on the patio to allow rain to drain away from structures. Leveling can be very time consuming and tedious but your time will be well spent.


REV - 26MAR06 // REV A 14MAY06 //

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