I hope you're ready to dig! It's time to start preparing a flagstone walkway site. Put on your boots, gloves, safety glasses and get a little dirty if you are doing the excavating yourself. This is the start of physical labor.
Let's go over a few things first, like having a permit (if one was required). You should also have your utilities marked, and have your base marked with landscape marking paint.
As with any project with a sub-base, try to hit a clay base or very hard packed dirt. This is called the subsoil. If you have dug down 8 or 10 inches for your recommended depth and it is still soft, keep digging to see if you can hit a more solid base. You may be only a few inches away from clay.
If you are, then excavate the rest out as well. Its better to start from a good hard subsoil base than trying to pack in soft soil. Gravel is usually pretty cheap, and more is better.
If you don't reach a hard enough clay base, then we recommend a jumping jack for subsoil compaction.
It is also important to plan your sub-base according to adjustments around your project. You may be raising it for soil, sod, or drainage reasons. If you are raising your walkway higher than existing ground levels, then subtract that from your excavation amount. This may be tough if you have soft soil and you may just have to add more gravel to your requirements.
If you have to get rid of a lawn, than I suggest you rent a sod cutter to remove the grass first. You can rent these at most rental centres. (Make sure you are clear on how to use it before leaving the rental store).
A sod cutter will peel up the grass, and a little bit of dirt and roots. This will save you a lot of time trying to dig through the sod. Also, keeping sod and dirt separate will save some of you dumping fees for separating clean fill (like I do).
Have some ribbon and stakes handy to mark off your excavation area, as well as someone to put utility marks or flags back exactly where they were before you excavated.
If you have someone excavate your area for you with heavy equipment, be careful if you are building over any marked utilities. Make sure they know where they are. This is especially important if you have shallow in-ground irrigation, phone, cable, and electrical lines. Gas lines are usually down further, but it is always better to be safe than sorry.
It's also a good idea to use a square nosed shovel and dig your perimeters out first as an excavation guide. This helps prevent the bordering lawn from being torn by bobcat or skidsteer buckets. (This is a pain in the butt to repair.)
The perimeter should also be excavated a few inches wider than the planned walkway size. Your gravel sub-base support needs to extend a little further than the edge of the stone. Four to six inches is plenty, and if you need to plant grass up to the edge you can clean a bit of this gravel out later after your edging is spiked in.
This perimeter is a "Ledge" that will have to support the type of edging you will be installing.
Leveling and Staking
Small tripod laser leveling is great if you know how to use them. Drive your stakes into the ground around the walkway area (6 to 8 ft or so apart). Leave about 2 or 2 ½ feet sticking out of the ground. Use your laser level and shoot the beam along the stakes. Mark a line on each stake. (This will be considered the level mark for all stakes) you should be able to eyeball the high end and the low end already.
When you have all your marks on your stakes you should start planning how and where you are going to drain water off the surface.
This is achieved by running a grade. A grade of 1 inch off a 3 ft wide walkway is normal. You will need to decide which side you want the water to drain to. Add 1 inch to the mark on the opposite side that you will be draining water from.
On the stake at the lowest end, mark where you want the top of your walkway to be. You can now dig down from here 2 inches for the stone, 2 inches for the sand, and the required sub-base depth of gravel for your region.
Let's say for example that your sub-base requirement was 6 inches. You will be excavating down from the top of the walkway mark, 6 inches, plus 2 inches for the sand, plus 2 inches for the average thickness of stone (10 inches in total). To do this on all stakes, use a tape measure and measure down from the level mark you made on all the stakes.
Below is a video on using a laser level. Although this is prep work for a concrete base, the principles of usage and theory of finding the slope apply to our application with a flagstone walkway.
String levels are another cheap and easy way to determine any grade and set your excavation requirements. Tightly tie some string to 2 stakes at each end of where the walkway will be and place the string level on the string. The string should be just above the ground or grass along the length of the walkway.
Have someone move the string up or down at the low end while you watch the bubble. You can mark on them a LEVEL mark when the bubble is level. Repeat this step from the first stake to all other stakes until you have consistent coverage of marked stakes along the walkway.
To make sure you are excavating to the correct depth, use string between the stakes and measure down from the string accordingly. It may be a pain in the butt leaving the string up during the excavation process. Take it down and use it only as a guide when needed.
Unlike a brick or interlock walkway with consistently thick bricks, a flagstone walkway does not require a screed bed to start from. The thickness of the stones can vary an inch or so in thickness, and you will have to adjust the sand or crushed rock base frequently to allow for this.
You are also going to be preparing any transition zones along with the walkway area. Make sure you are preparing for transition zones as you are excavating for the walkway.
For example, If you are lining the walkway with garden beds, excavate what you need to at the same time you do the walkway. this will save you from possibly damaging the walkway or edging doing it after the walkway is done. Proper planning and sequencing saves time and money.
Happy digging! Now let's talk about preparing the base.