How to Install an Urban Bluestone Patio

In this video, This Old House landscape contractor Roger Cook helps a homeowner install a bluestone patio in an urban backyard.

Steps for Installing a Bluestone Patio

1. Call the utility company to confirm that there aren’t any buried cables, wires, or pipes in the patio area.
2. Use a shovel to remove all the topsoil, exposing the undisturbed subsoil.
3. If you uncover a buried cable or pipe, encase it in sand, then lightly compact the sand with a hand tamper.
4. Spread 3 to 4 inches of graded base across the area. (Graded base, or pack material, contains ¾-inch stone and stone dust.)
5. Rake the base smooth, then firmly compact it with a gas-powered plate compactor. Run the compactor in two directions, first across the length of the patio, then across its width.
6. Cover any buried cables or pipes with caution tape, then cover the tape with graded base.
7. Add another 3 to 4 inches of graded base and compact it again. Repeat until reaching the proper grade.
8. If a concrete footing protrudes into the patio area, chip away the concrete using the electric rotary hammer.
9. Install a series of wood stakes and nylon strings to establish the height of the patio. Pitch the string down about ¼ inch per foot from the house, to ensure the patio will drain water away.
10. Make a setting base for the bluestone by mixing in a wheelbarrow 9 parts stone dust, 1 part Portland cement, and a little water. Mix the ingredients with a shovel.
11. Shovel some setting base onto the patio and smooth it with the brick trowel.
12. Set a bluestone slab into place and tap it down with a rubber mallet.
13. Add more setting base and set the next bluestone slab. Insert ½-inch-thick shims between the slabs.
14. Drive metal ground stakes into the ground against the sides and ends of the slabs to hold them in place.
15. After completing the first row of bluestone slabs, set the second row, making sure to stagger the joints between the slabs.
16. Once all the bluestone slabs have been tapped down, remove the metal ground stakes, and pour polymeric sand into the ½-inch-wide joints between the slabs.
17. Use a push broom to sweep the sand into each and every joint.
18. Sweep away all the excess sand, then use a garden hose to spray a light mist of water over the entire patio.
19. Wait five minutes, then spray the patio again.

Technique Detail: Bluestone is naturally bumpy, so it’s important to keep it as even as possible to avoid creating a trip hazard. Check the stones with a level as you go; while they may not always read perfectly level, you’ll be able to tell if they’re flush with one another and graded properly. Set all the large stones first, placing smaller stones only for reference, and don’t walk on the stones until they’re all in place.

Base-Building Detail: Depending on size and weight, bluestone slabs will settle into the wet setting mix half an inch or more, so spread the mix thicker than its planned final thickness. Check the bed thickness by measuring the distance between it and the string line. For 1½-inch-thick stones, that distance should be roughly 1 inch, to allow for about ½ inch of settling. Add or remove mix as needed to meet the finish grade.

Materials

• Kneepads
• Nylon string
• Metal ground stakes
• Push broom

Tools