I Sandset Flagstone Patio


Lagstones make a great, long-lasting patio surface with a naturally rough texture and a perfectly imperfect look and finish. Randomly shaped stones are especially suited to patios with curved borders, but they can also be cut to form straight lines. Your patio will appear more at home in your landscape if the flagstones you choose are of the same stone species as other stones in the area. For example, if your gravel paths and walls are made from a local buff limestone, look for the same material in limestone flags.

Flagstones usually come in large slabs, sold as flagstone, or in smaller pieces (typically 16" or smaller), sold as steppe/’s. You can make a patio out of either. Larger stones will make a solid patio with a more even surface, but the bigger ones can require three strong people to position, and large stones are hard to cut and fit tightly. If your soil drains well and is stable, flagstones can be laid on nothing more than a layer of sand. I lowever, if you have unstable clay soil that becomes soft when wet, start with a four- inch-thick foundation of compactable grave] under your sand.

There are a few different options for filling the spaces between flagstones. One popular treatment is to plant them with low-growing perennials suited to crevice culture. For best results, use sand-based soil between flagstones when planting. Also, stick to very small plants that can withstand foot traffic. Another option is to create a rock garden effect by eliminating an occasional small flag in an out-of-the-way spot and planting the space with a sturdy accent species. If you prefer not to have a planted patio, simply fill the joints with sand or fine gravel—just be sure to add

Landscape fabric under your sand base to discourage weed growth.

The following project includes steps for building a classic flagstone patio. You’ll also find instructions for building low dry stone walls, the ultimate add-on to a stone patio surface. If you’re new to working with natural stone, see pages 177 to 179 for some basic cutting tips.

Tools & Materials ►

Mason’s string

Stiff-bristle brush

Line level

Circular saw’ with

Rope or hose

Masonry blade

Excavation tools

Plugs or seeds for

Spud bar

Ground cover


Eye and ear



Marking paint

Work gloves

1" (outside

-/4" plywood

Diameter) pipe

V/" deck screwrs

Coarse sand

Pointing chisel

Straight 2×4

Pitching chisel


Stone chisel

Spray bottle

Hand maul

Stone edging

Dust mask

Sand-based soil or

Chalk or a crayon

Joint sand

Square-nose spade

Lumber (2×2,

Crushed stone





Mason’s 1 rowel


Adding a Stone Wall ►

A dry stone wall is a simple, beautiful addition to a flagstone patio. A wall functions as extra seating, a place to set plants, or extra countertop or tabletop space. It also provides visual definition to your outdoor space.

See page 182 for how to build a stone wall.

Lay flagstones so their tops are approximately 1/2 to 1" above the surrounding ground. Because natural stones are not uniform in thickness, you will need to adjust sand or dirt beneath each flagstone, as needed.

Gaps filled with sand-based soil, sand, or gravel

Backfill with sand

Optional compacted gravel: 4 to 6"



A typical sandset patio has a layer of coarse sand for embedding the flagstones. A sub-base of compactable gravel is an option for improved stability and drainage. The joints between stones can be filled with sand, gravel, or soil and plants. Edging material is optional.

Flagstones that are

Cut into rectangular shapes can be laid in square or rectangular patterns with uniform gaps.



Outline the patio base using string and stakes for straight lines and/or a rope or hose for curves. The base should extend at least 2 to 4" beyond the edges of the flagstones, except where the patio will butt up to a wall. Transfer the outline to the ground with marking paint. Remove any sod and vegetation within the base area.

Set up layout strings to guide the excavation using stakes or batterboards (see pages 38 to 41 for detailed steps on layout and site preparation). Excavate the base to a depth of 2" plus the stone thickness plus ‘h to 1". Slope the ground away from the house foundation at a rate of Vi" per ft.






Lay sections of 1" pipe across the project area to serve as screed gauges. These allow you to strike off sand at a consistent depth when you drag a screed board over them. Note: Since large flagstones can be held in place adequately by the surrounding soil, edging for the patio is optional; it often looks best to allow neighboring ground cover to grow up to the edges of the stones. If you do plan to use edging, install it now.

Fill the site with coarse sand slightly above the screed gauges. With a helper, drag a straight 2×4 across the screed gauges to level off the sand. Use a screed board that’s long enough so that you can avoid stepping in the sand. Work the screed in a back-and-forth sawing motion. Remove the pipes once each section is finished, fill in the voids, and smooth the surface flat.



Arrange your flagstones into groups according to size and shape. As a general rule, start paving with the broadest stones and fill in around them with increasingly smaller pieces, but appearance and sight lines are also important: If there is one nice stone with a flat surface and good color, feature it in the center of the patio. Or, if some of the patio will be visible from the house, choose nicer stones for these areas.

Begin by laying large, thick stones around the perimeter of the patio. Leave a consistent gap of about 1" between stones by matching pieces like a puzzle and cutting and dressing stones as needed (see pages 177 to 179). The outer edge of the patio should form smooth curves (or straight lines) without jutting pieces or abrupt irregularities. Level stones as needed by prying up with a spud bar and adding or removing sand underneath.


Fill in around the larger stones with smaller pieces cut to fit the spaces, as needed, working from the outside in. After setting a band of stones a few courses wide, lay a 2 x 4 across the stones to make sure they’re level with one another. Add or remove sand below to adjust their height and dampen the sand occasionally to make it easier to work with.

Fill the joints between stones with sand-based, weed — seed-free soil (see page 231). Sweep the soil across the patio surface to fill the cracks, and then water the soil so it settles. Repeat as needed until the soil reaches the desired level.

Plant plugs or seeds for ground cover to grow up between the stones, if desired.

Sand-based soil (also called "patio planting" soil) is the best material to use for planting between flagstones. This mixture of soil and sand sweeps easily into joints, and it resists tight compaction to promote healthy plant growth, as well as surface drainage. Regular soil can become too compacted for effective planting and drainage and soil from your yard will undoubtedly contain weeds. Sand — based soil is available in bulk or by the bag and is often custom-mixed at most large garden centers.

As for the best plants to use, listed below are a few species that tend to do well in a patio application. Ask a local supplier what works best for your climate.

Alyssum Rock cress Thrift

Miniature dianthus




Patio "planting soil" (for planting between stones) is available in bulk or bags at most garden centers. It is good for filling cracks because the sand base makes it dry and smooth enough to sweep into cracks, yet the black compost will support plant growth. Because it is bagged, you can be assured it doesn’t come with weeds.

Updated: 16.05.2013 — 18:42
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