How to Build A Sandset Flagstone Patio Part 1 of 3

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Sandset flagstone patios blend nicely with natural landscapes. Although flagstone evokes a natural feel, the patio can appear rustic or formal. This patio has clean, well-tamped joints and straight, groomed edges along the perimeter that lends to a formal feel. Plantings in the joints or a rough, natural perimeter would give the same patio a more relaxed, rustic feel.

 

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Continue to Step 1

Overview

Flagstones 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 steppers. 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. However, if you have unstable clay soil that becomes soft when wet, start with a 4"-thick foundation of compactable gravel 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. 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 Cutting Stone for some basic cutting tips.
From: Complete Guide to Patios & Walkways, 978-1-58923-481-9

What You'll Need

Tools:

Mason’s string
Line level
Rope or hose
Excavation tools
Spud bar
Broom
Stakes
Marking paint
1" (outside diameter) pipe
Coarse sand
Straight 2 x 4
Flagstone
Spray bottle
Stone edging
Sand-based soil or joint sand
Lumber (2 x 2, 2 x 4)
Drill
Mason’s trowel
Stiff-bristle brush
Circular saw with masonry blade
Plugs or seeds for groundcover
Eye and ear protection
Work gloves
3⁄4" plywood
31⁄2" deck screws
Pointing chisel
Pitching chisel
Stone chisel
Hand maul
Dust mask
Chalk or a crayon
Square-nose spade
Crushed stone
Ashlar
Mortar
Capstones

Materials:

Mason’s string
Line level
Rope or hose
Excavation tools
Spud bar
Broom
Stakes
Marking paint
1" (outside diameter) pipe
Coarse sand
Straight 2 x 4
Flagstone
Spray bottle
Stone edging
Sand-based soil or joint sand
Lumber (2 x 2, 2 x 4)
Drill
Mason’s trowel
Stiff-bristle brush
Circular saw with masonry blade
Plugs or seeds for groundcover
Eye and ear protection
Work gloves
3⁄4" plywood
31⁄2" deck screws
Pointing chisel
Pitching chisel
Stone chisel
Hand maul
Dust mask
Chalk or a crayon
Square-nose spade
Crushed stone
Ashlar
Mortar
Capstones

 

Step 1

Construction Details

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.


Step 2

Construction Details

A typical sandset patio has a layer of coarse sand for embedding the flagstones. A subbase 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.


Step 3

Construction Details

Irregular flagstones look natural and are easy to work with in round layouts.


Step 4

Construction Details

Flagstones that are cut into rectangular shapes can be laid in square or rectangular patterns with uniform gaps.


Step 5

How to Build a Sandset Flagstone Patio

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.


Step 6

How to Build a Sandset Flagstone Patio

Set up layout strings to guide the excavation using stakes or batterboards. Excavate the base to a depth of 2" + the stone thickness plus 1⁄2 to 1". Slope the ground away from the house foundation at a rate of 1⁄4" per foot.


Step 7

How to Build a Sandset Flagstone Patio

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 groundcover to grow up to the edges of the stones. If you do plan to use edging, install it now.


Step 8

How to Build a Sandset Flagstone Patio

Fill the site with coarse sand slightly above the screed gauges. With a helper, drag a straight 2 x 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.


Step 9

How to Build a Sandset Flagstone Patio

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.


Step 10

How to Build a Sandset Flagstone Patio

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. 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.


 
 

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