Flagstone is a popular material for patios, pathways, and other hardscaping projects. Composed of quarried stone slabs, flagstone has an organic, natural aesthetic that can complement gardens, yards, and rustic architecture. Installing a flagstone patio or walkway requires some planning and preparation, but can be a relatively easy DIY project if you have the right materials and tools. Here’s what you need to know about working with flagstone for your outdoor living space.
Choosing Flagstone
Flagstone comes in a variety of natural stone types depending on the quarry. Common types of flagstone include:
- Sandstone – Rustic brown, red, grey, and buff colors. Softer and easier to cut than other flagstones. Prone to flaking over time.
- Slate – Dark grey to black color. Very durable with a smooth surface. Can be slippery when wet.
- Bluestone – Blue-grey color. Resistant to weathering and provides good traction.
- Limestone – Tan or grey color. Comparatively soft but weather resistant.
- Quartzite – Variegated colors including reds, browns, tans, and grays. Very hard and dense. Withstands weathering.
The type of flagstone you choose will depend on the look you want as well as your budget. Softer sandstones tend to be less expensive than harder slates and quartzites. Determine how much foot traffic the area will need to withstand, as harder stones will be more durable.
Purchase flagstone from a trusted quarrier or stone supplier to ensure it is of consistent quality and appearance. Examine the stone slabs carefully to make sure they are even in thickness, with clean edges and no major cracks or flaws. Flagstone is sold by the square foot or ton. Order 10-15% extra to allow for unusable pieces and mistakes.
Preparing the Base
Proper base preparation is key for a long-lasting flagstone installation. The base supports the weight of the stone and prevents shifting and settling over time.
For patios and walkways, dig out the top 6-12 inches of soil and fill with compacted gravel, decomposed granite, or crushed stone. Compact the base in 4 inch layers using a hand tamper or plate compactor. The finished base should be 4-6 inches deep.
Incorporate a layer of coarse sand or stone dust 1-2 inches deep on top of the compacted base. This helps level and fill gaps between flagstone pieces during installation.
Make sure the base extends beyond the planned flagstone area by 6-12 inches to keep the edges stable. Use landscape edging to contain the base if needed.
Sloping the base slightly for drainage and using a porous fill material like gravel can help prevent water pooling under flagstone.
Cutting Flagstone
Most flagstone projects will require some minor cutting and shaping of pieces to fit. With the proper tools, cutting flagstone is straightforward.
For irregular shaped stones, use a stone chisel and mallet to chip small pieces off the edges. Tap lightly and take your time. Rougher edges can match the natural look of flagstone.
For straight cuts, rent a electric wet saw with a diamond blade. Mark cuts carefully and saw slowly to avoid cracking the stone. Wear safety goggles and a mask when cutting.
Use a circular saw with a masonry blade to cut notches or curves for a custom fit. Cut off a small amount at a time to maintain control.
For sandstone and limestone, a simple hammer and stone chisel can make most cuts by patient chipping. Quartzite and slate will likely require power tools.
Always cut flagstones outside or in a well-ventilated area to avoid breathing stone dust. Have a spray bottle on hand to keep stones damp while cutting to minimize dust.
Installing the Flagstone
Once your base is prepped, you’re ready to start setting the flagstones. Plan out the layout and play with different patterns and orientations before permanently placing stones.
Work outward from one corner or a straight edge border. Set larger squared pieces first along the edges, then fill in the middle with irregular shapes.
Place stones close together, maintaining 1⁄8-1⁄4 inch gaps for drainage and sand/dust fill. Use stone chisels and rubber mallets to adjust and level pieces. The tops of stones should be roughly even when complete.
Sweep sand or stone dust over the surface to fill joints after setting several stones. Tamp down with a rubber mallet. Add more fill as needed until joints are filled flush.
Use thin stone shards and pieces to fill small gaps, completing your installation. Avoid using concrete or mortar, which prevents natural shifting and can crack flagstone.
Seal patio and walkway joints with polymeric sand every 1-2 years. This prevents weeds and stabilizes joints long-term. Sweep lightly before reapplying.
Pro Tip: Stack alternating rows of rectangular and irregular flagstones in a running bond pattern for a classic patio look.
Caring for Flagstone
Flagstone’s natural beauty develops character over time through weathering. But proper care keeps it looking great and prevents major damage or deterioration.
- Sweep occasionally with a stiff broom to remove dirt and debris from the surface and joints. This prevents buildup that can stain stone.
- Pressure wash cautiously every few years if needed. Avoid high pressure levels that can dislodge fill material from joints.
- Reapply polymeric joint sand after cleaning to refresh stabilization. Fills cracks and gaps that may form over time.
- Watch for burrowing insects, weeds, or evidence of shifting or settling. Fill joints and reset stones as needed to prevent long term issues.
- Reseal flagstone every 3-5 years with a stone sealer. Enhances color and provides protection from the elements and staining.
Avoid using salt for de-icing flagstone walkways in winter. Salt can deteriorate and effloresce many types of flagstone. Use sand or clay-based products instead.
Design Ideas
Beyond basic patios and pathways, flagstone lends itself to all kinds of creative hardscape projects:
Steps – Line flagstone steps with a roughhewn look. Use irregular sizes and shapes for a natural feel.
Borders – Accent gardens and beds with a flagstone border. Combine with brick or pavers for contrast.
Landings – Extend a flagstone path to a landing at the foot of a door or gate. Carry the design to a porch or patio.
Fire Pits – Circle an outdoor fire pit or cooking area with rustic flagstones. Great for cozy gatherings.
Retaining Walls – Use stacked flagstone as a short garden retaining wall. Allow drainage through the stones.
Edging – Edge planting beds or tree rings with a single line of flagstones laid vertically. Quick and stylish.
Planters – Construct unique planter boxes from flagstone slabs and boulders. Allow greenery to soften the stone look.
Mixing flagstone sizes, colors and textures creates visual interest. Leave gaps for planting pockets and fill with gravel or decorative stone for a garden path look. The organic nature of flagstone pairs well with the natural world.
Pros and Cons of Flagstone
Flagstone has characteristics that make it a good choice in many circumstances. Consider the advantages and disadvantages when planning your project:
Pros
- Natural, irregular beauty that replicates stepping stones. Unique and rustic.
- Variety of stone types to fit needs for appearance, durability, and cost.
- Can be installed by DIYers with proper base prep and basic tools. Relatively easy for small projects.
- Structurally sound and will not crack or warp like other materials. Long lasting when properly maintained.
- Provides good traction from stone’s coarse texture. Does not get as slippery as tile or poured concrete when wet.
Cons
- Flagstone won’t have consistent shape or color like pavers or concrete. Requires embracing an organic look.
- Durability and performance varies by stone type. Softer sandstone relatively high maintenance compared to hard slates.
- Requires cutting and fitting of stones during installation. More labor intensive than laying brick or pouring concrete.
- Potential for weed growth and settling issues if base not adequately prepped and joints not properly filled.
- Sealing required periodically to protect against weathering stains. Reapplication of joint material needed over time.
- Can crack and deteriorate faster in colder climates with freeze-thaw cycles if not installed below the frost line.
Overall, flagstone offers timeless elegance for patios, walkways, and landscape features in climates not prone to extreme winter freezes. Proper selection, preparation, and maintenance will lead to lasting enjoyment of its natural style.
Frequently Asked Questions
Here are answers to some common questions about flagstone patios and walkways:
What size flagstone should I use?
Flagstone range from thin 1-2 inch pieces to 4-6 inch thick slabs. 2-3 inches provides good durability and easier handling. Mix in different sizes for visual interest.
How much does a flagstone patio cost?
Flagstone installed is roughly $10-20 per square foot depending on materials and labor. DIY costs can be $3-8 per square foot. Variable costs include delivery, base materials, and stone type.
Can I install flagstone over existing concrete or pavers?
Yes, but at least 2 inches of crushed gravel base should still be laid over the surface for proper support and drainage. The old surface must be in good structural condition.
What tools do I need to install a flagstone walkway?
Shovels, wheelbarrows, 4 foot level, tape measure, rubber mallet, chisels, broom, tamper, plate compactor, and potentially a wet saw. A few specialty tools make the job much easier.
How thick should the gravel base be under flagstone?
4-6 inches of compacted gravel or crushed stone is ideal. 3 inches may suffice for light foot traffic areas. At least 6 inches for driveways or heavily used surfaces.
What is the best way to cut flagstone?
For detailed cuts and straight edges, use an electric wet saw with a diamond blade. For quick shaping and smaller cuts, use a hammer and stone chisels of various shapes and sizes.
How do I keep weeds from growing in flagstone joints?
Promptly filling gaps with sand or stone dust inhibits weed seeds. For prevention apply polymeric joint sand sealers which block growth when cured. Pull existing weeds by hand or spot treat with vinegar or soap.
Can flagstone crack from freezing temperatures?
Yes, flagstone is susceptible to freeze-thaw damage, especially softer, porous stones. Install below the frost line and allow proper drainage underneath to reduce risk of cracks from shifting and ice expansion.
How often should flagstone be sealed?
Sealing is recommended every 1-3 years for optimal protection. Harder stones like slate and quartzite may only need sealing every 3-5 years. Softer sandstone should be sealed more frequently, every 1-2 years.
Conclusion
The natural charm and durability of flagstone makes it a go-to material for patios, pathways, steps, and landscape features. With careful planning, proper base installation, and routine sealing and maintenance, flagstone can remain beautiful for decades. Pay attention to selecting the right stone, allowing for drainage, and completely filling all joints during the initial project. Flagstone’s high-end look can increase property value for a relatively low investment. With a little time and effort, you can enjoy a lovely flagstone oasis right in your own backyard.