Building a flagstone patio is a satisfying weekend project that gives you a natural stone surface for a fraction of a contractor's price. The short answer: excavate, compact a gravel base, add a bedding layer of sand or decomposed granite, set the flagstones with even joints, level each one, then fill the joints with sand, DG, or polymeric sand. The dry-laid method below is the most DIY-friendly. Here is how to do it.
What you need
- Flagstone sized for your patio, ideally a similar thickness for easier leveling.
- Crushed aggregate base for the structural layer.
- Bedding sand or decomposed granite to set the stones in.
- Joint fill: sand, decomposed granite, or polymeric sand.
- A plate compactor, a level, a rubber mallet, a shovel, and a broom.
Step 1: Excavate
Mark your patio shape and dig down enough for your base plus bedding plus the stone thickness, so the finished surface sits flush with the surrounding grade. Slope the excavation away from any structure by about a quarter inch per foot so water drains off the patio.
Step 2: Build and compact the base
Add crushed aggregate base in lifts, raking each level and compacting with the plate compactor before adding the next. A solid, compacted base is what keeps the patio from settling and rocking, so build it up to within a couple of inches of finished height and compact it firm.
Step 3: Add the bedding layer
Spread a bedding layer of sand or decomposed granite over the compacted base and screed it level. This is the layer you set the stones into and adjust for the slight thickness differences between flagstones.
Step 4: Set the flagstones
Lay the stones like a puzzle, fitting their natural edges together with consistent joint gaps. Set each piece into the bedding, tap it down with a rubber mallet, and check it with a level. Add or remove bedding under a stone to bring it flush with its neighbors. Work in from one edge so you can kneel on set stone as you go.
Step 5: Fill the joints
Once all the stones are set, sweep your joint fill into the gaps. You have three common choices:
- Sand or decomposed granite: a soft, natural look that is easy to refill over time.
- Polymeric sand: hardens when wetted, resists weeds and washout, and locks stones together.
- Planting: low ground cover in the joints for a green, garden look.
Sweep off the excess, settle the fill with a light misting, and top off any low joints.
Frequently asked questions
What do you put under flagstone for a patio?
A compacted crushed-gravel base topped with a bedding layer of sand or decomposed granite. The base provides structure, and the bedding lets you level each stone despite slight thickness differences.
What do you fill flagstone joints with?
Sand, decomposed granite, or polymeric sand. Sand and DG give a soft, natural look that is easy to refill. Polymeric sand hardens to resist weeds and washout. Some people plant ground cover in the joints instead.
Can you lay flagstone without concrete?
Yes. The dry-laid method sets flagstone on a compacted gravel base and bedding layer, with no concrete. It is the most DIY-friendly approach and lets water drain through the joints.
How thick should flagstone be for a patio?
Patio flagstone is commonly an inch or more thick for durability underfoot. Choosing stones of similar thickness makes leveling much easier during install.
Get your flagstone
Browse our flagstone and pick up decomposed granite for bedding and joints. Not sure flagstone is the right call? Compare it to pavers in our flagstone vs. pavers guide. We deliver nationwide from our California yards.