Mortared Flagstone Patio
A mortared Flagstone stone patio is a great addition to any backyard. Whether you are covering an old concrete patio or adding a new living space, a natural stone patio will add interest and charm to your backyard.
Download a PDF of our Mortared Flagstone Patio Project Guide
Select a guide section:
- Project Photos
- Required Tools
- Materials Needed
- Coverage Calculations
- Preparation
- Installation
- Project Options
- Maintenance
- The Fine Print
Project Photos
See the photos below for examples of finished projects. Click the thumbnails to view larger images.
Required Tools
- Shovel
- Wheelbarrow
- Trowels (large pointed, small pointed, small margin)
- Levels (torpedo, 2 foot, 4 foot)
- Mason’s Line
- Grade Stakes
- Knee Pads
- Gloves
- Grout Bag
- Wire Brush
- Masonry Sponge
- Rock Hammer or Stone Saw
- Small Sledge Hammer
- Mortar Mixer (optional for large patio)
Materials Needed
- Flagstone 1″ – 2″
- Concrete Mix
- Masonry Sand
- Mortar Type S *
- Portland Cement (optional)
- Fiber Mesh Reinforcement (optional)
* Quikrete Mason’s Mix can be used in place of Type S mortar and Masonry Sand
Coverage Calculations
- Flagstone 1″- 2″ will cover approx. 100 sq ft per ton
- 80 lb. bag of Type S mixed with 160 lbs. of masonry sand will cover 36 sq ft at 1” thick
- 1 bag of Quikrete Mason’s Mix will cover approx. 12 sq ft at 1″ thick
Preparation
- Please remember to call before you dig! Having to repair broken utilities will cost you more time and money then expected. In Georgia, call 1-800-282-7411 or visit www.gaupc.com
- Mark the proposed area to get proper measurements and a visual reference of where your patio will be installed.
- Measure the area. Reminder: When purchasing material account for at least 10% waste due to the shaping and cutting of the stone.
- Keep in mind that patios need to drain rainwater. Slope the patio in one direction at least .25″ for every 1′ of patio. This will keep water away from the house and keep water from pooling on the patio.
Installation
- If you are covering an existing concrete patio, a lot of the work already has been done for you. If you are adding a new patio, you will need to pour a 4″ concrete slab.
- You can use bagged concrete mix for smaller projects or hire a concrete truck for larger ones.
- When pouring a new concrete slab or extending the old one, you will need to excavate the ground 4” for the slab + 1” for the mortar bed + the thickness of the stone to achieve a flush patio surface to the surrounding ground.
- Form the sides of the excavated area with 1”x4” lumber for the straight sides, and for the curved sides you may use masonry siding (Hardie Plank). You will need to rip the siding in half to give you approximately 4” wide bendable form board.
- Make sure your patio forms have proper pitch away from the house.
- Now you’re ready to pour the concrete. Pour the concrete starting at the house and work your way toward the yard. The concrete does not need to be perfectly smooth, just leveled and pitched properly away from the house. A rough finish will help the mortar bed (in the next step) adhere to the concrete slab. Let the concrete dry for at least 24 hours before proceeding.
- Now that the concrete slab is dry, you’re ready to start laying the stone.
- If you are covering an existing slab, use Bonding Adhesive to help the new mortar adhere to the old concrete.
- Lay the stone out around the area, not in it yet. It’s always a good idea to be able to visualize the material you are working with so you can spot that perfect piece.
- Hold onto pieces of stone that have straight edges. You can use them around the straight sides of the patio. This will reduce the number of straight cuts you have to make during the extent of your project.
- When placing the stone, press it firmly into place while wiggling it side to side and slightly rotating it. Air pockets under the stone are your enemy in this case. Air pockets and voids mean there is no support under the stone leading to cracked stones in the future.
- Place a shovel full of the mortar mix on the patio at the highest point and place a stone down on the mortar bed. Push and slightly twist back and forth until you have approx. 1” of mortar underneath and the stone is at the correct elevation. Repeat the same process at the lowest end of the patio. You now can place the Mason’s Line across the stones from the highest end to the lowest end of the patio. This line will act as a guide for you to place stones in between keeping proper pitch.
- Constantly check the level of your stones with the torpedo level, and check how level they are to each other with the 2′ or 4′ level. If a stone is out of level you can always add or remove mortar from underneath it. A rubber or rawhide mallet will help you tap it into alignment. Rawhide is great because it does not leave marks on the stone, while some rubber ones will.
- When laying the stone start near the house and work your way toward the yard.
- Try to keep the joints consistently around 1″.
- Test fit each piece before placing mortar under it. Don’t spend too much time on one piece. The rule of thumb is: “If you have to turn or flip the stone more than 3-4 times and it still does not fit, toss it to the side and try another.” It will fit somewhere else.
- Reshaping some pieces of stone will be required. Use the rock hammer or stone saw to shape them to the desired contour.
- Once all the stones are set in place and the mortar is dry then you will be ready to grout the joints.
- You can use the same mortar used to set the flagstone or try a different color to match your stone.
- Use a grout bag to place mortar into the joints. You will fill the grout bag with mortar and squeeze down into the joints slightly overfilling them. It’s just like a cake icing bag but bigger, and doesn’t taste as good either.
- Once the grout has dried to the point that it is firm to the touch but not completely dry, you can scrape the excess off with the side of your trowel. You may need to use a wire brush to do a detailed cleaning of the grout. After the mortar has been cleaned you will need to wash it with a masonry sponge to clean the mortar haze from the stone.
- When finished cleaning you may want to lightly mist the patio every so often to allow the grout to dry slowly if it is in direct sun or very hot when installing.
Project Options
- You can add Portland Cement to the mortar mix to add strength to your patio. Use one bag of Type S mortar to half a bag of Portland Cement and 160 lbs. of masonry sand.
- Add Fiber Mesh Reinforcement to the concrete mix to give more strength to the concrete slab.
- Consider using a sealer designed for stone and concrete. This will keep the stone from getting stained and in some cases will enhance the stone’s natural color. During freezing temperatures, sealing prevents water from entering cracks in the stone, limiting further cracking and splitting due to expansion when water freezes.
Maintenance
- Regular maintenance will include sweeping or blowing debris with a leaf blower from the patio weekly and more often in the fall of the year.
- If your new patio gets soiled you can wash it with a sharp stream of water from your hose.
- You may want to use a mildew remover designed for concrete once a year to keep your patio looking new or you can let it weather and look as if it’s always been there.
- We recommend that you clean the patio every few months if it is located in deep shade. The shade will not allow the stone to dry completely, becoming slippery when wet from algae and mildew growth.
The Fine Print
Please be aware that each project is unique and may pose different obstacles and circumstances that this guide cannot foresee. It is intended as a reference only. Most of these installation techniques are great for our geographic location here in Atlanta, GA. Soil conditions and climate play a large role in how each project is constructed. For example, if you live in the Northeast you will have to use a deeper base material to account for the freeze/thaw cycle that is notorious for upheaving patios. Stone Forest cannot be held liable for any damages incurred by the use of this guide.
Please seek a professional contractor’s advice if you are uncomfortable with undertaking a project you have not completed before.