How to Mortar Flagstone

Lay the flagstone out onto the surface to be laid with flagstone. Experiment with the layout until you are satisfied with the overall appearance. Remove the flagstones one at a time and place them aside in the same configuration as the layout on the surface.

Add 1 part cement to 4 parts sand into a cement mixer and mix with enough water to make a stiff mortar mix. Add the water slowly until you achieve the correct consistency.

Pour the cement at one side of the surface to be laid with flagstone. Drag a board across the surface to distribute an even layer of cement onto the surface. If you are laying a wide surface such as a patio, ask someone to help you drag the board across the surface. The cement layer should be approximately 2 inches thick.

Place the flagstone into the cement layer so that approximately half of the thickness of the flagstone is in the cement. Turn the flagstone slightly as you press it into place to remove any air pockets from underneath the stone. Continue in this manner until you have covered the surface. Allow the mortar to dry for 24 hours.

Place 1 part cement and 1 part sand into the cement mixer. Add enough water to create a stiff mortar mix.

Use a trowel to fill a grout bag with the mortar from step 5. Grout the joints of the flagstone with the grout bag.

Mist the surface with a garden hose. Allow the surface to dry five to seven days before using it.