How to Install Stone Steps
Replacing worn-out steps with attractive flagstone steps provides a more inviting entry into any outdoor space.
Pop up the existing stones with hammers and chisels and demolish the concrete with a heavy duty sledgehammer and crowbar. If you want to keep the same approximate dimensions of the old platform, only demolish enough to create a new platform with the same dimensions.
The goal in this project is to create a platform measuring 7 inches high and about 7 inches below the front door’s threshold (the threshold is about 14 inches off the ground and steps should be around 6 or 7 inches high).
The platform will be created from bluestone treads around the edges (measuring 2 inches), cobblestones (measuring 5 inches), and a 1/2" inch mortar joint. If the cobbles are set slightly below grade, this will give the 7-inch height for both the platform and threshold.
The sides (which don’t have the cobblestone risers) and the center (made of 1-inch multiple bluestone) should be demolished to create a surface that, when the material is added, is level. As you demo, check your measurements with a measuring tape.
If the area between your platform and house doesn’t have flashing, install some. Whether it's rubber or tin, flashing will save your house’s foundation by preventing rot.
The design will feature a 7-foot bluestone tread for the front of the platform and two 3-foot pieces on the side. Multiple bluestone pieces will be set in the middle. Find the center of the platform and then play around with ratio and design.
When picking bluestone treads, look for stone that has consistent color and texture. Stay away from treads with bold colors, chips, and divots. Treads generally run $10-12/linear foot.
When selecting multiple bluestone, look for colorful but consistently smooth stones for your project. You should also look for stones as close to the size needed for your project. They’ll probably still require some cutting, so you can cut them yourself with a diamond blade grinder on site or pay the quarry to cut them to size. Multiple bluestone generally runs $4-6/square foot.
The platform front and height will be formed by a row of cobblestones. When choosing cobblestones, you can use new or used cobble. The new cobble (Image 1) is less weathered and has less character than the used cobble (Image 2), but generally costs less.
Before leaving the quarry, also pick up other material needed for their project: Type S cement, mason sand, rebar, and any tools they don’t have. You can have the quarry deliver the material to your site.
Once you’re back at your project site, organize your work area. It will make the setting process easier. With your area organized, mix your mortar.
Don't buy a 'just add water' bag of mortar, cement, and sand. The front steps are an area exposed to the elements and foot traffic, so you should set them with the strongest mortar, which means mixing your own. Mix masonry sand and type S cement (a mixture of mortar and cement) in a 2-to-1 ratio of sand to cement. Mix the material in a wheelbarrow with a mixing hoe. Dry mix the ingredients first and then add water until you reach a consistency close to peanut butter. Depending on the temperature of the day, you should be able to work with the mortar for a few hours.
Mark out the area where you’ll place the row of cobblestones and make sure it’s square from the house. If it’s not, you’ll need to dig a new footing that is square. This new footing should be a little below grade and wide enough to create a base for the cobble. Shovel some of the mortar mixture into the footing, set rebar or stone in the middle of that mortar for strength, and let it set up a bit before setting your cobblestones.
Once the mortar footing has set up, begin the cobble setting process by finding the center point of the cobble row. Find the center of the threshold and at that center point align the square against the house. Align a 6-foot level with the square, and using the level as a guideline, mark the center point in the mortar footing with a trowel.
Start by setting a cobble on each end of the footing and work your way in towards the center. The bluestone treads will overhang the cobble about 1/2 inch on all three sides, with a platform 4 feet off the house the cobblestones should be set at a distance of 3 feet 11-1/2 inches from the house. Secure a piece of rebar on either end of the cobble row and run a level piece of string between the rebar. This will act as a guideline for setting the faces of the cobblestones.
If your cobblestones require cutting to get them to fit, cut one of the center cobbles to hide the cut. Cobblestones can be cut using a chisel, stone hammer, and safety glasses.
As you set the row, secure the cobblestones by building up a berm of mortar and junk stone behind them and tapping them into the mortar footing with a rubber mallet. Once the stones are secured, joint the gaps between the cobblestones using a 1/2-inch jointer. The mortar should be packed tightly to prevent freezing water from getting into gaps and cracking the steps.
Finish by filling the area behind the cobblestones and the new platform base with junk stone and mortar. Let the cobblestones set up overnight.
Begin by setting the treads framing the platform first, starting with the tread running parallel to the door threshold. Prop the treads up on top of two cobbles or bricks; this will make it easier to get your fingers underneath the stone. Mark the center point of the cobblestone row. This should be the same place marked earlier in the mortar. Then, mark the center of the first tread. You will match up these two center points when setting the first tread. Make sure with your measuring tape that the area running from underneath the threshold to the top of the cobbles, when set with treads, will pitch slightly forward.
Trowel 1/2 inch of mortar on top of the cobbles and keep the mortar back about a 1/2 inch from their face. This will keep the mortar from oozing out to stain the face of the stone. Don’t skimp on mortar in the corners. Run your 6-foot level across the mortar before setting the tread to make sure it’s level and smooth.
Set the bluestone tread on top of the mortared cobbles and align the two marked center points. Level the tread front to back and side to side and then make sure that the tread is exactly 4 feet off the house on both ends. Adjustments can be made by with a rubber mallet. Once you have your first tread where you want it, secure the front of the stone with a few shims placed in the mortar underneath. After the stone has set up, the shims will be removed, but in the meantime they’ll ensure that the tread doesn’t move while setting the other stones.
Set the two side tread pieces and make sure that the finished edge is facing out. Repeat the same process for setting the tread: begin with 1/2 inch of mortar, set the stone, check for level, and adjust with a rubber mallet. With the treads set, it's time to set the remainder of the bluestone platform: the multiple bluestone pieces.
The interior part of the platform will be formed by five pieces of multiple bluestone set in a geometric pattern. Check your measurements before you set them. You want your bluestone pieces to fit. Laying the stones out in your yard first and checking those measurements is a good way to test the size. You’re shooting for a 1/2-inch joint around each piece. If cuts are needed you can make them with a diamond blade grinder and water or have the quarries cut them for a fee.
Place enough mortar in the base. It should be about 1/2 inch so the bluestone pieces will be level with the treads. Adjust them with mallets until they’re where you want them. Dry fit the last stone and watch your fingers as you do. The last stone is known as the 'finger pincher' for good reason. Add mortar and set this stone. Adjust all of the stones so that they’re level and at the same height.
Once they've set up for a couple of hours, you can joint the platform. The mortar should easily form a ball when pressed in your palm (Image 1). Use a 1/2-inch jointer and firmly pressed mortar into the joints until they are slightly recessed (Image 2). Follow up the jointing by brushing the joints with a paintbrush, and let them dry for about 12 hours.