How to Repair Sandstone Steps

Mason Mark McCullough takes us on a house call to Dallas, Texas, where a homeowner’s sandstone steps are starting to cause issues. After noticing that the bond between the pre-existing concrete steps and new sandstone veneer is failing, Mark and the homeowner get to work.

What is Sandstone?

Sandstone is known for its rustic look and earthy color palette. It can be used for walls, fireplaces, and flooring and is used in indoor and outdoor spaces. Sandstone is not only affordable, but it is also very durable.

How To Repair Sandstone Steps

1. Check each of the existing stones to assess whether they are securely embedded. Stones that wiggle (particularly those at the edge of the step) will need to be removed during the repair. Stones that are securely embedded can remain in place.
2. Carefully chip away at the mortar joints around the stones that need to be removed. Attempt to strike the mortar joint with the chisel and hammer, not the edges of the stones themselves. Start with the joints around the stones and then chip away at the joint underneath the stone until it’s loose enough to remove. Note: Do not pry up or the stone will likely break.
3. Continue to remove the mortar that adhered the stone to the concrete underneath. Steps are required to be of a uniform height, and removing this mortar allows for a new bed of mortar to be applied without lifting the stone above the others. Once the mortar is removed, brush the entire area with the masonry brush to remove the dust and aggregate, and pour water over the stone to prevent it from sucking the moisture out of the new mortar.
4. Apply concrete additive to the area and spread it over the concrete, stones, and abutting mortar joints. This will allow the new mortar to bond better with the existing masonry surfaces, ensuring the stones don’t come loose in the future.
5. Mix water and mortar mix in a bucket until it reaches the consistency of oatmeal. Pack the mortar joints around the repair area with mortar, using the margin trowel to press it into the nooks and crannies. Once packed, use a trowel to lay a bed of mortar into the repair area. Create furrows by lightly pressing down on the mortar mix at a slight angle every half-inch or so. Note: Don’t apply too much mortar mix to any steps, or it may not be possible to press the stone down to the required height.
6. Use the trowel to back-butter the sandstone with mortar mix. Place the stone into the repair area and press down into the bed of mortar, wiggling it back and forth slightly to push out air bubbles and excess mortar. Use the handle of the trowel to tap it down to the height of the other stones.
7. Use a trowel to apply mortar mix to the joints around the stone, packing it into the nooks and crannies. Once sufficiently packed, use the paintbrush to drag the joints lighty, bringing the aggregate to the surface to recreate the rustic look.
8. Use the sponge and water to smooth the edges of the mortar joints and remove mortar from the stone’s face. Allow the area to dry for a few minutes before sponging the joints again. Allow the mortar to set before using the steps.

Resources

To repair the stone steps Mark removes old mortar and loose stones, using a hammer and chisel. To apply mortar to smaller areas between stones, Mark uses a 5×2 margin trowel. To spread mortar over stones and larger areas, Mark uses a brick trowel. To finish the mortar joints, Mark uses a concave jointer. He then textures the mortar joints with a soft bristle brush.

Expert assistance by Metro Brick Repair. Materials supplied by The Mountain Stone Supply.

Materials

• Concrete additive
• Mortar mix
• Sandstone veneer (if existing veneer breaks)

Tools