What Type of Mortar Do I Use for a Stacked Rock Wall?

A stone wall can give your garden timeless appeal. Whether you're looking to build a wall for a raised garden or a small retaining wall, a stacked stone wall can offer elegance without a lot of expense. Stone walls also look better with age. They can be stacked without mortar, but this requires stacking them just so. Adding mortar makes your wall stable and takes the worry away.

Stone Wall with Plants and Flowers
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What Type of Mortar Do I Use for a Stacked Rock Wall?

What to Get

You can buy mortar or make it from one part cement, a small amount of lime and two parts sand. Don't use dehydrated lime because it will cause the stone to lose its color. Mortar is usually one part Portland cement, one quarter to one half part lime and two to three parts sand. Lime helps make the mixture easier to work with. If you choose to make the mortar, mix the cement, lime (not dehydrated lime) and sand completely while dry before adding water.

Mortar Types

There are several varieties of premixed mortar, which is probably the best way to go if you've never worked with mortar before. For a garden wall, mortar mix is a good choice. This is a blend of Type N masonry cement and graded sand. It has good adhesive properties and workability.

If you're building a retaining wall, use a blended mason mix, which includes the heavy-duty mortar type S masonry cement and graded sand. This is high-strength, contractor-grade and pre-blended mortar. This is also ideal for stone columns.

For projects that don't require a lot of mortar, use smaller bags of mortar mix or concrete. These are easier to manage and don't leave you with as much leftover material to store.

There are lots of brands and colors to choose from. Gray is the most popular color and blends in well with stone. White can also work well.

Prepping the Mortar

Use a large bucket to mix the mortar, but make sure you work in small batches so you use all the mortar before it dries. Whether you're making your own mortar or using premixed, make sure the texture of your mortar isn't as thick as peanut butter but thicker than pancake batter. If you add too much water, just add a little more mix.

You should piece together several stones before adding mortar to make sure they fit together. You'll have about an hour to work with the mortar you've made before it dries.

Mortaring the Stones

Apply a base coat of mortar beneath the wall onto a carefully prepared foundation. Let the base coat dry and set for 24 hours and then start laying the stones horizontally. Brush water across each stone before applying the mortar. Mortar adheres better to a clean, wet surface.

Spread mortar across the top of each stone at about 3/8 of an inch thickness, although that will vary considerably if the rocks aren't flat. Just don't go less than 3/8 of an inch. As you pile stones on top of each other, mortar will squeeze out from between the stones. Scrape the excess mortar off the stones with your trowel. Keep a sponge handy to wipe off excess mortar from the face of the stone.

When your wall is finished, let it dry for a couple of days and then enjoy your new stone wall.