Ask the Builder: Installing mortarless stone veneers

Do you follow trends in design, building, clothes and so forth? You probably realize that the motive force behind these changing trends is to pry hard-earned money from your wallet or savings account.

Are you old enough to remember when pink and gray ceramic tile was the rage? How about polka-dot patterned shirts with wide collars and bell-bottom jeans? I know, I’m dating myself!

But what about a trend that started out in the past decade and appears to still be gaining in popularity? I’m talking about mortarless stone veneer. You may think this is a new technology, but it’s not. Not by a long shot.

The Egyptians used mortarless masonry on a huge scale in Giza, home of the great pyramids and bedsheets. The giant pyramids had a smooth veneer of giant slabs of stone fitted with absolutely no mortar.

The Peruvian Indians did the same thing thousands of years ago at Machu Picchu high up in the Andes Mountains. Moreover, they did this with no power tools, diamond wet saws or dry-cut abrasive blades attached to a handheld saw.

These two civilizations weren’t alone. There are many examples of stone walls, buildings and arches built without mortar. Instead, master stonemasons took the time to fit the stones together much like pieces of a high-quality jigsaw puzzle. The good news is you can purchase stone veneer for your home and follow in the footsteps of the master builders of old.

Recently, a woman who tunes in to my video livestream on my Ask the Builder YouTube channel each weekday shared how she’s using thin pieces of interlocking natural stone as a surround for her new fireplace. The old fireplace developed a crack in the firebox and had to be replaced.

What’s interesting is the hearth and the wall above the fireplace were covered with large pieces of multicolored slate that is not being replaced. The new stone veneer around the fireplace blends really well with the existing slate. Don’t be afraid to mix different stones, textures and sizes.

Months ago, a close friend of mine inherited an ocean-front condominium in Southern California built more than 40 years ago. The interior fireplace had a dated tile surround, and it was time to replace the tired tile. He and his wife chose to use thin mortarless stone veneer that she installed.

The color was fabulous, and the 1½-inch high pieces of stone were the perfect scale to match both the room and the fireplace. She told me after the job was finished how easy it was to work with the stone.

Keep in mind this amazing building material can be used outdoors with great success so long as you install it correctly. Just a few miles from my home, a new building sports a mortarless stone veneer that’s about 1½ inches thick. The pieces of natural granite have a random texture that’s exposed to the weather.

While it looks like the stone pieces are random in size, they’re not. The different sizes have been saw cut at a factory to precise dimensions so you can stack the stones randomly and never worry about a pesky gap. It’s very similar to an Ashlar pattern in slate flooring.

There are different ways to install these magic stone veneers. Some come as panels that you screw to the wall. Others are individual pieces of stone you adhere to an interior or exterior wall with Portland-cement-based thinset or traditional brick mortar applied to the back of each piece of stone.

If you use traditional mortar, be sure to add some hydrated lime. I have a formula for this at askthebuilder.com. Keep in mind the cumulative weight of the stone veneer is considerable. Most natural stone weighs in at about 150 pounds per cubic foot.

The stone that surrounds the two fireplaces I previously discussed could easily weigh about 600 pounds. This means that, as you install the stone, the first course needs to be solid and able to support the weight of the stones as you stack them.

When using mortarless stone veneer outside on your home to hide a bland concrete foundation wall, it really pays to have a small shelf or ledge cast into the concrete.

The craftsmen who build cast, or poured, concrete walls can do this with minimal effort. All the weight of the stone is then transferred to the footing, and there’s little danger of the veneer failing in the future.

Be sure your architect allows the face of your exterior frame walls covered with sheathing to be flush with the overall face of the stone veneer. This is easy to achieve using a wider bottom plate.

If your exterior siding is wood, vinyl, fiber cement or another similar product, it will be able to overlap the stone veneer just like roof shingles overlap the row below. This is vital to ensure that no water ever gets to the wood framing that may make up your exterior walls.

As with every product, be sure you read the installation instructions. Don’t hope the job is going to be done right. The instructions are very easy to understand.

Have a meeting with the contractor or stonemason before they start on this phase of work and review the instructions. You should only hope for things that you can’t control, like the weather. You can control how all the work is done on your home.

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