Building a Mortared Stone Wall


An old stoneworker's adage describes how you should lay any stone wall: "One stone over two, two stones over one." Let the old saying guide your selection of stones for a mortared wall. And if you're using fieldstone, take another bit of old advice: "Pick stones that nest." That means choosing stones with contours that mate as closely as possible on their meeting faces.

Mortared stone walls need a concrete footing to keep them from cracking due to frost heave. Because a mortared wall is generally heavier than a dry-set wall of the the same size, local building codes often dictate specifications that affect the footings for mortared walls. Many codes require the use of reinforcing rod. Check before you build.

Prestart Checklist

2 to 3 days to lay a 3x10-foot wall

Tape measure, chalk line, level, mason's trowel, mason's line, line level, concave jointer, stakes

Designing layout, excavating, mortaring, lifting and setting stone

Prepare site and order stones

Lumber for stakes, 1-1/2-inch screws, stones, mortar

Step 1

Lay out the site and pour the footing. While the footing cures, divide your stones into size groups. Dry-set the first course, starting with bondstones on the ends and every 4 to 6 feet in between. Choose subsequent stones that fit neatly between them.

Step 2

Take up 3 or 4 feet of the stones and set them to the side in order. Then spread a generous layer of mortar -- at least 1 inch -- on the footing. Set the stones and tap them into place with a rubber mallet.

Step 3

Continue removing stones, spreading mortar on the footing, and resetting the stones in the first course. Fill the gap between the front and rear wythes with smaller stones and mortar. Set a 4-foot level on the stones to make sure they're approximately level. Since the surface of the stones is rough, you won't get a precise reading from the level, just an average indication.

Step 4

As you work, or after you've completed the first course on a short wall, pack mortar into the joints. For any space in the core that's more than 1/2 to 3/4 inch wide, set in a small piece of stone to fill the gap.

Step 5

When you've completed the first course, drive stakes at each end of the wall beyond the footing and tie mason's line tightly between them. Set the line at the height of the next course and use a line level to level it.

Step 6

Selecting stones from the various piles you set out in Step 1, dry-lay the second course of both wythes. Choose stones that will sit approximately 1/2 inch below the staked mason's line. Remove these stones and set them aside in the same order. From this point, you can build your wall with leads -- build up the corners and fill in between them as you would a brick or block wall.

Step 7

Continue setting courses, moving the mason's line to help keep them at the same level. Always choose flat, smooth stones for the visible faces of the wall. Fill in the space between the wythes and mortar the stones. Then dry-fit the next row and reset it, checking the batter as you go. Be sure to lay bondstones every third course, at roughly 4-foot intervals. When the mortar begins to set up, stop laying stone and finish the joints. Cap the wall with a course of flat stones large enough to cover both wythes. When you mortar the capstones, do not finish the joints. Brush them flush with the surface of the capstones to keep water from collecting and freezing there -- it could split the mortar or the stone. If you've mixed your mortar slightly wet to make it more workable, don't set any more than three courses a day -- the weight of the stones will cause the courses to sag before the mortar sets.

Checking the Batter

Slope the sides
Except for those built as retaining walls, mortared stone walls don't have to be battered, but you can taper their sides if you like the appearance of a battered wall. Make a batter gauge and use it to check both wythes.

What If... You're building a mortared fieldstone wall?

Setting uncut fieldstone takes substantially more time than any other stone wall. That's because the stones in the courses must fit together. You'll find yourself engaged in a lot of trial-and-error fitting. Like other mortared walls, a fieldstone wall requires a footing. Check your local codes to make sure your plans meet the requirements.

1. Plan the layout so square stones are set at the corners and flat-faced ones line the edges. Use the largest ones you can find but keep the size relatively consistent. Then remove the stones, mortar the footing, and set the stones in the same order.

2. Fill the core with rubble. Depending on the size of the rubble, fill the core in layers, throwing mortar between layers to bind them together. Smaller rubble is best. Then test-fit the stones for the second course.

3. Cover the core with mortar and pack mortar into the joints of the first course. For the next courses, spread mortar one stone at a time. Use enough mortar to form a bed for each stone.

Finish the Joints: Step 1

Strike joints smooth

When the mortar begins to set up, brush off the excess with a whisk broom or stiff brush.

Finish the Joints: Step 2

If the mortar is firm enough to hold a thumbprint, run a concave jointer over the joints to compact and smooth the mortar. Let the mortar set up a little more and rebrush it if necessary.

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