Stone Wall Calculator

Dry Stack vs. Mortared Stone Walls

Dry stack stone walls are built without mortar, relying entirely on the weight and friction of carefully fitted stones. They've been used for thousands of years and, when built correctly, last for centuries. The key is selecting stones with flat faces and fitting them tightly so they interlock. Dry stack walls are flexible and shift with frost heave and ground movement without cracking, making them ideal for agricultural boundaries and garden walls.

Mortared stone walls use mortar to bond stones together, creating a more rigid, permanent structure. Mortared walls can be thinner than dry stack walls of the same height and are better for high-traffic areas or walls that need a clean, finished appearance. The downside is that mortar cracks under movement, so you need a proper footing and well-drained backfill to prevent settling and frost damage.

For retaining walls, mortared construction is stronger and allows for thinner walls, but requires weep holes or drainage pipes to prevent hydrostatic pressure buildup. Dry stack retaining walls drain naturally through the joints, so they're less prone to water-related failure. However, they must be thicker and battered (angled back) more aggressively to resist soil pressure.

Stone Selection and Sourcing

Fieldstone is the classic choice for dry stack walls. It's rounded by glacial action and found in fields, forests, and riverbeds. Fieldstone is typically free for the taking on rural properties or sold by the ton at quarries and landscape suppliers. The irregular shapes require skill to fit, but the result is a natural, rustic look that blends into the landscape.

Flagstone is flat, stratified sedimentary rock that splits into slabs. It's ideal for stacked stone walls and veneers because the flat faces require minimal fitting. Flagstone is more expensive than fieldstone but faster to work with and yields a more uniform appearance. Common types include bluestone, limestone, and sandstone, each with distinct color and texture.

Quarried wall stone is cut into roughly rectangular blocks, resembling oversized bricks. It's the easiest to stack and build with, making it a good choice for beginners or large projects where speed matters. Quarried stone costs more than fieldstone but less than flagstone, and it installs quickly with less waste. It's available in granite, limestone, sandstone, and basalt, offering a wide color palette.

Building a Dry Stack Stone Wall

Start with a solid base. Excavate to firm soil or below frost depth, then lay a foundation course of the largest, flattest stones. This course should be slightly below grade and perfectly level across its length. The foundation stones bear the entire weight of the wall, so choose wisely and fit them carefully.

Build up in courses, alternating joint lines like brickwork. Never stack joints vertically—it creates a weak plane where the wall can split. Fit each stone so it contacts the stones around it on at least three sides, with no rocking or gaps. Lay stones flat, not on edge, and orient the longest dimension into the wall to tie the inner and outer faces together.

Batter the wall by setting each course back slightly from the one below. A 1-inch setback per vertical foot creates a stable, self-bracing structure. Use tie stones (long stones that span the full thickness) every few feet horizontally and vertically to lock the two faces together. Fill the center with smaller stones and rubble, compacting as you go to prevent voids. Cap the wall with large, flat stones laid across the full width, creating a finished top and locking the structure together.