How do I install cultured stone on an exterior wall?
Exterior cultured stone install is a 3–5 day project for a typical wall section. The bi...#
Exterior cultured stone install is a 3–5 day project for a typical wall section. The big difference from interior: you need a weather-resistant barrier (Tyvek or equivalent) plus metal lath nailed every 6" before you can apply mortar. Once the prep is done, the stone-setting itself is identical to interior work.
The order of layers on a residential exterior wall, from inside out:
1. Sheathing (existing — typically 7/16" OSB or plywood)
2. Weather-resistant barrier (Tyvek, Typar, or 30# felt — overlapped 6" at seams)
3. Metal lath (galvanized, nailed every 6" through to studs with galvanized roofing nails)
4. Scratch coat (1/2" Type-S mortar, scored horizontally)
5. Stone (corners first, then flats)
6. Optional grout + sealer
The WRB and metal lath are non-negotiable. They're what keeps water away from your sheathing and what gives the mortar something to grip. Skipping these will cause the stone to fall off in 5–10 years and rot the wall behind it.
Critical detail at openings: install metal flashing above all windows, doors, and any horizontal surface where water could collect behind the stone. Also leave a 2" gap at the bottom of the wall to allow weep water to escape. This is called a 'weep screed' and is required by most building codes.
The walkthrough.#
Most US building codes require a 2" gap at the bottom of exterior masonry to let weep water escape. Skipping this is a common DIY mistake that fails inspection and traps moisture.
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