Written by Stucco Champions — Southern California’s Authority on Exterior Plastering.
The Comprehensive Guide to Stucco Lathing Wire Types
Stucco lathing is the hidden backbone of your home’s exterior. While the finish coat gets all the aesthetic glory, the wire lath underneath is doing the heavy lifting—literally holding thousands of pounds of cement to the wall. Choosing the wrong gauge or profile can lead to sagging, cracking, and catastrophic delamination.
In Southern California, we primarily deal with two systems: Three-Coat and One-Coat. Each requires a specific type of wire to meet code. This guide breaks down the metal mesh options available and when to use them.
1. The Heavyweight: 17-Gauge Woven Wire
This is the industry standard for Traditional Three-Coat Stucco. It looks like heavy-duty chicken wire.
- Strength: 17-gauge steel is thick enough to support the full weight of a 7/8" cement wall (approx 10-12 lbs/sq ft).
- Self-Furring: It is "crimped" (bent) during manufacturing to hold the wire 1/4 inch away from the wall. This allows the scratch coat to flow behind the wire, fully embedding it in cement. If you use flat wire, the cement won't key in, and the wall will fail.
- Application: Residential exterior walls over plywood sheathing.
2. The Lightweight: 20-Gauge Woven Wire
This is a thinner, more flexible version of the 17-gauge wire.
- Use Case: Specifically designed for One-Coat Stucco Systems over foam. Because one-coat stucco is lighter (fiber-reinforced) and thinner (3/8"), it doesn't require the heavy steel support of the 17-gauge.
- Cost: slightly cheaper and easier to cut, but do not use this for a heavy three-coat system; it will sag.
3. Expanded Metal Lath (The Diamond Mesh)
This looks like a steel sheet with diamond-shaped holes punched into it. It is rigid and sharp.
- Stone Veneer: It provides a stronger grip for heavy stone.
- Transitions: We use strips of this to reinforce corners or connect different materials (e.g., wood to stucco).
- Soffits/Ceilings: Because it is rigid, it doesn't sag when applying stucco overhead.
4. High-Rib Lath: The Ceiling Specialist
This is expanded metal lath with deep V-grooves (ribs) running through it for extra stiffness.
- Application: Exclusively for Ceilings and Soffits. The ribs prevent the wet cement from bowing the lath downward while it cures. It spans joists without sagging.
- Warning: It is extremely hard to cut. You need a grinder or heavy-duty snips.
5. Paper-Backed Wire (K-Lath)
This is wire mesh with the building paper already attached to the back.
Pros: Faster installation (one step).
Cons: Harder to ensure a proper "shingle lap" at the seams. We generally prefer installing paper and wire separately to guarantee the waterproofing layer is perfect, but K-Lath is common in tract home construction.
Regardless of the wire type, the laps are critical.
Horizontal Laps: Minimum 1 inch.
Vertical Laps: Minimum 2 inches.
Wire-tie the laps together between studs. If the wire isn't continuous, the stucco will crack in a straight line right at the seam.
Conclusion: Match the Wire to the System
Don't mix and match. If you are doing a heavy custom home finish, use 17-gauge. If you are doing a lightweight retrofit, use 20-gauge. And if you are hanging stone or stuccoing a ceiling, switch to expanded metal. The wire is the skeleton; make sure it's strong enough to hold the skin.
Last week, we shared Stucco Scratch Coat vs. Brown Coat. Once the wire is up, learn how to apply the base coats.