Written by Stucco Champions — Southern California’s Authority on Exterior Plastering.
The Skeleton of Stucco: How to Install Wire for a One-Coat System
In the world of stucco, the "One-Coat System" is a bit of a misnomer. It is actually a high-performance assembly involving rigid foam insulation, a fiber-reinforced base coat, and a finish texture. But the system is only as strong as its skeleton: the Lathing Wire.
Unlike traditional 3-coat stucco that uses expanded metal diamond mesh, One-Coat systems typically utilize a specific 20-Gauge Woven Wire (often called "chicken wire" or "stucco netting"). Installing this correctly is the difference between a wall that lasts 30 years and one that cracks in 30 days. This guide walks you through the professional lathing protocol.
1. The Anatomy of One-Coat Lath
Before you start stapling, you must have the right material. Do not use heavy diamond mesh for a One-Coat system over foam; it is too rigid and difficult to embed.
- The Wire: 20-Gauge Galvanized Woven Wire (1-inch hex pattern).
- The Fasteners: You need a pneumatic staple gun capable of shooting heavy-duty lath staples.
- The Safety Gear: Metal snips are sharp. Wear heavy leather gloves and ANSI-rated eye protection.
2. Step 1: The Weep Screed Foundation
You cannot hang wire until your bottom termination is set. Ensure your Weep Screed is installed level at the foundation line. The wire will eventually lap over the solid flange of this screed, but never block the weep holes.
3. Step 2: Hanging the Wire (The Horizontal Run)
Wire comes in rolls. We install it horizontally, working from the bottom up.
- First Course: Align the bottom edge of the wire with the bottom edge of the weep screed flange.
- Temporary Tack: Use a roofing nail or two at the top corners to hold the wire in place while you position it.
- Pull it Tight: Loose wire causes wavy walls. You must pull the wire taut against the foam insulation before stapling. It should sit flat, with no "bellies" or loose pockets.
4. Step 3: The Fastening Schedule (ASTM C1063)
This is where DIY projects fail. You cannot just staple randomly into the foam. Staples must hit the wood studs.
You must place a staple every 6 inches vertically along every stud.
Staple Depth: If you are going through 1-inch foam, you need a staple long enough to penetrate the wood stud by at least 3/4 inch. Typically, this means a 2-1/2" leg staple.
5. Step 4: Overlaps and Seams
Where one piece of wire meets another, you must create a structural bond.
- Horizontal Laps: The top sheet must overlap the bottom sheet by at least 2 inches. This "shingle lap" ensures water runs down, not behind.
- Vertical Laps: Where rolls end, overlap the vertical seams by at least 6 inches and ensure the seam falls on a stud for secure fastening.
6. Step 5: Corner Management
Corners are the highest stress points in a stucco home. Never end a sheet of wire at a corner.
You must wrap the wire around the corner (inside or outside) by at least 12 inches. This creates a continuous metal reinforcement that prevents the corner from cracking open during thermal expansion or seismic activity.
Conclusion: Tight and Right
A properly lathed wall should look neat, tight, and uniform. If the wire is baggy, the stucco will be uneven. If the staples miss the studs ("shiners"), the wall will have no structural support. Take your time—the lath is the only thing holding the cement to your house.
Last week, we shared Fog Coating vs. Painting Stucco: A Comprehensive Guide. Once your system is installed, know how to finish it correctly.