Written by Stucco Champions — Southern California’s Authority on Exterior Plastering.

One-Coat Stucco Weep Screed Installation: The 1-3/8" Rule

When installing a "One-Coat" stucco system (which typically involves 1 inch of rigid foam insulation), you cannot use standard hardware. The most common failure we see in these systems is the use of a standard 7/8" weep screed, which is too shallow to accommodate the foam.

To ensure proper drainage and a flush finish, you must use a 1-3/8" Foundation Weep Screed. This specific profile provides the necessary depth for the foam (1 inch) plus the base coat (3/8 inch). This guide breaks down the precision cutting and fastening techniques required to install this critical flashing correctly.

1. The Math: Why 1-3/8 Inch?

Unlike traditional stucco where the wire sits against the wall, a One-Coat system pushes the finish out.
The Equation: 1" EPS Foam Board + 3/8" Fiber-Reinforced Base Coat = 1-3/8" Total Depth.
If you use a smaller screed, the foam will overhang the metal, trapping water and leading to rot. The 1-3/8" screed acts as a track for the foam to rest in.

2. Preparation & Clearance

Before you cut a single piece of metal, establish your grade line. ASTM C1063 and local California codes are strict about ground clearance to prevent moisture wicking.

The "Drop" Rule: The bottom edge of the weep screed should hang approximately 1 inch below the sill plate (where the wood framing meets the concrete foundation). This ensures that if water drains out, it drips onto the concrete foundation wall, not onto the wood framing.

3. Fabrication: Cutting Corners Correctly

You cannot just butt two pieces of metal together at a corner. You must create a lapped joint to prevent leaks.
Tools Needed: Aviation Snips (Green/Red handle) or "M3" straight cutters, Speed Square, Sharpie.

For Outside Corners:

1. Mark the Flange: Measure 1-3/8" back from the end of the screed on the top nailing flange.
2. The 45-Degree Cut: Draw a 45-degree line from that mark toward the nose of the screed. Cut along this line.
3. The Nose Cut: Snip the bottom "nose" (the drip edge) vertically.
4. Result: When you place two pieces together cut in this mirror image, the flanges will overlap flat against the wall, creating a sharp 90-degree corner without a gap.

For Inside Corners:

1. The Measurement: Measure 1-3/8" along the front lip (nose) of the screed.
2. The Reverse Cut: Draw a 45-degree line back toward the flange. Cut this angle.
3. Overlap: When joined with the adjacent piece, the noses should meet perfectly in the corner, while the flanges overlap on the wall.

4. Splicing Joints (Straight Runs)

On long walls, you will need to join two 10-foot sticks of screed. Do not butt them edge-to-edge.
The Lap Method:
1. Cut a small "V" notch in the nose of one piece.
2. Slide the second piece inside the first piece by about 2 inches.
3. This "nesting" creates a continuous channel for the foam and prevents the metal from twisting.

5. Fastening Protocol

Secure the screed to the shear wall or studs.
Fasteners: Use 1-1/4" galvanized roofing nails or wide-crown staples.
Spacing: Place a fastener every 16 inches (hitting studs) along the top flange.
Pro Tip: Do not overdrive the nails. If you warp the flange, the foam board won't sit flat in the track later.

Conclusion: The Track for Your System

In a One-Coat system, the weep screed is more than just a drain; it is the "starter track" for your foam insulation. If this metal is crooked or the wrong size, every sheet of foam you install afterwards will be misaligned. Take the time to level it, lap it, and secure it properly.