Written by Stucco Champions — Southern California’s Authority on Exterior Plastering.
Navigating Vertical Weep Screed Installations: Best Practices and Considerations
In a perfect world, foundations are flat, and weep screed runs in a straight, uninterrupted horizontal line. In Southern California, however, we build on hills. From Laguna Beach to the Hollywood Hills, "Stepped Foundations" are the norm.
When the foundation steps down, the weep screed must follow. This creates a complex waterproofing challenge: running a drainage component vertically. This guide explains the correct geometry for stepping weep screed down a slope without violating building codes.
1. The Geometry of the "Step-Down"
Code (CRC/IBC) requires the weep screed to be placed at the foundation plate line (where the wood meets the concrete). When the concrete foundation steps down the hill, the weep screed must create a "Z" pattern or a "Waterfall" effect.
- Horizontal Run: Drains water out.
- Vertical Drop: Transitions the screed to the lower level.
- Lower Horizontal Run: Continues the drainage plane.
2. Vertical Weep Screed vs. Plaster Stop
This is a common point of confusion. Should you use a Weep Screed (with holes) on the vertical leg, or a Plaster Stop (solid metal)?
While a Plaster Stop is technically acceptable for the vertical segment (since water falls down it, not out of it), we recommend continuing the Weep Screed profile.
Why?
1. Aesthetics: It maintains the same visual depth (7/8") and shape as the horizontal sections.
2. Breathability: The holes in the vertical leg allow air circulation behind the screed, even if they aren't actively draining water.
3. The "Diagonal" Mistake
Some contractors try to save time by running the weep screed diagonally, parallel to the slope of the hill. Do not do this.
Weep screeds must be level to function efficiently. Running them diagonally can trap water in the "V" channel if the pitch isn't perfect. Furthermore, it almost always violates the code requirement for 4-inch clearance to earth at the lower end of the slope.
4. Waterproofing the Corner (The Weak Link)
The most critical failure point in a stepped installation is the Inside Corner where the upper horizontal screed meets the vertical drop.
If this joint isn't sealed, water running down the horizontal screed will pour behind the vertical screed, rotting the framing at the step.
The Fix: We fabricate custom "saddle flashings" or soldier overlaps using 60-Minute Building Paper and polyurethane sealant to ensure water from the upper level "kicks out" over the lower level.
5. Visual Impact and Grading
Stepping the screed isn't just about waterproofing; it's about grading.
You must ensure that as the screed steps down, the soil grade follows it. You cannot bury the lower step in the dirt. The 4-inch earth clearance rule applies to every single step of the foundation.
Conclusion: A Job for Pros
Vertical and stepped weep screed installations require precise metal cutting (tin snips) and complex waterproofing laps. A mistake here funnels water directly into the mudsill. If your home has a stepped foundation, ensure your contractor understands the "waterfall" drainage principle.
Last week, we shared Selecting and Purchasing Weep Screed: A Comprehensive Guide. If you are buying materials for a stepped foundation, make sure you calculate the extra linear footage for the vertical drops.