Written by Stucco Champions — Southern California’s Authority on Exterior Plastering.
The Defense Line: A Technical Guide to Stucco Paper (Grade D)
There is a saying in the trade: "The stucco is for looks; the paper is for leaks."
Because stucco is a porous reservoir that absorbs water, the Weather-Resistive Barrier (WRB) behind it is your home's only true defense against rot. However, confusion surrounds the different "grades" and "layers" required by code. This guide demystifies 10-Minute vs. 60-Minute paper and explains why the "Two-Layer Rule" is non-negotiable in California.
1. The Two-Layer Code Requirement
The most common inaccuracy found online is the idea that a single layer of paper is sufficient.
According to the California Residential Code (CRC R703.7.3) and IBC, if you are applying stucco over wood-based sheathing (Plywood or OSB), you generally must install:
- Layer 1: A base water-resistive barrier.
- Layer 2: A "sacrificial" layer that separates the stucco from the first layer.
Stucco bonds aggressively to paper. If you use only one layer, the stucco will fuse to it. When the stucco cracks (which it will) and water enters, it has a direct path to the wood. The second layer creates a bond breaker, allowing water to drain down between the two sheets and out the weep screed.
2. Understanding the Ratings (ASTM D779)
Building paper is rated by "Minutes." This is based on the ASTM D779 "Boat Test," which measures how long it takes for moisture to permeate the paper.
10-Minute Grade D Paper
This is the standard minimum code paper. It is thin, lightweight, and economical.
The Drawback: In wet coastal environments like Huntington Beach or Newport, standard 10-minute paper can degrade quickly if the stucco remains saturated ("reservoir effect"). We rarely recommend this for high-end custom homes.
60-Minute "Super Jumbo Tex"
This is the Stucco Champions Standard. It is significantly heavier, containing more asphalt saturation.
The Benefit: It offers superior holdout against heavy rain and resists tearing during lath installation. While it costs more, it is cheap insurance for your framing.
3. Product Formats: Single-Ply vs. Double-Ply
Do not confuse "Double-Ply" paper with the "Two-Layer" code requirement.
- Single-Ply Rolls: A roll containing one sheet of paper. To meet code over plywood, the crew must wrap the house twice.
- Double-Ply (2-Ply) Rolls: Manufacturers like Fortifiber (Jumbo Tex) create rolls that unspool two distinct layers of paper at once. [Image of 2-ply Jumbo Tex installation] This allows contractors to meet the two-layer code requirement in a single pass, ensuring proper overlap and reducing labor.
4. Housewraps (Tyvek) vs. Building Paper
Can you use Tyvek behind stucco? Yes, but with a major caveat.
Stucco acts like a surfactant (soap), which can break down the surface tension of certain plastic housewraps. Furthermore, stucco will bond to Tyvek, nullifying its drainage capability.
If you use Tyvek or a similar housewrap as your primary air/water barrier, you MUST install a layer of Grade D paper (or felt) over it. The paper protects the Tyvek from the cement and creates the necessary drainage gap.
5. Stucco Champions Recommendation
For the longest-lasting exterior in Southern California, we recommend avoiding the bare minimum.
- Best Practice: Two layers of 60-Minute Grade D Paper.
- Alternative: A "Hybrid" system with a high-performance housewrap (like Tyvek StuccoWrap) covered by a layer of 60-Minute paper.
Last week, we explored what happens when waterproofing fails in our guide: Comprehensive Guide to Stucco Crack Repair: Options and Considerations. If you are seeing moisture damage, start there.