Choosing the right house wrap is a critical decision for long-term building performance. While traditional flat house wraps have been used for decades, changing construction methods, tighter building envelopes, and increased moisture exposure have made drainable house wraps more important than ever.
Understanding the difference between drainable vs traditional house wraps can help builders reduce moisture-related risk, improve durability, and protect the building envelope over time.
What Is a Traditional House Wrap?
Traditional house wraps are flat water-resistive barriers (WRBs) designed primarily to block bulk water while allowing some vapor permeability. They are typically installed directly against the sheathing, creating little to no space for water to drain once it gets behind the siding.
While traditional wraps can shed water, they rely heavily on perfect installation and favorable drying conditions. When moisture becomes trapped, drying can be slow — especially in colder or more humid climates.
What Is a Drainable House Wrap?
A drainable house wrap is designed not only to resist water but to actively manage it. These wraps create a dedicated drainage space between the wrap and the siding, allowing water to move downward and exit the wall assembly more efficiently.
ALTA® is a drainable house wrap that achieves this through a reinforced mesh structure made with CLAF® technology. Instead of relying on surface textures or coatings, the drainage capability is built directly into the material.
Key Differences Between Drainable and Traditional House Wraps
1. Moisture Management
Traditional wraps focus on water resistance alone. Drainable wraps add a second layer of protection by providing a path for water to escape.
In real-world conditions — wind-driven rain, snow melt, or condensation — drainage becomes critical. Without it, moisture can remain trapped behind the siding, increasing the risk of mold, rot, and sheathing damage.
2. Drying Speed
Drainable house wraps help walls dry faster by allowing gravity to move water out of the assembly. Traditional wraps depend on evaporation, which slows significantly in winter or high-humidity environments.
Faster drying equals lower long-term risk.
3. Performance Under Compression
Some drainable wraps rely on raised textures or coatings that can flatten under siding pressure. ALTA® uses CLAF® mesh, an oriented polyethylene scrim that maintains open channels even when compressed, ensuring consistent drainage performance over time.
CLAF® reinforces the wrap while preserving airflow and water movement.
4. Strength and Durability
Drainable wraps with reinforced structures tend to offer higher tear and puncture resistance than traditional flat wraps. This matters during installation, especially in windy conditions or cold weather when materials can become more rigid.
ALTA® combines drainage and reinforcement in a single structure, improving handling and long-term durability.
5. Real-World Installation Conditions
In theory, traditional house wraps can perform well. In practice, walls are exposed to:
- Fastener penetrations
- Irregular siding surfaces
- Weather delays
- Seasonal moisture swings
Drainable house wraps provide an added layer of forgiveness when conditions are less than ideal.
Why Drainage Matters More in Modern Construction
Today’s buildings are tighter and more energy efficient, but that also means they dry more slowly. As insulation improves and air leakage decreases, moisture that enters the wall assembly has fewer pathways to escape.
Drainable house wraps are designed to address this reality by combining water resistance, drainage, and breathability into a single system.
Where ALTA® Fits In
ALTA® is engineered as a two-layer drainable house wrap that pairs a water-resistant outer film with a reinforced CLAF® mesh layer. The mesh creates natural vertical drainage channels while also strengthening the wrap.
This design allows ALTA® to:
- Exceed ASTM E2273 drainage requirements
- Maintain drainage under compression
- Improve tear resistance
- Support faster wall drying
For builders evaluating drainable vs traditional house wraps, ALTA® offers a balanced solution built for real-world performance.
Choosing the Right House Wrap for Your Project
Every project is different, but understanding how a house wrap manages moisture is essential. While traditional wraps can still play a role in some applications, drainable house wraps provide added protection that aligns with modern construction demands.
When moisture management matters — and it always does — drainage makes the difference.