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Moisture Barriers & Drainage
Delta Moisture Barrier Systems
The complete Delta line of dimpled membranes, ventilated rainscreens, and foundation drainage boards — engineered to keep water out of walls, floors, and below-grade structures.
Delta by Cosella-Dörken is a building-envelope system for controlling water at every level of a structure. This collection brings the full range together: Delta MS, the below-grade dimpled membrane for foundation walls; Delta FL, the dimpled membrane for slab-on-grade floors; Delta Drain drainage composites for high-flow foundation and plaza work; and the Delta Dry ventilated rainscreens for stucco, stone, and siding — plus every tape, flashing, fastener, and sealant needed to finish the job. Every item on this page ships free.
The Delta Moisture Barrier System
Delta by Cosella-Dörken is a building-envelope system for controlling water at every level of a structure — below-grade foundations, slab-on-grade floors, rainscreen walls, and pitched roofs. Each membrane targets a specific assembly, and the tapes, flashings, and fasteners carry across the whole line.
Whether you're detailing a below-grade waterproofing membrane, a slab-on-grade vapor barrier, or a ventilated rainscreen behind stucco, the Delta system gives you a proven dimple-board approach — and every item on this page ships free.
Choosing the Right Delta Membrane
The Delta line is organized by where the moisture problem is. Match the product to the assembly — a below-grade wall, a slab-on-grade floor, a drainage-heavy deck, or a stucco wall each calls for a different membrane.
Below grade
Foundation walls
Delta MS is the classic dimpled membrane, or dimple board, for foundation walls. Its air-gap dimples hold soil off the wall and give water a clear path to the footing drain — a below-grade waterproofing membrane and foundation drainage membrane in one sheet.
Slab on grade
Under-floor moisture
Delta FL is the dimpled membrane for slab-on-grade floors. It creates a capillary break and drainage void beneath the slab, acting as a slab-on-grade vapor barrier that keeps ground moisture from wicking into finished floors.
High flow
Drainage composites
Delta Drain composites pair a dimpled core with bonded filter fabric for heavy-duty foundation and plaza-deck drainage — the choice when the job needs more flow than a standard drainage mat provides.
Walls above grade
Ventilated rainscreens
The Delta Dry family is a ventilated rainscreen for stucco, stone, and siding. Delta Dry Stucco & Stone and Delta Dry & Lath give a drainage-and-drying gap behind cladding — the proven stucco rainscreen approach.
Delta Membrane Types
Every product here is part of the same Delta system, so tapes, flashings, and fasteners carry across the line. Use this table to match the membrane to its place on the building.
| Product | Where It Goes | What It Does |
|---|---|---|
| Delta MS | Below-grade foundation walls | Dimpled membrane air gap; below-grade waterproofing and drainage |
| Delta FL | Under slab-on-grade floors | Capillary break and drainage void; slab-on-grade vapor barrier |
| Delta Drain | Foundations, plaza decks, planters | High-flow drainage composite with bonded filter fabric |
| Delta Dry | Behind stucco, stone, siding | Ventilated rainscreen; drainage and drying gap |
| Delta Trela | Pitched metal roofs | Separation and drainage underlayment |
Complete the System
A dimpled membrane only performs as well as its seams and terminations. This collection includes the accessories that finish a Delta installation correctly, so the whole assembly stays under one warranty-friendly system.
Tapes
Multi-band and moisture-proof tapes for lapping and sealing sheets.
Flashing & sealant
Delta LFS liquid flashing and sealant for penetrations and corners.
Fasteners
Grip, screw, and T-fasteners for reliable mechanical attachment.
Terminations
Mold strips, bug screens, and cold-weather adhesive for clean finishes.
Delta Membrane FAQ
How do you install a dimpled membrane on a foundation?
Delta MS is installed dimples-against-the-wall, run vertically, and fastened along the top edge with grip or screw fasteners. Sheets overlap at the dimpled edge and the top is capped with a molding strip so backfill can't get behind the membrane. The bottom is left open at the footing so drained water reaches the perimeter drain. Follow Cosella-Dörken's current installation guide for your specific detail.
What is the difference between Delta MS and Delta Drain?
Delta MS is a single dimpled membrane that provides an air gap and drainage plane against a foundation wall. Delta Drain is a drainage composite — a dimpled core bonded to a filter fabric — designed for higher flow and applications like plaza decks and planters. For a typical residential foundation, Delta MS is the standard choice; step up to Delta Drain when the design calls for greater drainage capacity.
Is a dimpled membrane a vapor barrier?
Under a slab, Delta FL functions as a slab-on-grade vapor barrier and capillary break. On a foundation wall, a dimpled membrane like Delta MS is primarily a drainage and protection layer that works alongside your waterproofing — it is not a substitute for a dampproofing or waterproofing coating where one is required by code. Check your local requirements and the manufacturer's specifications for the assembly.
What is a ventilated rainscreen and when do I need one?
A ventilated rainscreen is a drainage and drying gap between the weather-resistant barrier and the cladding. The Delta Dry family creates that gap behind stucco, stone, and siding, so any water that gets past the cladding can drain and the wall can dry. A stucco rainscreen is widely recommended in wet climates and is required by many modern codes for stucco and adhered-stone assemblies.
Does everything on this page ship free?
Yes. Every Delta product on this page ships free on all orders. If you need volume pricing on a large quantity, use the quote request page and we'll put together a written quote.