Vapor Barrier Types for Concrete: Full Comparison

This guide covers every major vapor barrier type used under concrete slabs, how to read the specs, and a practical decision framework for your project. For a broader overview of when vapor barriers are needed and how they're installed, see our complete vapor barrier guide.

Understanding Permeability Ratings

Permeability—measured in perms—is the single most important number on a vapor barrier spec sheet. It tells you how much water vapor can pass through a material per hour per square foot per inch of mercury pressure difference.

The perm scale:

Perm Rating	Classification	Meaning
Under 0.1	True vapor barrier	Near-impermeable
0.1–1.0	Vapor retarder	Slows but doesn't stop vapor
Above 1.0	Not rated as barrier/retarder	Minimal moisture resistance

A true vapor barrier—what most flooring manufacturers and modern building codes require for enclosed slabs—has a perm rating under 0.1. Many products sold casually as "vapor barriers" are technically vapor retarders at their labeled thickness.

What this means in practice: If your flooring adhesive spec or building inspector says "vapor barrier," verify the perm rating. Using a 0.15-perm product where a 0.05-perm product is required won't be obvious during installation—but it will show up as adhesive failure or flooring damage within a few years.

Type-by-Type Breakdown

6-Mil Polyethylene

Perm rating: ~0.08–0.12 perms Cost: $0.03–0.06 per sq ft

The cheapest option and the one you'll find in bulk at any home center. Six-mil was the industry standard through the 1980s and 1990s and still technically meets the old minimum spec. The problems:

• Tears easily. Rebar chairs, workers walking on it during pour setup, and sharp gravel all puncture 6-mil. A torn barrier isn't a barrier.
• Outdated code standard. Most jurisdictions moved to 10-mil minimum. Check your local building code before specifying 6-mil.
• Marginal perm rating. Some 6-mil products test above 0.1 perms and are technically vapor retarders, not barriers.

Bottom line: Don't use 6-mil as your primary vapor barrier unless your code explicitly permits it and you have a plan to prevent punctures.

10-Mil Polyethylene

Perm rating: ~0.03–0.05 perms Cost: $0.05–0.10 per sq ft

The current baseline for residential slab on grade construction. Ten-mil is significantly more resistant to puncture than 6-mil, qualifies as a true vapor barrier at this perm rating, and meets building code requirements in most US jurisdictions.

Use for:

• Standard residential slabs (patios, driveways poured on grade)
• Garage floors where you're not planning an immediate coating installation
• Any application where 6-mil is insufficient but budget is the primary constraint

Limitations: Not rated for heated floor systems or high-moisture below-grade applications. Some flooring manufacturer specs call for 15-mil minimum.

15-Mil Polyethylene

Perm rating: ~0.01–0.03 perms Cost: $0.07–0.13 per sq ft

The upgraded standard that many codes now require as minimum for enclosed slabs. Fifteen-mil provides meaningfully better puncture resistance than 10-mil and a lower perm rating that meets stricter flooring adhesive specifications.

Use for:

• Basements and below-grade applications
• Any enclosed residential slab
• Garage floors where you plan to apply coatings within a few years
• Code-required projects that specify 15-mil

Reinforced Polyethylene

Perm rating: ~0.01–0.02 perms Cost: $0.09–0.18 per sq ft

Reinforced poly has a woven or non-woven scrim layer laminated between polyethylene sheets. The scrim dramatically increases puncture and tear resistance without adding significant thickness. Seam integrity is better than standard poly because the reinforcing layer resists separation at overlaps.

Use for:

• Applications with aggressive construction traffic (multiple trades walking on the barrier before pour)
• Projects where rebar placement is complex and creates many puncture opportunities
• Commercial and multi-family residential work where lap joint reliability matters

Note: "Reinforced" is a construction description, not a certification. Verify perm rating and check for ASTM E1745 compliance separately.

Class A Membranes (ASTM E1745)

Perm rating: Under 0.01 perms (often 0.003–0.007) Cost: $0.15–0.35 per sq ft

ASTM E1745 classifies vapor barriers in three grades: A, B, and C, based on permeance, puncture resistance, and tensile strength. Class A is the highest:

• Permeance: Under 0.1 perms (must meet this to qualify; best products are far below)
• Puncture resistance: 2,200+ grams per ASTM E154
• Tensile strength: 45+ lbf/in per ASTM D882

Common brands: Stego Wrap (15-mil Class A), Viper VaporCheck II, Raven Industries products.

Use for:

• Heated floor systems (radiant in-floor heating)
• Below-grade slabs in high-water-table areas
• Anywhere a flooring manufacturer or adhesive spec calls for Class A
• Code-required Class A specification (increasingly common in commercial construction)

Comparison Table

Type	Perm Rating	Puncture Resistance	Code Status	Cost/sq ft
6-mil poly	~0.10	Poor	Outdated in most jurisdictions	$0.03–0.06
10-mil poly	~0.04	Moderate	Meets most residential codes	$0.05–0.10
15-mil poly	~0.02	Good	Meets strict residential codes	$0.07–0.13
Reinforced poly	~0.01	Very good	Meets code + better durability	$0.09–0.18
Class A membrane	Under 0.01	Excellent	Required for heated/high-moisture	$0.15–0.35

How to Choose

For a standard patio, driveway, or shed floor: 10-mil polyethylene. This is the practical minimum that meets current code in most areas. You're not applying flooring and moisture transmission matters less.

For a garage floor: 10-mil if it's staying as bare concrete long-term. Upgrade to 15-mil or reinforced if you plan any coating within the next 5–10 years—you'll thank yourself when epoxy goes on smoothly years later.

For a basement or enclosed living space: 15-mil minimum. If your flooring spec or code calls for Class A, use Class A. The cost difference per sq ft is small relative to the total project.

For radiant heated floors: Class A membrane. No exception. The moisture-related failure modes for heated floors are severe and expensive to fix.

For commercial work: Specify Class A and verify product certification. Building inspectors in commercial contexts increasingly require documentation.

Related Pre-Pour Decisions

Vapor barrier type selection happens in parallel with other material decisions before a pour. Two related planning guides:

• When to use rebar — similar pre-pour specification question with grade, spacing, and application variables
• Ready-mix vs bagged concrete — the other major material decision for most pours

For full installation instructions—seam overlap, penetration sealing, position relative to gravel—see how to install a vapor barrier under a concrete slab.