Furring Strips for Rainscreen Systems: Materials, Sizing & Installation

How to select and install furring strips that create effective drainage and ventilation behind your cladding — with a focus on the products that save labor on the job site.

A rainscreen is the air gap between your cladding and your water-resistive barrier (WRB). That gap — typically 3/8" to 3/4" — allows bulk water to drain down and out, and air to circulate and dry the wall assembly. Without it, moisture trapped between the cladding and the WRB has nowhere to go. The result is rot, mold, and premature cladding failure.

The furring strip is what creates that gap. Choosing the right material, thickness, and attachment method determines whether your rainscreen actually works or just adds cost without performance.

Why Every Exterior Wall Needs a Rainscreen Cavity

Building science has established that even the best-installed cladding leaks. Wind-driven rain pushes water past siding joints, around window trim, and through nail penetrations. In a wall without a rainscreen, that water sits against the WRB and sheathing, creating sustained moisture exposure.

A properly detailed rainscreen cavity does three things:

1. Drains bulk water: Water that penetrates the cladding hits the WRB and runs down the back of the furring strips to weep openings at the base of the wall.
2. Promotes drying: Air movement through the cavity evaporates residual moisture from both the back of the cladding and the face of the WRB.
3. Equalizes pressure: The vented cavity reduces the pressure differential that drives rain through cladding joints. This is particularly important in high-wind coastal zones.

Furring Strip Materials: Wood vs Plastic vs Metal vs Rollable Mesh

Wood Furring Strips

Traditional wood furring — typically 1x3 or 1x4 strips of spruce, pine, or fir — is the most common rainscreen spacer in residential construction. It is cheap, universally available, and easy to cut and fasten.

• Standard sizes: 1x3 (actual 3/4" x 2-1/2") and 1x4 (actual 3/4" x 3-1/2"). These provide a 3/4" cavity depth.
• 1/2" options: Some lumber yards carry 1/2" x 3" cedar or PT strips. These are harder to source and less consistent in dimension, but provide the minimum cavity depth accepted by most codes.
• Advantages: Low material cost ($0.15 to $0.40 per linear foot), easy to nail through, provides solid backing for cladding attachment.
• Disadvantages: Absorbs moisture and can rot over time (even pressure-treated), inconsistent dimensions, creates thermal bridging through the cavity, labor-intensive to cut and install piece by piece.

Plastic and Composite Furring Strips

Manufactured plastic furring strips (like Cor-A-Vent SV-3 or similar products) solve the rot problem entirely. They are typically made from recycled HDPE or polypropylene and come in consistent dimensions.

• Advantages: Will not rot, consistent dimensions, lightweight, some products include integrated bug screen mesh.
• Disadvantages: Higher material cost ($0.60 to $1.20 per linear foot), requires pre-drilling or special fasteners, limited availability in some regions, still requires piece-by-piece installation.

Metal Furring (Hat Channel)

Metal hat channel — typically 7/8" deep galvanized steel — is common in commercial construction and increasingly used in residential mid-rise. It provides a non-combustible rainscreen cavity with high compressive strength for heavy cladding.

• Advantages: Non-combustible (required for Type III and Type IV construction), high load capacity, consistent dimensions, will not rot.
• Disadvantages: Significant thermal bridging (steel conducts heat 400x faster than wood), higher cost, requires metal screws and specific fastening patterns, harder to cut and modify on site.

Rollable Drainage Mat (Keene Easy Fur)

This is where the industry is heading for residential and light commercial walls. Keene Easy Fur is a rolled, entangled-filament polymer mat that creates a consistent drainage cavity without individual furring strips.

• How it works: Keene Easy Fur is a 3-dimensional polymer mesh, typically 1/4" to 3/8" thick, that rolls out over the WRB like a house wrap. It creates thousands of drainage channels across the entire wall surface, not just at the furring strip locations.
• Cavity depth: Approximately 1/4" to 3/8" depending on the product variant. This is less than traditional furring but provides continuous drainage across 100% of the wall surface rather than only at the strip locations.
• Installation speed: A crew can roll out and staple Keene Easy Fur in a fraction of the time it takes to cut, level, and nail individual wood strips. On a 2,000 sq ft wall, the labor savings can be 4 to 6 hours.
• Cladding attachment: Cladding fasteners (siding nails) pass through the mat into the sheathing or studs. The mat compresses locally at the fastener point but maintains drainage channels everywhere else.

1/2 Inch vs 3/4 Inch Furring: Which Do You Need?

This is the most common question contractors ask about rainscreen detailing. The answer depends on your code jurisdiction, cladding type, and climate zone.

General guidance: Use 3/4" furring in climate zones 4A and higher, in areas receiving more than 40 inches of annual rainfall, and behind reservoir claddings (brick, stucco, wood). Use 1/2" furring (or rollable drainage mats like Keene Easy Fur) in drier climates and behind non-reservoir claddings (vinyl, fiber cement with back-priming).

Spacing and Layout

Vertical Furring (Horizontal Cladding)

When the cladding runs horizontally (the most common residential siding orientation), furring strips run vertically. This creates vertical drainage channels and provides nailing lines for the horizontal siding.

• Spacing: Align furring strips with studs, typically 16" on center. If the cladding requires closer nailing (some fiber cement manufacturers require 12" or less), add intermediate strips.
• Width: Use at least 1-1/2" wide strips at each nailing line. Wider strips (2-1/2" to 3-1/2") are easier to hit with siding nails.
• Top and bottom: Leave the bottom open (no furring strip across the base) to allow water to drain out. Install an insect screen at the bottom opening. At the top, leave a 1/2" gap or install vented soffit trim to allow air to exit the cavity.

Horizontal Furring (Vertical Cladding)

When cladding runs vertically (board-and-batten, vertical cedar), furring strips run horizontally. Water drains by running down the face of each horizontal strip to the one below it, in a cascading path.

• Spacing: 16" to 24" on center vertically. Closer spacing improves cladding support; wider spacing improves drainage.
• Ventilation: Horizontal furring blocks vertical air movement in the cavity. To maintain ventilation, either use furring strips with gaps between pieces (leave 1" gaps every 4 feet) or use a product like Keene Easy Fur that provides continuous drainage and ventilation in all directions.

Fastening Through Exterior Insulation

On walls with exterior continuous insulation (mineral wool, rigid foam), furring strips must be long-screwed through the insulation into the studs or structural sheathing. This is where fastener engineering matters.

• Screw length: Furring strip thickness + insulation thickness + sheathing thickness + 1.5" minimum penetration into the stud. For 3/4" furring over 2" mineral wool over 7/16" OSB: 3/4 + 2 + 7/16 + 1.5 = approximately 4-11/16". Use 5" screws.
• Screw type: #10 or #12 structural wood screws. Self-drilling tips are recommended for efficiency. GRK RSS or SPAX PowerLag screws are common choices.
• Spacing: Typically 12" to 24" on center along each furring strip, depending on cladding weight. Heavier cladding (wood shingles, thin stone) requires closer fastener spacing. Consult the fastener manufacturer's load tables for pull-through resistance in the specific insulation material.
• Washers: For heavy cladding over thick insulation, consider using insulation washers under the screw head to prevent pull-through of the furring strip through the insulation.

Building Code Requirements for Rainscreen Cavities

United States (IRC / IBC)

The 2021 IRC Section R703.1.1 introduced requirements for drainage space behind cladding in specific climate zones and conditions. Key provisions:

• Minimum 3/16" drainage space required behind absorptive claddings (stucco, thin brick, adhered stone) in climate zones 1A through 8
• Non-absorptive claddings (vinyl, metal, fiber cement) may not require a drainage space depending on the WRB system
• Drainage space must include a means of drainage at the bottom and ventilation at the top

Canada (NBC / Provincial Codes)

Canadian codes have been more aggressive on rainscreen requirements:

• BC Building Code requires a minimum 10 mm (3/8") rainscreen cavity behind all claddings in coastal climate zones
• The National Building Code of Canada (NBC 2020) includes provisions for drainage and ventilation behind cladding in all climate zones
• Ontario Building Code (OBC) requires vented and drained cladding in many assemblies under SB-12

Insect Screening at Rainscreen Openings

Every rainscreen cavity opening — top and bottom — must be screened to prevent insect entry. Wasps, carpenter ants, and other insects will colonize unscreened cavities within the first season. Use corrosion-resistant screen with openings no larger than 1/16" (stainless steel or fiberglass mesh). Products like Cor-A-Vent SV-5 include integrated insect screening and are designed to fit at the base of rainscreen cavities.

Choosing the Right Product for Your Project

• Budget-conscious residential (vinyl or fiber cement siding): Keene Easy Fur rollable drainage mat. Fastest install, adequate drainage, lowest total installed cost.
• Standard residential (wood or fiber cement siding, moderate rain): 3/4" x 2-1/2" wood furring strips (pressure-treated or cedar), 16" OC aligned with studs.
• High-performance residential (Passive House, Net Zero): 3/4" wood furring over continuous exterior insulation, with careful air sealing at all penetrations.
• Commercial / mid-rise (non-combustible required): Galvanized steel hat channel, 7/8" depth, with thermal break clips to reduce thermal bridging.
• Heavy cladding (real brick, stone veneer): 3/4" or 1" engineered furring systems with structural brackets rated for the cladding weight.