What is house wrap and do I need it?

House wrap is a weather-resistive barrier (WRB) installed on the exterior sheathing (the plywood or OSB under your siding). It blocks liquid water and wind from reaching the wall framing while allowing moisture vapor to escape from inside the wall. It is required by building codes on virtually all new construction (IRC Section R703.2). Benefits: prevents water damage, rot, and mold in the wall cavity, reduces air infiltration (drafts and energy loss by 10-20%), and protects the structural integrity of the framing. If you are building new, re-siding, or doing a major renovation: house wrap is required and essential.

What is the best house wrap?

For standard residential construction: Tyvek HomeWrap (woven polyethylene) is the industry standard. It has excellent water resistance, high vapor permeability (allows moisture vapor to escape), and proven long-term durability. Cost: $0.15-$0.25/sq ft. For maximum performance: fluid-applied WRB ($0.50-$1.50/sq ft) or self-adhered membrane ($0.75-$2.00/sq ft) provide superior air sealing and water resistance (no seams to fail). These are increasingly used on high-performance and energy-efficient homes. The most critical factor: proper installation. A perfectly installed inexpensive house wrap outperforms a poorly installed premium product.

How do you install house wrap?

Start from the bottom of the wall. Install horizontal courses of house wrap (the roll unrolls horizontally). Each upper course overlaps the lower course by at least 6 inches (water sheds downward). Staple or cap-nail the wrap to the sheathing. Tape all seams with manufacturer-approved seam tape. Integrate the wrap with proper window and door flashing (the most critical detail). Seal all penetrations (pipes, wires, vents). Avoid reverse laps (where water could flow behind the wrap). For best performance: install a rain screen drainage gap (1/4 to 3/4 inch) between the wrap and the siding (using furring strips or a drainage mat) to allow any water behind the siding to drain freely.

Can house wrap be left exposed?

House wrap should not be left exposed for extended periods. Most manufacturers recommend covering it with siding within 3-6 months of installation. UV exposure degrades house wrap over time (Tyvek is rated for 120 days of UV exposure; some wraps are rated for up to 6 months). Extended UV exposure reduces the wrap's water resistance and tensile strength. If construction delays are expected: choose a UV-stabilized wrap with a longer exposure rating. Fluid-applied and self-adhered WRBs typically have longer UV exposure ratings (up to 12 months) than fabric wraps.

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Siding & Exterior

House Wrap Guide: Types, Installation & Why It Matters

Lumberama Editorial Team, Building Envelope & Moisture Control Specialists Jul 29, 2026 12 min read

What Is House Wrap

House wrap is a weather-resistive barrier (WRB) installed on the exterior sheathing of a building, underneath the siding. It serves two critical functions: it blocks liquid water from reaching the sheathing and framing (preventing rot, mold, and structural damage), and it blocks air infiltration (reducing drafts and energy loss). At the same time, it allows water vapor to pass through from inside to outside (preventing moisture from being trapped inside the wall cavity). Think of it as a one-way valve: water and wind stay out, but moisture vapor can escape. House wrap is required by building codes (IRC Section R703.2) on virtually all new construction and major renovations.

Types

Woven polyethylene (Tyvek HomeWrap): The most common and recognized brand. A spunbonded polyethylene fabric. High water resistance, high vapor permeability, and excellent durability. The benchmark against which other house wraps are measured. Cost: $0.15-$0.25/sq ft.

Non-woven polypropylene: Similar performance to Tyvek. Brands: Typar, VaproShield. Often less expensive. Cost: $0.10-$0.20/sq ft.

Perforated house wrap: Polyethylene with micro-perforations. Less effective at air sealing (the perforations allow some air through). Lower water resistance than non-perforated wraps. The least effective type. Cost: $0.08-$0.15/sq ft.

Fluid-applied WRB: A liquid membrane sprayed or rolled directly onto the sheathing. Creates a seamless, monolithic barrier (no seams or joints to fail). Excellent air sealing and water resistance. More expensive but superior performance. Used increasingly on commercial and high-performance residential projects. Cost: $0.50-$1.50/sq ft.

Self-adhered membrane: A peel-and-stick membrane applied directly to the sheathing. Creates an air-tight, water-tight barrier. Superior performance. Used on high-performance homes and in detail areas (around windows, doors, and penetrations). Cost: $0.75-$2.00/sq ft.

Installation Best Practices

Proper installation is critical (a poorly installed house wrap can actually trap water and cause more damage than no house wrap at all). Key principles:

Start from the bottom: Install house wrap in horizontal courses, starting at the bottom of the wall. Each upper course overlaps the lower course by at least 6 inches (like shingles, water flows down and over the lower course).

Tape all seams: All horizontal and vertical seams must be taped with manufacturer-approved tape (not generic tape). Untaped seams allow water and air infiltration.

Window and door flashing: This is the most critical detail. Integrate the house wrap with proper window and door flashing (sill pan flashing, side flashing, and head flashing) so water is directed away from the opening and onto the house wrap below. Improper window flashing is the number one cause of water intrusion in walls.

Seal all penetrations: Every penetration (pipes, wires, vents, hose bibs) must be sealed with appropriate flashing or sealant.

Avoid reverse laps: If a seam allows water to flow behind the wrap (instead of shedding over the lower course), water gets trapped behind the wrap.

Provide a drainage gap: Best practice (and required in some climates): install a rain screen (a 1/4 to 3/4 inch gap between the house wrap and the siding) to allow any water that gets behind the siding to drain freely. This can be a mesh drainage mat, furring strips, or a textured house wrap (like Tyvek DrainWrap).