InterNACHI Wind Mitigation cheat sheet

Wind mitigation inspection documents features that reduce wind damage for insurance premium credits; it is not a home inspection or code compliance check.

The inspection form used in Florida is the Uniform Mitigation Verification Inspection Form (OIR-B1-1802); other states may use different forms.

Inspectors must be qualified per state requirements; in Florida, licensed home inspectors, contractors, engineers, and architects may perform them.

The report must be signed and dated by the inspector, with photos verifying key features; falsifying information is fraud.

Mitigation features include roof covering, roof deck attachment, roof-to-wall connection, roof geometry, secondary water resistance, and opening protection.

Inspections are typically requested by homeowners seeking insurance discounts; the insurer sets the credit amounts.

Inspectors must not recommend repairs or suggest upgrades; only report existing conditions.

The form has sections for building code, roof age, permit information, and inspector credentials.

Wind pressure on a building increases with the square of wind speed: dynamic pressure q = 0.00256 × V² (psf, V in mph).

Wind loads are both inward (pressure on windward walls) and outward (suction on leeward walls and roof).

Roofs experience uplift due to negative pressure; corners and edges have higher suction than the field.

Openings in the envelope allow internal pressurization, which can double the net uplift on roofs.

Continuous load path from roof to foundation is critical; weak links (e.g., toe-nailed connections) fail first.

Wind-driven rain can penetrate gaps and cause water damage even if the structure survives.

Debris impact can breach glazing or walls, leading to pressurization and progressive failure.

Terrain and exposure category affect wind speed; open terrain (Exposure C) has higher winds than suburban (B).

Gable end walls are vulnerable to wind; if not braced, they can collapse inward or outward.

Soffits and fascia can be lifted by wind, allowing water intrusion and loss of roof edge support.

Wall openings (windows, doors) that fail create internal pressure and increase roof uplift.

Roof overhangs create uplift; large overhangs are more susceptible.

Exterior cladding (siding, stucco) can be torn off, exposing sheathing and allowing water entry.

Continuous load path from roof to foundation must be maintained; envelope breaches can break it.

Damage often starts at edges, corners, and penetrations; these areas need special attention.

Water intrusion through envelope breaches can cause mold and structural deterioration.

Opening protection includes impact-rated glazing, shutters, panels, or reinforced doors; all openings must be protected to qualify for the highest credit.

Gable end walls must be braced to resist wind; look for diagonal bracing, sheathing, or continuous load path.

Garage doors are large openings; they must be rated for wind pressure and have proper track and reinforcement.

Entry doors should have three hinges and a deadbolt; impact-rated doors have labels indicating rating.

Windows must have labels or markings indicating impact rating or approved shutter systems.

Gable end wall construction: check for continuous sheathing, proper nailing, and connection to wall below.

Non-rated openings can be protected by shutters; shutters must be tested and labeled.

Verify that protection covers all openings, including skylights and gable vents.

Start inspection by verifying address, taking overall photos, and documenting roof covering type and age.

Roof covering types: asphalt shingles, metal, tile, concrete, or membrane; each has different wind resistance.

Look for roof covering product approval or evaluation report; it indicates wind speed rating.

Record roof covering condition: missing, cracked, or deteriorated shingles may not qualify for credit.

Roof age and permit date affect eligibility; older roofs may not qualify for certain credits.

Take photos of roof covering from ground and close-ups; include labels if available.

Document roof geometry (hip, gable, flat) and secondary water resistance (SWR) if present.

Verify roof covering meets current code if required by form; otherwise report as is.

Roof deck attachment refers to how plywood/OSB sheathing is fastened to roof framing.

Common attachment methods: 8d nails at 6" o.c., 8d nails at 12" o.c., staples, or screws.

Enhanced attachment (e.g., 8d nails at 6" o.c. or ring shank nails) may qualify for better credit.

Verify nail size and spacing by observing from attic; measure spacing and nail diameter.

Look for nail penetration through sheathing; under-driven or over-driven nails reduce capacity.

Deck attachment must be documented with photos showing nail spacing and type.

If sheathing is not visible, use a probe or remove a small section with permission.

Roof deck attachment is a key factor in wind uplift resistance; weak attachment leads to loss of roof sheathing.

Roof-to-wall connection transfers uplift from roof to walls; common types: toe nails, clips, straps, or structural screws.

Toe nails (nails driven at an angle through rafter into wall) are weakest and often fail.

Clips (metal connectors) provide better connection; straps that wrap over rafter and down wall are stronger.

Double straps (both sides of rafter) provide highest credit.

Inspect from attic: look for straps, clips, or nails; measure strap thickness and nail count.

Verify connection at all rafters/trusses; missing connectors reduce overall performance.

Document with photos showing connector type and placement.

Roof-to-wall attachment is critical for continuous load path; failure can lead to roof uplift and wall collapse.

Roof geometry types: hip, gable, flat, and combinations; hip roofs perform better in wind.

Hip roof has slopes on all sides; reduces uplift and is often credited.

Gable roof has two sloping sides and vertical gable ends; more vulnerable to wind uplift.

Flat roof has low slope; wind performance depends on edge detailing.

Roof geometry is determined by visual inspection from ground or attic; measure slope if needed.

Document roof shape with photos and sketch if necessary.

Hip roofs may qualify for better credits; verify that all sides are sloped.

Complex roofs with multiple gables and valleys may have higher wind loads; note any irregularities.

Secondary water resistance (SWR) is a layer under roof covering that prevents water intrusion if shingles fail.

Common SWR materials: self-adhered modified bitumen membrane, peel-and-stick underlayment.

SWR must cover entire roof deck, including valleys and edges, to qualify.

Verify SWR by lifting shingles or inspecting from attic at eaves; look for membrane.

SWR is often required in high-wind areas; check building code for requirements.

Document SWR with photos showing material and coverage.

SWR can reduce water damage but does not improve wind uplift resistance.

If SWR is not present, report as none; do not assume based on roof age.

Opening protection includes impact-rated windows/doors, shutters, or panels that protect against debris.

All openings (windows, doors, skylights, gable vents) must be protected to qualify for the highest credit.

Impact-rated glazing has a label indicating compliance with ASTM E1886/E1996 or Florida Building Code.

Shutters must be tested and labeled; verify they cover the entire opening and are properly anchored.

Garage doors require reinforcement or impact rating; check for label or rating.

Document each opening with photos showing protection type and label.

If some openings are unprotected, credit may be reduced; note which are protected.

Opening protection prevents internal pressurization and debris intrusion, reducing damage.

Required photos: front of house, address verification, roof covering, roof deck attachment, roof-to-wall connection, SWR, opening protection, and labels.

Each photo should be dated and labeled with location and description.

Take wide-angle and close-up photos to show context and detail.

For roof-to-wall, photograph at least three different locations; show connector type and nail count.

For roof deck attachment, photograph nail spacing and type; use a ruler for scale.

For opening protection, photograph each opening and label; include manufacturer label.

Document any limitations (e.g., areas not accessible) and note them in report.

Keep photos organized and attach to inspection form; retain copies for records.