Under-deck mesh belongs on the vertical plane to grade, not under the boards
installation-mistake
Screening laid horizontally under deck boards does not close the ember path from the side. For decks with a walking surface 4 feet or less above the ground, the IBHS Wildfire Prepared Home technical standard requires noncombustible corrosion-resistant mesh with openings not exceeding 1/8 inch, fully enclosing the outer edge of the deck from the walking surface to the ground. Above 4 feet the standard sets other requirements for the space, so read the height first.
FA Exhibit DET-005. Under-deck mesh — outer edge versus under the boards. After IBHS Wildfire Prepared Home technical standard and FEMA P-737. Illustrative — not a construction document. Verify with your building official. CC BY 4.0.
Section 2.1.5.4 Underneath an Elevated Deck. Decks with a walking surface of 4 feet or less shall be enclosed with noncombustible, corrosion-resistant mesh; openings shall not exceed 1/8 inch and shall fully enclose the outer edge of the deck from the walking surface to the ground.
Under-deck mesh belongs on the vertical plane to grade, not under the boards. FireApproved. https://fireapproved.com/findings/under-deck-horizontal-mesh/. As of 2026-08-23.
