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Indoor airPLUS

Technical Guidance to the Indoor airPLUS Construction Specifications

1. Moisture Control

Sections 1.1 - 1.4: Water-Managed Site and Foundation

BEST PRACTICE: Crawl Spaces in Flood Zones

Detailed Illustrations: Best Practice Techniques

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Crawlspace/Flood Zone: Foam Board-insulated Floor Deck

Crawlspace/Flood Zone: Foam Board-insulated Floor Deck

Crawlspace/Flood Zone: Vented Crawlspace with "Flood Vents"

Crawlspace/Flood Zone: Vented Crawlspace with Flood Vents

Crawlspace/Flood Zone: Access Hatch Beneath Tub

Crawlspace/Flood Zone: Access Hatch Beneath Tub


Homes subject to flooding present unique challenges for controlling moisture and mold after such an event. "Conditioned" crawl space designs are not appropriate for homes in flood zones because they have no outside air vents in the perimeter walls to provide for drainage of flood waters. Their design generally makes it difficult to obtain timely and complete drying after flooding.


The walls of crawl spaces in flood zones should have flood vents that allow the transfer of air and allow water to drain out of the crawl space once flood waters have receded. The crawl space floor still should be designed as described in Specification 1.2, but the floor (whether a thin concrete slab or polyethylene) should be sloped towards the flood vents to lead water to their bottom edge. To enable proper drainage, the grade of the crawl space floor at the bottom of the vents should be at least 8 in. higher than the finish grade outside of the crawl space.


International Residential Code for One- and Two-Family Dwellings, 2009 , Section R322 Flood-resistant Construction, R322.2.2, Enclosed area below design flood elevation. Obtain a copy of the Codes at www.iccsafe.org/Store .

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