Water Resistant Membrane Air Gap Under Siding

A 1 inch air gap is needed behind brick veneer as required by the 2009 international residential code irc baechler et al.

Water resistant membrane air gap under siding.

Building america recommends a gap of at least 1 16 inch behind lap siding and a drainage space of inch between stucco and plastic house wraps to control liquid phase water penetration. Should wood siding necessarily have an air gap between it and the wall sheathing behind it in a cold climate. View the test results. If the weather barrier is tightly attached as in the case of a peel and stick membrane or is part of a rigid board product building scientists say as little as 1 16th gap provides a capillary break that will let liquid water drain out.

The argument for it that it allows inadvertent moisture from interior vapor rain etc. Water holdout air penetration resistance and tear resistance. Once you staple or fasten a membrane to a wall and pinch it between the siding and the sheathing most membranes leak. Installing a strip of self healing bituthane membrane like ice and water shield under the siding at the bottom of the wall may be a worthwhile investment.

That gap in a rain screen doesn t need to be significant just enough for water to drain and air to rise. Hydrogap s drainage space removes 100x more bulk water while acting as a water resistant barrier. Typical housewraps provide only a water resistant barrier which can trap water behind claddings. It s a little like an old fashioned single wall tent.

The tent won t leak until you touch it from the inside with your finger. Flashing membranes are now widely used to prevent water leakage around windows and doors and other trouble spots on walls. Hardiewrap weather barrier is installed over the sheathing beneath the exterior siding to reduce water and air infiltration. A way to escape sounds logical but couldn t the gap become an open invitation for termites and exterior vapor as well.

The layer beneath the siding the water resistive barrier or wrb is what will protect the plywood or oriented strand board osb sheathing from any water that sneaks in. Hydrogap has a 3 layer non woven substrate to provide superior tear water and air resistance. How much of an air gap do you need. Carefully detail the area at the bottom of the wall where the sill connects to the foundation.

The solution is to include an air gap between the wrb and the back of the siding. Sold as flashing tape flexible flashing and peel and stick window flashing these narrow rolls of rubberized asphalt membrane can solve many flashing problems if installed correctly. This intersection is critical. Many builders have turned to huber s zip system sheathing a type of osb with a coating of resin impregnated kraft paper.