Water Resistant Membrane Air Gap Under Siding

The exterior face of the foam sheathing is typically the water control layer for the assembly and we need an air gap between it and the stucco cladding to drain the rainwater penetrating the stucco downwards and outwards preventing the build up of hydrostatic pressure.

Water resistant membrane air gap under siding.

Hardiewrap weather barrier is installed over the sheathing beneath the exterior siding to reduce water and air infiltration. 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. That gap in a rain screen doesn t need to be significant just enough for water to drain and air to rise. Water holdout air penetration resistance and tear resistance.

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. View the test results. This intersection is critical. Typical housewraps provide only a water resistant barrier which can trap water behind claddings.

How much of an air gap do you need. A way to escape sounds logical but couldn t the gap become an open invitation for termites and exterior vapor as well. 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. Hydrogap s drainage space removes 100x more bulk water while acting as a water resistant barrier.

The solution is to include an air gap between the wrb and the back of the siding. Carefully detail the area at the bottom of the wall where the sill connects to the foundation. Should wood siding necessarily have an air gap between it and the wall sheathing behind it in a cold climate. Flashing membranes are now widely used to prevent water leakage around windows and doors and other trouble spots on walls.

It s a little like an old fashioned single wall tent. 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. 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. In independent tests hardiewrap weather barrier outperformed its nearest competition in each of these categories.

The argument for it that it allows inadvertent moisture from interior vapor rain etc. The tent won t leak until you touch it from the inside with your finger. A 1 inch air gap is needed behind brick veneer as required by the 2009 international residential code irc baechler et al. Many builders have turned to huber s zip system sheathing a type of osb with a coating of resin impregnated kraft paper.