Water Resistant Membrane Air Gap Under Siding

Water holdout air penetration resistance and tear resistance.

Water resistant membrane air gap under siding.

Should wood siding necessarily have an air gap between it and the wall sheathing behind it in a cold climate. Same as with osb 3 8 inch. Hardiewrap weather barrier is installed over the sheathing beneath the exterior siding to reduce water and air infiltration. Typical housewraps provide only a water resistant barrier which can trap water behind claddings.

A way to escape sounds logical but couldn t the gap become an open invitation for termites and exterior vapor as well. In independent tests hardiewrap weather barrier outperformed its nearest competition in each of these categories. 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.

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 tent won t leak until you touch it from the inside with your finger. The solution is to include an air gap between the wrb and the back of the siding. 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 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. It s a little like an old fashioned single wall tent.

A 1 inch air gap is needed behind brick veneer as required by the 2009 international residential code irc baechler et al. 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. Many builders have turned to huber s zip system sheathing a type of osb with a coating of resin impregnated kraft paper. Once you staple or fasten a membrane to a wall and pinch it between the siding and the sheathing most membranes leak.

Flashing membranes are now widely used to prevent water leakage around windows and doors and other trouble spots on walls. 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. This intersection is critical.