Water-Damage and Stone Veneer

Every summer we get calls from new and existing building owners that say they smell musty odors in certain rooms or areas. The odors are worse after rain or on hot, humid days. Usually, these observations are the result of water entering through the fa?ade and wetting the sheathing and (sometimes) insulation. Although every single type of siding can be a problem if not properly installed, this article will only discuss stone veneer. This material is also called Cultured Stone, cast stone, and (affectionately by some contractors) "lick and stick" stone.

Stone veneer is extremely common and looks great. Unfortunately, the material is frequently installed incorrectly. Improper installation often results in surprising amounts of water damage and decay within the wall. Stone veneer should be installed similar to stucco, but instead builders often think of it more as brick. Brick is installed with an air barrier between the brick and the?building paper (such as Tyvek). However, stone veneer is installed directly on the building paper as is stucco. Brick is often installed over a single layer of building paper. Stone veneer must be installed over two layers of Type D building paper (preferably 30 or 60-minute rated product). Properly installed flashing details around window, doors, lights, connections between roofs and side walls, and other locations are critical.

When the building paper or flashing details are not properly installed, water seeps around or through the paper and soaks into the wood sheathing and framing. Recurring water entry can completely decay the sheathing and significantly affect the wall framing. The wetting of the wall results in a release of volatile chemicals from the building materials and the presence of mold and bacterial growth. These items can then impact air quality through both cosmetically with the release of chemical and musty odors and impact the health of sensitive occupants.

When purchasing a building with veneer siding, ensure the home inspector is aware of your concerns of potential water issues. The inspector will want to take special notice of the items below. Environmental Initiatives has specialized devices and tools to detect water damage behind veneer if a focused assessment is desired.

• Cracking of mortar between stones (see picture below). Cracking of stone at corners or at sensitive areas (see picture below). Wet sheathing will typically expand and swell, cracking the mortar and stone.
• Musty or chemical odors emanating from outlets or from around windows.
• Discoloration or deformations in wood, tile, or vinyl flooring at exterior walls.
• Water staining on the rim joists that appear to be from water running down the rim joists.

If damage is observed, the next step is to determine if the damage is localized (perhaps because of a missing piece of flashing detail) or if the damage may be widespread or in multiple locations. The following step is to remove one or more areas of the stone veneer in an area of damage to assess the installation of the building paper and to view the current extent of the decay. Air and dust testing may be completed on the interior for loose mold debris and (sometimes) for volatile chemicals if there is a concern regarding exposures to sensitive occupant.

Stone veneer, when properly installed, creates a beautiful and long-lasting fa?ade. Unfortunately, improper installation of the building paper or flashing details is rather common. If you are purchasing a building with stone veneer, or currently occupy such a building, be sure to pay close attention to the veneer and interior surfaces near walls for evidence or signs of moisture damage.

For additional questions on this topic or to arrange an assessment, please contact us at [email protected].