Adhered Masonry Veneer

Adhered Masonry Veneer

Adhered masonry veneer (AMV) is usually a manufactured material made to look like natural stone and sometimes like brick. It is installed by setting the material in a mortar bed applied to wire lath placed over sheathed wood-framed walls and a water-resistive barrier, using techniques similar to those used to install stucco. AMV has been available since the 1960s, though it is most common on homes built since the mid-1980s. This material is also called artificial stone, cultured stone, and manufactured stone. Cast stone is a different product. Do not describe artificial stone as natural stone, cast stone, or brick.

Adhered veneer using natural stone is available. It is installed in a manner similar to artificial stone veneer and it can be difficult to distinguish between the two materials. The pigment layer of artificial stone may be only at the surface, so scraping a small inconspicuous area may sometimes distinguish between the two materials. Artificial stone has a more hollow sound when tapped, but this distinguishing method requires experience to use, and can yield an incorrect identification.

Adhered masonry veneer should be installed according to manufacturer’s instructions. These instructions may vary based on the manufacturer, the type of material being installed, and the location of the house.

Adhered veneers are (artificial and natural) a known problematic wall covering. Problems are usually caused by failure to install recommended flashing and sealants around penetrations such as windows and doors. Common installation guidelines include installing a backer rod and sealant around the perimeter of windows and doors, and installing header flashing above windows and doors. Problems are also caused by failure to install recommended weep screed, and failure to maintain recommended clearances between the adhered veneer and grade, and between adhered veneer and the roof. Home inspectors should carefully inspect adhered veneer installations.

Typical Defects Typical defects that home inspectors should report include:

1. inadequate clearance above grade, hard surfaces, and roof coverings,
2. absent or improperly installed weep screed,
3. blocked weep screed drain holes,
4. absent and deteriorated flashing and sealant around doors, windows, other penetrations, and at transitions between wall coverings,
5. absent and improperly installed flashing and kick out flashing at wall intersections,
6. absent, loose, and damaged stones and mortar,
7. exposed lath,
8. veneer not fully embedded in mortar (not usually visible),
9. efflorescence on stone or mortar,
10. water on stone or mortar long after rain has ceased falling.

Standards (1) IRC 2018 Section R703; (2) Masonry Veneer Manufacturer’s Association Guidelines; (3) manufacturer’s instructions.