Masonry veneer

Masonry veneer walls consist of a single non-structural external layer of masonry work, typically brick, backed by an air space. The innermost element is usually structural, and may consist of wood or metal framing or masonry. Walls constructed in this manner have several advantages over solid masonry:

• The airspace functions as a drainage plane, allowing any water that has penetrated the veneer to drain to the bottom of the cavity, where it encounters flashing and is directed to the outside through weep holes, rather than entering the building.

• The cavity can include insulation, which is typically in the form of rigid foam, increasing the thermal performance of the wall.

• The structural framing or masonry backup can be erected first to allow the rest of the building structure to be completed concurrently with the outer veneer, rather than waiting for the entire wall structure to be completed before proceeding with the roof and upper floors.

• A masonry veneer wall can be completed in a shorter time with less labor than a solid masonry wall thus saving in cost.

• The weight of a veneer wall can be significantly less than solid masonry, resulting in economies in foundations and structural support.

Support

Because the masonry veneer is non-structural, it must be tied back to the building structure to prevent movement under wind and earthquake loads. This is usually accomplished by a means that does not interrupt the drainage plane and does not compromise cavity insulation. Brick ties are used for this purpose, and may take the form of corrugated metal straps nailed or screwed to the structural framing, or as wire extensions to horizontal joint reinforcement in a fully-masonry veneer system. Additionally, the veneer is vertically self-supporting over relatively short heights, so shelf angles or relieving supports must be provided, typically at floor edges, to transfer the weight of the veneer to the building structure. In multi-story buildings, such a system is called a curtain wall.

Materials

Masonry veneers can be made of any concrete, manufactured clay, artificial stone or natural stone product. Typically, masonry refers to individual units that are placed in a mortar bed, making a distinction with panelized products.

If a masonry veneer is used over a framed wall, sheathing and a moisture barrier are required to assure the weather tightness of the assembly.

Rain screens

A variant on masonry veneer is the rain screen veneer. Rain screens are ventilated at the top and bottom of the cavity to prevent wind-driven rain from being driven into the building by unbalanced pressure. Such systems are typically encountered in areas where blowing rain is a significant concern.

Thermal performance

Buildings with masonry veneer walls can be better at cooling down during extended periods of hot weather than framed and sided buildings - making conditions more comfortable at night during summer.

Reverse masonry veneer walls have the brickwork inside and lightweight frame and cladding outside. This has the advantage of providing the thermal mass on the inside of a building.

References

Beall, Christine (1987). Masonry Design and Detailing (2nd Edition). McGraw Hill Book Company. ISBN 0-07-004223-3.