How to Build a Block Wall with Natural Stone Veneer
 

  
 
  
 
 Block walls, constructed of concrete masonry units (CMU), are most common in
 the residential arena as home
 foundations.
 In commercial settings, and a growing number of residences, CMU walls are
 also used to frame exterior walls. These exterior walls offer
 strength,
 durability, and quite often, a backdrop for brick or stone veneers.
 
 
 
 In the commercial arena, most veneers are made of brick because of its
 uniformity and relative ease of installation over a large surface area. A
 larger percentage of residential
 homes prefer
 natural stone veneer because of its aesthetic and individual appeal.
 Block walls covered with natural stone veneer is significantly more
 expensive than other types of cladding, but the smaller surface area --
 usually limited to the front or street side of the house -- creates an
 affordable project for homeowners as well as adding substantial resale value
 to the home.
 
 
 
 Covering a block wall with natural stone veneer does require some extra
 considerations, mostly due to the weight of the stone itself. A footing must
 be poured beneath the wall, as per usual, but a ledge must be created to
 support the veneer. Stone veneer is typically about four inches thick. The
 veneer ledge is designed to be slightly recessed from the finished stone
 edge and should be equipped with a metal drip edge as part of a flashing
 system to vent air and moisture from behind the veneer.
 
 
 
 As the block wall is constructed, metal strips are installed at regular
 intervals, set in the mortar between CMU blocks. These strips, often called
 brick ties, are designed to hold the veneer to the block wall and prevent it
 from tipping or collapsing.
 

 
 
 *Given these two additions, the block wall to be covered by natural stone
 veneer is generally built as follows:*
 
 
 
 l  Footing is poured, taking into account several structural considerations
 including the veneer ledge.
 
 A  Block wall is constructed atop the footing, complete with steel
 reinforcing bars, mortar and metal strips.
 
 l  A vapor or weather barrier is first applied to bare block wall,
 overlapping the flashing system at the base of the wall; that flashing
 consists of a metal drip edge, base metal flashing (running at least 8" up
 the block wall), and a drainage mat with weep holes for condensation
 run-off. (Natural stone is naturally porous, which is why the weather
 barrier is necessary.) In some applications rigid, foam insulation is
 installed beneath the block wall and veneer.
 

 And  Finally, the natural stone veneer may be installed.
 
 
 There are man-made stone veneers which are thinner, lighter, and easier to
 install. From a distance these veneers have the exact look of natural stone
and thus have grown in popularity in recent years as manufacturers perfected
 the art of imitation. Still for many there is no replacing the natural look
 and feel of real stone. Whereas once natural stones comprised the entire  wall structure, that model is simply too inefficient for the modern home;
 hence the rise and continued dominance of natural stone veneers.
 

 by Dan Harding