The following are frequently asked questions
addressed to clay brick manufacturers:
     
  Q: What is the difference between a clay brick and a calcite brick? 

A:  A clay brick is manufactured by forming natural clays into a brick shape and firing the shape in a kiln at temperatures exceeding 1000ºC.  The clay undergoes a ceramic transformation into a permanent brick, which is colourfast.  Calcite is another term for concrete brick, moulded from concrete and coloured with pigments.

 
Q. Why is there an airspace behind brick walls? 

A. The airspace is part of the rainscreen wall system, a triple protection layer against moisture penetration.  Any wind-driven rain that finds its way through the brick wall will drain down the inside of the cavity and is directed out by the base flashing through the weepholes.  The cavity is ventilated top and bottom to allow air circulation and drying.  The third layer of protection is the building paper on top of the sheathing over the framing.  This wall system is considered by the National Research Council of Canada to be the best possible wall system.

 
Q.  What is that white powder that appears occasionally on brick walls?

A. This is called efflorescence and is a deposit of soluble salts. Although unsightly, it is usually easily brushed or washed off.  Often, efflorescence will occur on newly built walls as they dry out ("new building bloom").  Recurring efflorescence can be a cause for concern in that it indicates moisture in the wall which can ultimately cause deterioration of the wall system.  Common sources of moisture include leaking roofs or downspouts, sprinkler systems, runoff from horizontal surfaces, and interior moisture leaking through the air/vapour barrier.
See BIA Technote 23A for further information.

 
Q. What is a good specification for residential brickwork?

A. The general requirements for good masonry practice are set out in section 9.21 of all provincial building codes.  At a minimum, the clay brick should comply with grade SW (severe weather) of CSA A82.1.  The specification should also identify the manufacturers' names, colour, texture and size of brick.  The recommended cleaner for that type of brick should be included (ask the manufacturer).  The specification should identify the type of mortar (generally Type N for veneer brickwork), the style of joint (e.g. concave tooled).