The Brick Institute of America (BIA) used to discourage the use of clear water-repellent coatings on clay brick masonry in most situations. Technical Notes on Brick Construction-7E, "Colorless Coatings for Brick Masonry," last reissued in 1987, devoted much of its two-and-a-half pages to a litany of warnings and a lengthy checklist of procedures to follow when colorless coatings are used. Last year, however, BIA officially modified its position on clear coatings, replacing Technical Notes-7E with Technical Notes on Brick Construction-6A, "Colorless Coatings for Brick Masonry." Still emphasizing proper design and construction, especially the superior moisture resistance of a drainage wall system, the new publication does not wholeheartedly endorse colorless coatings. But it does allow that, under certain circumstances, a coating may be beneficial. APPROPRIATE APPLICATIONS BIA now suggests that water-repellent coatings may be useful on brick building elements that are particularly vulnerable to moisture penetration, for example: barrier walls; chimneys and parapets; faulty drainage walls; and highly absorptive brick. INAPPROPRIATE APPLICATIONS Technical Note-6A describes the following situations where clear water repellents are unnecessary, will not help, or will harm brick masonry: effective drainage walls; walls with severe defects; freeze-thaw regions; and exterior pavements. SELECTING A COATING The water vapor transmission rate refers to the amount of water that can evaporate through the face of the masonry. According to BIA, this is the most important property to consider when selecting a coating for exterior brick masonry. BIA recommends choosing breathable coatings, which have a high water vapor transmission rate. PENETRANTS Penetrants are coatings that penetrate the substrate, usually up to 3/8 inch. Penetrants can be classified into five groups: siloxanes, silanes, silicates, methyl siliconates, and blends of these. BIA does not recommend the use of silicates or methyl siliconates on brick masonry.