Masonry Magazine June 2010 Page. 20
FLASHING & DRAINAGE
ture penetration in masonry construction.
The walls will become saturated as the rain fills the masonry's pores, cracks and imperfections. In this circumstance, water moves from concentrations higher to lower, more or less allowing the materials to "suck" the water right inside the wall. This is even more prominent in walls with thin and weak head joints. In older walls, in which freeze/thaw cycles have created spalling of the masonry joints, there is no resistance to water entering the wall cavity.
While the previous example shows why cracking on the wall face is a problem, I think it's important to consider where they come from, so we see how likely they are to occur. Brick units, as we are all aware, expand significantly throughout their life cycle. Concrete masonry, on the other hand, shrinks significantly throughout its service life. Both of these issues need to be coped with independently, or the wall movement will produce considerable cracking on its surface. Along the same lines, mortar mixes may tend to act much like cement block. Particularly, if too much cement or too much water is added to the mix, you will most certainly see separation cracks in the joints, due to shrinkage. Cracks also are commonly caused by differential settlement under heavy loads, and in some cases, thermal expansion where the wall is not reinforced properly.
Thermal bridging
THE "MOISTURE CONTROL HANDBOOK" defines thermal bridging as "regions of relatively high heat flow con-
SUSTAINABLE MASONRY
FOR NEW CONSTRUCTION
21st century masonry walls have become more complex with stricter code requirements, increased energy efficiency and more creative designs. The need has developed for systems or groupings of products that will function together and that have been tested to assure their compatibility and effectiveness. Hohmann & Barnard is leading the way with complete systems for various wall types that include all of the required accessories for your project. Our extensive field experience along with testing at our R&D lab allows us to offer complete systems of complementary and compatible products to give designers, contractors and building owners peace of mind.
1. H&B HB-200-X SYSTEM
2. H&B TEXTROFLASH L
AIR & VAPOR BARRIER
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4. H&B TEXTROFLASH G
(shown surface-mounte
5. H&B TERMINATION BAR
6. H&B QUADRO-VENT™
7. H&B FLEX-FLASH DRIP
8. H&B TRANSITION MEME
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