Tuesday, June 19, 2012

Water Water Everywhere

Water is nature’s universal solvent. We all know that its size (volume) changes dramatically when transitioning between vapor, liquid, and ice. But what you probably don’t know, or at least haven’t thought about, is its specific effects on differing building materials.
Concrete and brick are porous by nature, acting as sponges and over time expanding. They are also very susceptible to the freeze-thaw cycle, with parts of the material cracking and chipping off over several seasons. If this type of expansion occurs at the top of a building, imagine the potential safety concerns for those walking below! 

Water can cause corrosion between differing metals adjacent to one another. This then promotes electrolysis, which expands one of these metals and forces surrounding materials (such as concrete) to crack, allowing even more water penetration. Ultimately entire sections of the metal reinforcement to a building can be fully exposed to the elements.

Water poses a big threat to wood. Wood’s porous cellular structure is a great incubator and food source for fungus. As fungus grows, it removes cellular material, leaving a brittle structure and ultimately resulting in dry rot. Going through wet and dry spells is actually worse for wood than when it is being constantly exposed to a damp environment.

Fiberglass insulation is also strongly impacted by water exposure. Normally the glass fibers create air pockets that resist heat flow. The more void air space, the higher the energy efficiency of the insulation. But when exposed to water, this ability to resist heat transfer is lost.
Typical weak points for water penetration are window perimeters, transitions between materials, expansion joints, joints in metal through-wall flashing, barrier wall systems, and roof to rising wall conditions.

Without proper enclosure design, construction and diligent maintenance, buildings will fail under water’s touch. While your community buildings may not be “proper” now, be aware of the following tips when having repairs or upgrades conducted:

  • Do not rely on a sealant as the only line of defense. Use a sheet membrane to bridge the gap between materials or adjacent systems.
  • Lap materials so that they shed water.
  • Provide a robust backup waterproofing system that will drain accumulated moisture out of the exterior walls. Provide ventilation for the drainage cavity so that the materials that become wet from incidental moisture intrusion can dry out.
  • Provide a slope to drain water off horizontal surfaces and projections such as windowsills, stone bands, metal flashing, and roof edge coping.

Remember: Proper maintenance is key to the durability of your buildings. By performing a comprehensive annual survey of the building envelope systems, the safety of your owners and guests can be preserved from the effects of water.

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