Concrete Unit Masonry
Use this 3-part SimpleSpecs master specification to specify concrete unit masonry construction, either load-bearing, non-load-bearing, or veneered applications.
Concrete masonry is composed of Portland cement, aggregate, water and possibly additives that improve the properties of the masonry, including lowering water absorption. Concrete masonry can be used in load-bearing, non-load-bearing, and veneered assemblies. Exposed faces can be standard smooth finish or custom finishes such as split or ground face or glazed.
Load-bearing and non-load-bearing concrete masonry typically include both horizontal and vertical reinforcing. Since it does not typically include a weep drainage network it can be susceptible to moisture infiltration when exposed to the weather.
What is a weep drainage system?
Masonry veneer is placed over other masonry backup or exterior sheathing. This type of masonry construction allows for installing a weep drainage system consisting of a weather barrier placed on the backup or sheathing, an air space, base flashings, and weeps.
A cavity mesh prevents mortar from clogging the weeps. Flexible ties should be used to secure the backup construction veneer, allowing differential movement.
What is efflorescence?
Most concrete masonry is susceptible to efflorescence, a condition in which moisture that enters the masonry is drawn to the exterior surface upon evaporation, bringing salts that exist within the masonry to the surface, where they are deposited as a white powder. Efflorescence can be easily removed using a specialty cleaner if caught early. Efflorescence tends to decrease over time as the salts decrease and shows up worse on darker surfaces.
For assistance in selecting and detailing concrete masonry, visit the National Concrete Masonry Association (NCMA) Tek Solutions Center at www.ncma.org.
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