Masonry Restoration Issues: Factors Contributing To The Deterioration Of Masonry Faade Systems In

The practice of masonry restoration engineering has evolved over the last 30 years as the inventory of mid to high-rise masonry-clad buildings ages

. New materials and techniques have been developed to provide masonry restoration professionals, contractors and building owners with repair alternatives to extend the useful life of the aging structures.

Masonry cavity walls and veneers have been in use for over a hundred years, though typically in low-rise buildings of three to four stories. Beginning in the 1930s, medium and high-rise steel and reinforced concrete framed buildings began using masonry envelopes due the availability of materials. They have, though, introduced unique challenges for masonry restoration engineers as they age.

The lack of proper design, detailing and construction methods to accommodate for differential movements between frame and masonry faade in these buildings have been identified by masonry restoration engineers as the fundamental structural flaw behind recent failures in masonry faade systems.

masonry restoration engineers have identified distinct failure mechanisms that are responsible for this common faade issue.

As previously noted, most masonry cavity and veneer facades in the early part of the 20th century were only 3 to 4 stories in height. In buildings of this stature, changes in the vertical dimensions of materials have little effect on the performance of the exterior wall system. Therefore, such changes did not, in the past, enter into design calculations. As masonry cladding for high-rise buildings became more and more common, this lack of design detail unfortunately carried over. It wasnt until masonry restoration engineers began noting the similarity of faade failures that further investigation revealed the fundamental structural forces and design issues behind these faade failures.

Reinforced concrete columns in high-rise buildings experience significant shortening (unlike steel frames) due to elastic, thermal shrinkage and creep strain, while masonry facades with brick cladding tend to expand. These diametrically opposed forces create stresses that transfer loading to the masonry facade components, causing spalling and buckling of masonry units and mortar joints. Deterioration of the masonry components as well as improperly designed or distributed ties present additional challenges for the masonry restoration engineer analyzing a faade failure.

Many other factors play into the exact expression of these material movement failures. Factors such as the size, shape and orientation of the building, the pattern of fenestration, the proximity of panels to corners, and the time of year of construction all contribute to the overall deterioration pattern of a specific facade system. One factor that masonry restoration engineers consistently contribute to the deterioration of a masonry faade system is the placement and detailing of steel shelf angles. As the shelf angles transfer loads from the frame to the cavity walls and veneer, differential movement of the individual components often leads to deterioration within the system. Depending on the shelf angle configuration, masonry restoration specialists suggest replacing the mortar joint at the shelf angle with a flexible sealant, or introducing precisely calculated gaps between the shelf and brick cladding to dissipate the load transfer between the masonry veneer and the primary building structure.

by: Joel Darras

POST COMMENT

Key success factors for an entrepreneur Factors To Consider When Handling Moving Supplies Important Factors To Consider When Choosing A Caravan Park Key factors driving Hong Kong company formations Factors Affecting Career Choices DUI Attorneys, Some Of The Genuine And Legitimate Factors To Employ Them Factors To Consider When Building Chicken Coops Chronic Prostatitis - Only Three Critical Factors Are Needed For A Cure - First Factor Know Factors Associated With High PR Link Factors To Consider While Choosing Roofing Contractors In Beaverton Oregon Murphy Beds: Five Factors You Ought to Know Spread Betting Companies - What Factors Should You Use To Choose The Right One? Factors That Help Determine Whether Liposuction Is The Best Decision