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Historic and existing masonry buildings have common issues that architects, engineers, conservators, contractors, and owners are often challenged with evaluating and addressing. Historic generally refers to buildings 50 years of age or greater with significance architecturally or culturally.
Thoughtfully and appropriately designed repair and restoration projects can preserve the integrity of the masonry building and continue its life for future decades. From a sustainability perspective, the greenest building is the one that already exists.
With greater knowledge of masonry material properties, wall systems, condition assessments, and best practices for repair and restoration strategies, design and construction professionals can successfully develop and implement appropriate solutions for their culturally significant and existing projects.
Put your restoration projects in the hands of qualified professionals.
Our intensive Historic Masonry Preservation Certification Program (HMPC) teaches the traditional craft skills and contemporary repair techniques required for sensitive restoration work.
We also offer project-specific training, like Terra Cotta Restoration and Replacement, Historic Lime Mortars, Guastavino Tile Vaults, and Concrete Repair.
Specify HMPC to be sure you have highly trained, qualified restoration professionals on your project, or contact us for project specific training opportunities.
It’s important to prioritize repairs based on the structure’s conditions and project team goals. Strategies differ per project and can be selected from a variety of repair options.
Photo: Eric J. Nordstrom
Mortar joints make up about 20% of the masonry facade and are important both aesthetically and functionally. Mortar joints are a vehicle that allow further breathability and vapor transmission of wall assemblies.
It’s critical that new pointing mortars developed for a project aren’t stronger, denser, and less water absorbent than the original mortar or masonry materials. Selecting an appropriate and compatible new pointing mortar is one of the most important decisions to make for facade repairs and restoration projects. Facades with early manufactured masonry materials, like soft and porous brick or a soft and porous stone type, have an even more critical need for appropriate mortar selection.
It’s also important to note that new materials are often different from historic materials. Cement and cementitious materials undergo higher kiln temperatures and are typically ground more finely, which can lead to stronger and denser mixtures. Be sure to select cementitious materials, which are appropriate and compatible with the masonry units and system you are repointing. This could include various types of lime, portland cement, natural cement, and pozzolans/alternative cementitious materials, or combinations thereof.
Many masonry repair and restoration projects have a cleaning component that coincides with repair work. Cleaning treatment should use the gentlest methods possible to achieve the desired level of clean without harming the surface of the masonry materials. Damage to the surfaces creates more porosity, which leads to subsequent premature damage and lowers the wall’s durability.
Cleaning options include water, chemical, micro-abrasion, and laser. Prior to selecting a treatment approach, it’s critical to understand both the type of soiling and substrate material properties. Cleaning options aren’t all the same, and they have specific properties with pros and cons for various conditions and materials. Not cleaning is also an option.
See IMI’s Masonry Restoration Cleaning Flowchart for a guided approach to cleaning both conventional and historic masonry.
In general, coating systems should not be applied to existing or historic masonry facade surfaces. Even the most breathable penetrating water repellent coating systems are known for trapping moisture, changing the vapor drive of the wall, and causing premature failure of the masonry facade. If there is a historic or existing coating system already applied, then a comprehensive assessment of the condition of the coating and how well it’s bonded is necessary. The type of existing coating also needs to be determined by testing so that the new coating system is compatible. Adhesion testing during mockups and the duration of work should be required.
Many existing masonry buildings, specifically mass or transitional wall types in cold climates, look to improve energy efficiency by adding insulation to the interior of exterior walls. Before making this decision, consider these things to avoid future damage and diminished durability.
Refer to ASTM E3069: Standard Guide for Evaluation and Rehabilitation of Mass Masonry Walls for Changes to Thermal and Moisture Properties of the Wall and our resources at the bottom of this page for additional information.
The fire resistance rating of an existing masonry wall can be established in 2 ways:
The IEBC’s Resource A – Guidelines of Fire Ratings of Archaic Materials and Assemblies provides tables of documented fire ratings of various assemblies used in the past, including masonry materials and elements. It doesn’t specify the levels of fire performance required for building components, since that’s controlled by the building’s occupancy and use as set forth in local building codes.
ACI 216.1/TMS 216 Fire Resistance Rating for Concrete and Masonry Walls contains design and analytical procedures for determining the fire resistance of concrete and masonry members and building assemblies. It uses the equivalent thickness method, where the solidity of a unit is determined and then compared to tables that provide an equivalent fire resistance for that thickness. Combinations of different materials, air spaces, and wall finishes are addressed in this standard.
CMU Backing
CMU Backing, Structural Steel Beam/Plate Lintel
Pressed Terra Cotta Units
CMU Backing, Fixed Lintel
Large Area (> 2 s.f. ±)
Small Area (1 s.f. ±)
Medium Area (2 s.f. ±)
Repointing Detail
Extruded TC Units
Pressed TC Units
Extruded TC Units
Pressed TC Units
Extruded TC Units
CMU Backing
Here are some commonly referenced standards and resources that you may find useful in developing appropriate repair and restoration strategies for your projects.
For material specific resources, check out our restoration material assembly pages.