Protecting performance without compromising integrity
Historic buildings present a unique challenge. While their materials and construction methods were designed for longevity, many were not built to withstand the environmental conditions and performance expectations placed on buildings today.
Water intrusion is one of the most common and damaging issues affecting aging structures. Over time, exposure to moisture can lead to material deterioration, structural damage, and loss of architectural detail. Waterproofing plays a critical role in preserving these buildings, but it must be approached with a clear understanding of both performance requirements and historic integrity.
How water impacts historic construction
Unlike modern assemblies, historic buildings were often designed to manage water through mass and permeability rather than complete exclusion. Materials such as brick, stone, and lime-based mortars allow moisture to enter and exit the assembly, relying on drying cycles to maintain balance.
When this balance is disrupted, problems begin to develop. Trapped moisture can lead to freeze-thaw damage, cracking, efflorescence, and corrosion of embedded metals. In some cases, previous repairs or incompatible materials can exacerbate these conditions by limiting the building’s ability to dry.
Understanding how water moves through these assemblies is essential to selecting the right waterproofing approach.
The role of waterproofing in restoration
Waterproofing in historic buildings is not about creating a fully sealed enclosure. Instead, it is about controlling water entry, directing drainage, and supporting the building’s ability to manage moisture over time.
This often involves a combination of strategies:
- Below-grade waterproofing to prevent water intrusion at foundations and basement walls
- Traffic coatings and plaza deck systems to protect occupied spaces below exposed surfaces
- Sealants and joint systems that accommodate movement while maintaining water resistance
- Drainage improvements to reduce hydrostatic pressure and manage runoff
Each of these elements must be selected and detailed in a way that aligns with the existing structure and materials.
Material compatibility and system selection
One of the most important considerations in historic preservation is compatibility. Modern waterproofing materials can offer high performance, but not all are appropriate for use with historic substrates.
For example, vapor-impermeable coatings applied to masonry can trap moisture within the wall assembly, accelerating deterioration rather than preventing it. Similarly, rigid materials used in areas subject to movement can lead to cracking and failure over time.
Selecting the right system requires an understanding of how new materials will interact with existing conditions, including permeability, movement, and exposure.
Coordination at critical details
As with most building envelope systems, failures in historic structures often occur at transitions and details.
Common areas of concern include:
- Roof-to-wall intersections
- Parapets and coping conditions
- Window and door perimeters
- Below-grade transitions and foundation interfaces
These locations are often more vulnerable due to age, prior modifications, or material degradation. Proper detailing and coordination across trades are critical to ensuring continuity and performance.
Balancing preservation and performance
Waterproofing historic buildings requires balancing two priorities: protecting the structure and preserving its character.
Interventions must be carefully planned to minimize impact on original materials and architectural features, while still addressing performance requirements. This often involves working within existing constraints, sequencing work to limit disruption, and selecting systems that can be integrated without altering the building’s appearance.
A performance-driven approach
At TWC Phoenix, waterproofing for historic structures is approached as part of a broader building envelope strategy. This includes evaluating existing conditions, identifying moisture pathways, and coordinating solutions that align with both preservation goals and long-term performance.
By focusing on system compatibility, detailing, and execution, the goal is to extend the service life of historic buildings while maintaining their structural integrity and architectural value.
Closing perspective
Historic buildings were not designed for today’s environmental conditions, but with the right approach, they can continue to perform for decades to come.
Waterproofing plays a central role in that process. When properly designed and executed, it helps manage moisture, prevent deterioration, and support the long-term preservation of the structure.
For guidance on waterproofing strategies in historic buildings, contact TWC Phoenix to discuss your project and building envelope requirements.