When the Ground Shakes: How Boston’s MBTA Green Line Extension Construction is Impacting Historic Masonry Buildings

The completion of Boston’s MBTA Green Line Extension in 2022 marked a significant milestone for public transportation in the Greater Boston area. However, the massive construction project, which cost $2.3 billion and spanned several years, has left an unexpected legacy for property owners throughout Somerville and Medford: widespread concerns about construction-induced vibrations and their impact on historic masonry structures.

Understanding Construction Vibration Damage to Masonry

Construction vibrations from major transit projects like the Green Line Extension pose unique risks to Boston’s historic masonry buildings. The minimum vibration level to damage older homes with plaster-on-lath construction is 0.50 in/sec, while masonry and concrete building components are particularly rigid and vulnerable to vibration damage. The densely populated areas surrounding the Green Line Extension route contain numerous historic brick and stone buildings that were never designed to withstand the prolonged vibrations generated by modern construction equipment.

The $2 billion Green Line Extension Project traversed one of the most densely populated cities in the United States, which made construction noise and vibration an important factor for the Project. The construction process involved installation of deep foundations using concrete, steel, and timber piles driven into the ground with large hammers or vibratory methods, both of which generate large vibrations that can damage adjacent properties.

How Vibrations Affect Different Types of Masonry

Not all masonry structures respond to vibrations in the same way. Wood and steel are more elastic than masonry, such as brick and stone. At lower frequencies, walls tend to deform more, subjecting the brittle materials from which they are made (such as brick and mortar) to higher stresses and strains. This makes historic Boston masonry particularly vulnerable to the types of vibrations generated during major construction projects.

The first signs of vibration-related damage appear on the interior planes of vertical loadbearing walls, as these walls resist the lateral swaying and movement caused by vibrations. Damage to rigid finishes first appears as cracks at the weakest locations in the wall, which is generally at the corners of window and door openings.

Common types of vibration-induced masonry damage include:

• Hairline cracks in the mortar joints of brick or concrete block constructions
• Formation of significant cracks or loosening and falling of plaster surfaces, as well as cracks through bricks or concrete blocks
• Major damage affecting structural elements, including cracks in support columns, loosening of joints, and splaying of masonry cracks
• Cracking of foundation walls and excessive sloping of floors

The Green Line Extension’s Ongoing Challenges

The Green Line Extension has faced numerous construction-related issues that have extended the timeline and increased vibration exposure for nearby buildings. Roughly 50 percent of the Union Square branch and 80 percent of the Medford/Tufts branch need to be “regauged” to increase the space between the two rails, with MBTA officials aware of track problems as early as 2021, or 11 months before the first portion of the expansion opened to riders.

These ongoing construction issues mean that property owners in the affected areas continue to experience vibration-related impacts even after the initial project completion. The need for extensive track repairs has resulted in additional construction activities that generate more vibrations, potentially causing cumulative damage to masonry structures that may have already been weakened by the initial construction phase.

Professional Masonry Assessment and Repair

When construction vibrations affect masonry structures, professional assessment becomes crucial. Academy Masonry, a trusted masonry company in Boston, Middlesex County, and Suffolk County, focuses on creating long-lasting relationships through honest communication, transparency, and a commitment to exceeding expectations on every job. With over 25 years of dedicated service, Academy Masonry is a family-owned and operated business serving Boston, specializing in masonry and construction, committed to delivering 100% customer satisfaction.

For property owners concerned about vibration damage from the Green Line Extension construction, masonry boston specialists can provide comprehensive evaluations to determine whether observed damage is related to construction activities or pre-existing conditions. Academy Masonry prides itself on using high-quality materials and advanced techniques to ensure the durability and beauty of masonry work, whether clients need expert chimney repair, retaining wall installation, or paver installation.

Protecting Your Property

When construction work occurs nearby, the nature of the construction work, its location, the type of machinery used, and the duration of machinery use provide important information for investigation. Pre-construction survey reports sometimes make it possible to identify damage that was already present before the work began.

Property owners should document any new cracks, settling, or other structural changes that occur during or after major construction projects. Areas where damage typically shows up from ground movement include chimney connections, corners of openings, and spots where rigid and flexible materials meet. Binding doors and windows can also hint at recent structural movement.

The Path Forward

While the Green Line Extension represents a significant improvement to Boston’s public transportation infrastructure, its construction impact on historic masonry buildings cannot be ignored. Academy Masonry values quality, durability, and aesthetics, understanding that homes and businesses are significant investments. Their expertly installed masonry work not only augments the appearance of properties but also adds long-term value.

For property owners in areas affected by the Green Line Extension construction, professional masonry evaluation and repair services are essential for maintaining structural integrity and property value. Early detection and proper repair of vibration-induced damage can prevent more serious structural problems and costly repairs in the future.

As Boston continues to invest in infrastructure improvements, understanding and addressing the impact of construction vibrations on historic masonry buildings remains crucial for preserving the city’s architectural heritage while advancing its transportation goals.