How Excavation and Shoring Can Affect Nearby Properties in Ontario
Excavation is a normal part of many construction projects in Ontario, from new residential developments to commercial buildings and underground parking structures. But when excavation takes place close to an existing building, property, road, or other structure, it can create additional risks that need to be considered before construction begins.
Removing large amounts of soil changes the conditions around the excavation. Depending on the depth of the excavation, soil type, groundwater, and distance from nearby structures, surrounding ground can move or settle. This is one reason why proper planning, shoring, and accurate surveying are important on construction sites.
Why Can Excavation Affect Nearby Properties?
When soil is removed from a site, the ground around the excavation can respond to the change in pressure and support. If the excavation is close to an existing building, even relatively small ground movement can potentially affect foundations, walls, sidewalks, or other nearby structures.
The level of risk depends on several factors, including:
- Depth and size of the excavation
- Type and condition of the surrounding soil
- Distance between the excavation and nearby buildings
- Groundwater conditions
- Type of shoring system being used
- Construction methods and sequencing
- Existing condition of neighbouring structures
This does not mean that every excavation project will cause damage. With proper engineering, construction planning, and site control, many of these risks can be managed effectively.
What Is Shoring?
Shoring is a temporary support system used to stabilize the sides of an excavation during construction. It helps prevent the surrounding soil from moving into the excavation and provides protection for workers, structures, and nearby infrastructure.
The appropriate shoring method depends on the project and site conditions. Common systems may include soldier piles and lagging, sheet piles, secant piles, or other engineered support systems.
For projects in Toronto and the GTA, shoring is especially important when construction takes place in a built-up area where neighbouring buildings and infrastructure are located close to the property line.
Surveying can also play an important role during shoring installation. Accurate layout helps contractors locate piles and other construction elements according to the engineered design.
How Ground Movement Can Affect a Building
One of the main concerns with excavation near an existing property is ground movement.
If surrounding soil moves or settles, a nearby building may experience changes in its foundation or structure. The effects can range from minor cosmetic cracks to more significant movement, depending on the site and the amount of displacement.
Some signs that may appear include:
- New cracks in walls or masonry
- Cracks around windows and doors
- Doors or windows becoming difficult to open
- Changes in floor elevations
- Cracked sidewalks or driveways
- Movement of retaining walls
It is important to remember that cracks do not automatically mean excavation caused the problem. Older buildings may already have existing cracks or settlement. This is why documenting existing conditions before construction can be very useful.
Why Baseline Measurements Matter
Before excavation begins, project teams may establish survey control and collect measurements of important areas around the site.
These measurements create a baseline that can be used for comparison later.
For example, if a building corner has a particular elevation before excavation, that measurement can be compared with future measurements. If a change is detected, the project team has objective data showing what has changed and when.
This can be much more useful than relying only on visual observations.
For projects where ground or structural movement is a concern, ongoing survey measurements can help identify changes during construction. AKM Surveying provides monitoring services that can be used to measure changes such as settlement and displacement during construction projects.
Which Projects May Need Extra Attention?
Not every construction project requires the same level of survey control or monitoring. However, additional care is often appropriate when excavation is deep or located close to existing structures.
Examples include:
- Deep basement excavations
- High-rise construction
- Underground parking projects
- Excavation near older buildings
- Construction close to property lines
- Projects involving extensive shoring
- Excavation near roads and sidewalks
- Projects close to underground infrastructure
In these situations, understanding the existing site conditions and establishing reliable survey control can help the construction team make better decisions.
The Role of Surveying in Excavation Projects
Surveying on a construction site is about more than property boundaries.
A surveyor can help establish accurate control points, set out construction elements, check elevations, and provide measurements that contractors and engineers can use throughout the project.
Depending on the project, survey work may include:
- Shoring pile layout
- Construction control points
- Foundation layout
- Elevation checks
- Site grading
- Monitoring of selected points
- Construction verification
- As-built surveys
Having accurate survey information can help reduce mistakes and keep different members of the construction team working from the same reference system.
For larger excavation projects, survey data can also provide useful information when the project team needs to investigate unexpected movement or changes on site.
How Can Construction Teams Reduce Risk?
Good preparation is one of the best ways to reduce problems during excavation.
Before construction starts, the project team should understand the existing conditions around the property. Nearby buildings, utilities, roads, sidewalks, retaining structures, and other features should be considered during planning.
It is also important to establish reliable survey control and document relevant existing conditions.
During construction, the team should follow the engineered shoring design and pay attention to any unexpected changes. Where appropriate, regular measurements can help identify movement early.
The exact approach will depend on the project. Engineers, contractors, surveyors, and other specialists may all have different responsibilities, but accurate site information helps everyone work with a clearer understanding of what is happening.
Planning an Excavation or Shoring Project in Ontario?
Excavation near an existing building requires more than simply removing soil. The surrounding environment, neighbouring properties, and existing structures all need to be considered.
Accurate surveying can provide valuable information before and during construction, whether you need shoring layout, construction control, elevation checks, or monitoring of selected points.
AKM Surveying works with contractors, developers, engineers, and construction teams across Toronto and the GTA to provide professional surveying services for a wide range of construction projects.
Planning an excavation, shoring, or construction project? Contact AKM Surveying to discuss your project and request a quote.