Adding a basement to your property or deepening an existing crawlspace is one of the most valuable upgrades homeowners in Kingston, Napanee, and Frontenac County can invest in. A basement significantly increases usable living space and property value while making your home more flexible for rental units or multi-generational needs. In many neighbourhoods, particularly older ones in central Kingston, the only way to meaningfully expand your home’s square footage is to dig a basement.
But how much does it cost to dig a basement in 2025? The answer depends on a wide range of local variables. Site access, foundation type, soil conditions, drainage, waterproofing systems, and building permits all play a role. Whether you’re planning to dig a basement under a heritage home or during a new build, knowing what to expect can help you avoid budget surprises and delays.
At M. Riddle Excavating, we have helped dozens of clients successfully dig a basement across Eastern Ontario. Our hands-on knowledge of the terrain, municipal requirements, and engineering challenges makes us a trusted excavation partner for complex basement excavation projects.
Why Soil Conditions Matter When You Dig a Basement
The soil beneath your property is the foundation of any excavation plan. In Kingston, you may encounter anything from soft sandy loam to dense clay or limestone bedrock. These variations affect the time, equipment, and techniques needed to dig a basement safely and effectively.
Hard soils or shallow rock formations often require more powerful machines, specialized operators, and even hydraulic breakers. Soft or sandy soils may seem easier to dig, but they pose stability issues that require engineered shoring to prevent collapse during excavation. Every time we dig a basement, we begin with a soil assessment, often in partnership with structural engineers and surveyors.
The cost to dig a basement in favourable soil can start around $10 to $20 per square foot. In difficult conditions, particularly where limestone is involved, the price may exceed $40 per square foot. For more information on regional soils, homeowners can consult the Ontario soil survey database, which highlights constraints for excavation and construction in rural and urban zones.
Costs to Dig a Basement in 2025
In general, homeowners can expect very different cost ranges depending on whether they plan to dig a basement under an existing house or as part of new construction. For new builds, excavation typically costs between $12,000 and $36,000, depending on size and soil complexity. This assumes you are starting with a clear lot and have full equipment access.
Digging a basement beneath an existing home is a more involved and costly process. This requires underpinning or benching to preserve the home’s structural integrity while removing material from beneath it. In 2025, the average cost to dig a basement under an existing home using underpinning falls between $300 and $500 per square foot. That includes shoring, excavation, concrete work, structural inspections, and multiple permits. Benching, a less invasive method, comes in at $200 to $300 per square foot but limits usable floor space and ceiling height.
Whether you are trying to gain a legal rental suite or simply want more finished space, the decision to dig a basement needs to be guided by both structural feasibility and local code requirements.
Waterproofing and Drainage for Below-Grade Spaces
Every time we dig a basement, our team also addresses the risks of water infiltration. Waterproofing is not just a finishing step – it should be designed into the excavation plan from day one. Without adequate drainage systems and protective membranes, a new basement can quickly become vulnerable to leaks, humidity, or even flooding.
In 2025, full exterior waterproofing with membrane application, drainage boards, and perimeter weeping tile typically ranges from $5,000 to $10,000. The cost can be lower for smaller foundations or where existing systems can be modified. Interior waterproofing, including sump pumps and sealant coatings, is also common, though less durable for high water table areas like Glenburnie or Kingston’s Inner Harbour district.
At M. Riddle Excavating, we often dig a basement while simultaneously installing or upgrading waterproofing and grading. This integrated approach prevents duplicated effort and gives our clients the best protection against long-term water damage. Learn more about the combination of services that can be accomplished by viewing recent projects and case studies.
Permits and Municipal Coordination
Before you dig a basement, you’ll need to secure the proper permits. Excavation and structural modifications must follow the Ontario Building Code, and in most cases, detailed drawings by a licensed engineer are required. Permit fees vary by municipality but usually fall between $500 and $2,000 for excavation and underpinning work.
If your property includes a private septic system, you’ll also need to review the system’s capacity and location before proceeding. Adding a basement often involves relocating tanks or expanding leaching beds. Our team offers full septic system design and installation for clients planning to dig a basement on rural properties. We work directly with public health inspectors and planners to avoid delays.
We also support our clients by handling inspection scheduling and submission of engineering documentation.If you’re unsure what permits you’ll need for your property, reach out to our team with your list of questions for free advice from local experts.
What to Expect When You Dig a Basement in Kingston
When clients ask us how long it takes to dig a basement, we explain that timelines vary based on site access, foundation type, and weather. A straightforward dig during new construction can be completed in under two weeks. Excavating beneath an existing structure typically takes four to six weeks, including underpinning and inspection phases.
Delays often result from missing documentation, poor drainage planning, or unexpected soil challenges. That’s why we always recommend beginning with a full site evaluation before you dig a basement. This early investment helps reduce changes mid-project and avoids costly redesigns.
Clients who dig a basement with M. Riddle Excavating also benefit from our ability to coordinate directly with other trades. We frequently work alongside builders, architects, and engineers to streamline communication and reduce downtime on-site. Whether the project includes full finishing or stops at the foundation stage, we provide accurate cost forecasting and schedule tracking throughout.
Final Considerations
Deciding to dig a basement is one of the most significant construction choices a homeowner can make. It offers tremendous benefits in terms of space, value, and future-proofing, but it also requires deep planning, sound engineering, and precise execution.
In Kingston, the cost to dig a basement can start around $50,000 for existing homes and around $12,000 for new construction foundations. Factors like soil conditions, underpinning methods, drainage requirements, and permit costs will all influence your final investment. As excavation professionals who live and work in the region, we take pride in helping our clients understand these costs and make informed decisions.
To explore your options and get a realistic quote to dig a basement on your property, contact our team. You can also browse our Projects for recent examples of successful basement digs in and around Kingston.