Do You Need a Permit to Waterproof a Basement?

If you’re planning to waterproof your basement in Toronto or the GTA, you might be wondering: Do I need a permit? The answer depends on the type of work you’re doing. Some projects, like major foundation repairs or exterior excavation, usually require a permit, while smaller jobs, like sealing cracks or installing a sump pump, often do not. In this guide, we’ll walk you through when a permit is needed, when it isn’t, and how to go about applying – including what to know if your home is a heritage property.

When You DO Require A Permit

In Ontario – and specifically in Toronto or the GTA – there are several situations where basement waterproofing will require a building permit. Here are the most common:

1. Structural or Material Alterations

If you’re digging out or excavating around your foundation (for example, to install an exterior waterproofing membrane), that’s a structural change.
Lowering the basement floor or doing underpinning (strengthening or deepening the foundation) is another example; these typically require detailed engineering and building permit review.
Repairing or replacing foundation walls in a way that changes their structure also falls under this.

Regulatory Changes / Code Updates

Recently, as of 2025, the Ontario Building Code has added stricter rules around underpinning. For instance, underpinning now requires professionally engineered drawings (P.Eng), even for shallower digs.
Also, when doing excavation deeper than a certain threshold, or when your project affects the foundational structure, inspection and engineered design are more strictly enforced.

2. Drainage System Installation / Alteration

Installing a new interior drainage system (e.g., interior perimeter drainage channels).
Running new plumbing. In Toronto, a permit is required for installing a backwater valve.
Exterior drainage or weeping tile connected to the municipal storm/sewer network, depending on depth and connection.

3. Creating or Modifying Plumbing

Any significant plumbing work requires a building permit. The City of Toronto explicitly includes “install or modify plumbing systems” in its list of permit-required projects.
Adding or modifying a backwater valve also requires a permit.

4. Major Basement Alterations

If your waterproofing work is part of a larger renovation (e.g., finishing or restructuring your basement), and that work includes new walls, structural framing, or entrances. As per Toronto’s building-permit guidance, finishing a basement does require a permit when there are “structural or material alterations.”
Adding a second suite where waterproofing is involved may also trigger the need for a permit, especially when altering walls, plumbing, or access.

5. Work Involving Historical / Heritage Buildings

If your home is designated under the Ontario Heritage Act (Part IV or Part V), you may need both a building permit and a heritage permit before making alterations. (More on this in the next section.)

When You DON’T Require a Permit

Thankfully, not every waterproofing job demands a permit. Here are some scenarios where homeowners in Ontario, specifically within Toronto and the GTA, may not need one:

1. Minor Waterproofing Repairs

Sealing non-structural foundation cracks from inside the basement (e.g., crack injections) that don’t involve excavation is generally exempt.
Applying waterproofing coatings, membranes, or sealants to the interior surface, if you are not changing the structure or depth, doesn’t always trigger a permit. According to the Toronto Building Code, “waterproofing repairs to a basement” are listed among work that does not require a building permit.
Installing or replacing a sump pump, if not altering plumbing significantly, often does not require a building permit.

2. Finishing a Basement Without Major Alterations

If finishing (e.g., drywall, insulation) doesn’t include structural changes, plumbing, or creation of a new dwelling unit, a permit may not be needed.
Cosmetic or surface-level renovations that don’t touch the foundation or drainage may fall outside of permit requirements.

3. Routine Maintenance

Replacing non-structural waterproofing elements (like repointing masonry, small patch repairs) might not require a permit, but always check locally, because “routine” depends on your municipality.

What About Heritage Buildings? Do You Need a Separate Permit?

Yes! If your home is considered a heritage property, there are extra permissions to think about.

What Is a Heritage Building?

In Ontario, a property can be designated under the Ontario Heritage Act (OHA) in two main ways:

Part IV: Individually designated heritage properties.
Part V: Properties located within a Heritage Conservation District (HCD).

If your home is listed (on the City’s Heritage Register) but not designated, then usually a heritage permit is not needed.
But if your property is designated, you may need to get a heritage permit in addition to your building permit.

Why A Heritage Permit Is Required

The goal of heritage designation is to protect heritage attributes – architectural, structural, or decorative features that give a building its historical character. Altering or demolishing these features often requires formal approval.
According to the City of Toronto’s Heritage Permit Guide, any work that affects heritage attributes, especially externally visible changes, may need a permit.
Under the Toronto Municipal Code (Chapter 103), applications must be submitted for changes to buildings in heritage conservation districts (Part V) or individually designated properties (Part IV).

What Is Required For A Heritage Permit

If you need a heritage permit, here’s what the City typically asks for (at a minimum):

Detailed application form with property information and description of proposed work.
Photographs of existing conditions and heritage attributes (interior and exterior).
Location plan (site drawing) showing what will be changed.
Architectural drawings, including existing and proposed site plans, sections, and elevations.
Written specifications – materials, colours, how the work will be done, etc.
A detailed description of the property: age, construction, lot lines, heritage attributes.
A case for why you are doing the work, how it affects heritage features, and what steps you’ll take to mitigate the impact.
Technical heritage studies (depending on scope): condition assessments, heritage impact assessments, engineering reports, conservation plans, and construction management plans.

Why Do I Need to Apply for a Waterproofing Permit?

1. Safety & Structural Integrity

A permit ensures that the work meets Ontario Building Code standards. If your waterproofing includes excavation, underpinning, or structural repair, the city will review your plans to make sure they’re safe. This protects your foundation and your investment.

2. Compliance with Local Laws

Permitting ensures that all work is done legally. Skipping this step increases the risk of enforcement actions, stop-work orders, or fines.

3. Insurance Protection

Insurers may deny claims if the work was done without the required permits. If you waterproof without a permit and damage occurs later, you may be left entirely on the hook.

4. Resale Considerations

When you go to sell your home, unpermitted work can become a major red flag. Buyers or appraisers may demand proper documentation. Without it, you could face lower offers or need to retroactively legalize the work.

5. Quality Assurance

Permit applications often require professional drawings and engineering for more complex work. This means your waterproofing job is more likely to be done to a high standard. As DGI Waterproofing, we view permitting as part of delivering a reliable, long-lasting solution – not just as a bureaucratic step.

6. Access to Incentives

In some cases, there are rebates or subsidy programs that require a permit. For example, the City of Toronto offers a Basement Flooding Protection Subsidy of up to 80%, capped at $1,250, for installing a backwater valve – but only if a permit is obtained and the work is inspected.

Consequences of Not Getting the Appropriate Permits

Skipping the permit process can seem like a shortcut, but it comes with serious risks. Here’s what could go wrong:

1. Stop-Work Orders

If the city becomes aware of unpermitted work, inspectors can issue a stop-work order. That halts your project – sometimes for weeks – until the proper permits are obtained.

2. Fines and Penalties

Working without necessary permits can lead to fines or legal action. Building code violations or unauthorized changes may result in monetary penalties and forced demolition or rework.

3. Insurance Issues

As mentioned above, if something goes wrong (water damage, structural failure), your insurance provider may refuse to cover it if the work was not permitted.

4. Resale Problems

When you sell your house, unpermitted work is a literal red flag for buyers and inspectors. It can complicate or scuttle a sale, or force you to retrofit and legalize work after the fact, which is often more expensive than doing it right the first time.

5. Structural Risks

Without proper engineering or inspections, structural changes (like underpinning or excavation) might not meet code. That can jeopardize the long-term safety of your foundation.

6. Heritage Violations

If your property is heritage-designated, doing work without a heritage permit could violate local bylaws, harming your property’s heritage fabric – and potentially triggering enforcement or fines under heritage conservation rules.

How to Apply for Waterproofing Permits: Step by Step

Here is a clear, homeowner-friendly breakdown of how to apply for permits for basement waterproofing in Ontario, especially around the GTA – from start to finish.

1. Initial Assessment

Talk to a licensed, experienced waterproofing contractor, ideally, one familiar with local codes. (That’s what we do at DGI Waterproofing.)
Have a waterproofing contractor or an engineer assess your basement: Is excavation needed? Structural change? Drainage overhaul?
Determine whether your home is heritage-designated (you can check the City of Toronto Heritage Register).

2. Hire a Professional (If Needed)

For complex work (underpinning, excavation), hire a Professional Engineer (P.Eng). As of 2025, underpinning in Toronto must be engineered.
Engineer provides stamped drawings—foundation plans, structural details, drainage, etc.

3. Prepare Application Documents

Complete the building permit application via your local municipality’s building department (online or at the permit counter).
Submit engineered drawings, site plan, cross-sections, waterproofing method, and materials.
If heritage: Prepare the heritage permit application (if required) with photos, architectural plans, context, heritage-impact study, and description of materials/changes.

4. Pre-Consultation (Optional, but Helpful)

Meeting with city staff or heritage planners may help clarify what documents are needed.
Use this meeting to ask about timelines, neighbour notification (if excavation), and any special local restrictions.

5. Submit the Permits

Submit your building permit application.
If your property is heritage-designated, submit your heritage-permit application concurrently (often reviewed in parallel).
Make sure everything is complete – missing or unclear documents are a common reason for your application being rejected or delayed.

6. Review and Approval

The building department and/or heritage planners will review. This may take a few weeks to months, depending on complexity.
For heritage permits (Part IV), a decision is legally due within 90 days of a “complete” application, unless extended.
If issues are raised, you may need amendments or additional documentation.

7. Pre-Construction Steps

Once approved, obtain your permit documentation. Post permits are visible on site, as required.
For excavation: You may need to call Ontario One Call to locate utility lines, arrange shoring, and provide neighbour notification in writing.
Confirm insurance, contractor liability, and engineer oversight.

8. Construction + Inspections

As DGI Waterproofing performs the work, the building inspector may visit at key milestones (excavation, structural reinforcement, drainage, backfill) to verify compliance.
Keep photographic records, as well as engineer sign-offs or daily logs if required.

9. Final Inspection & Permit Close-Out

After work is complete, request a final inspection from the city.
If everything is compliant, the inspector will sign off, and your permit is officially closed.
Keep permits and inspection documentation – you’ll need them for resale, insurance, or warranty claims.

Call DGI For Assistance With Waterproofing Permits

At DGI Waterproofing, we believe in doing things right. That means high-quality workmanship and full legal compliance. Waterproofing your basement isn’t just about keeping water out – it’s about safeguarding your home’s structure, its value, and your peace of mind.

If you’re thinking about waterproofing your basement in Toronto or anywhere in the GTA, reach out. We can assess your situation, help determine whether you need a permit (or a heritage permit), guide you through the application process, and execute the work in full compliance with Ontario’s building code.

Let us help you protect your home – from the ground up.