Flooding in Southern Ontario: Understanding and Preventing Basement Flooding 

On August 17, 2024, Toronto and surrounding areas were hit by heavy rains, leading to sudden flooding in several neighborhoods. This dramatic event reminds us of the importance of protecting our homes, especially basements, against the risks of flooding. How do these floods occur in basements, and what can you do to prevent them? 

How Does Water Enter a Basement? 

Basements are particularly vulnerable to water infiltration for several reasons: 

1.      Hydrostatic Pressure and Foundation Cracks: When the soil around the house becomes saturated with water, hydrostatic pressure increases. This pressure forces water into the basement through foundation cracks, masonry joints, or even through concrete walls. 

2. Water Seepage Through the Slab: A poorly sealed or damaged concrete slab can allow groundwater to seep into the basement. This is often exacerbated by a high water table. 
3. Infiltration Through Basement Windows: Poorly sealed or low-set basement windows can easily let water in, especially if they are surrounded by poorly drained window wells. 
4. Drainage System Failure: A clogged or poorly designed French drain cannot effectively divert water away from the foundations, leading to water backing up into the basement. 
5. Gutter Downspouts and Discharge Lines: A gutter downspout or discharge line that releases water too close to the house can cause flooding, especially if the discharged water is in large quantities. 
6. Power Outage: Although most homes have a sump pump to direct water to the discharge line, a power outage can render the pump useless, increasing the risk of basement flooding. 

How to Prevent Basement Flooding? 

There are several solutions to protect your basement from flooding: 

1.      Install a Sump Pump System with a Backup Pump: A sump pump is essential for evacuating water that accumulates around the house. In a flood-prone area, it is recommended to invest in a sump pump with battery backup to ensure its operation even during a power outage. Sump pump systems that include multiple pumps and a backup pump, such as the SuperSump and TripleSafe systems, are available. 

2. Seal Walls and Floors: Applying waterproof membranes to interior and exterior walls, as well as sealing the slab, can help prevent water infiltration. 
3. Maintain the Drainage System: It is essential to regularly check that the drainage system is functioning properly. A clogged drain can quickly become a major problem. Additionally, an interior drainage system like WaterGuard has proven to be efficient and effective. It might be worth considering investing in an interior drainage system, which can be installed more quickly than an exterior French drain since it doesn't require excavation work. 
4. Install Flood-Resistant Basement Windows: Modern flood-resistant windows are better sealed and equipped with well-drained window wells, reducing the risk of water infiltration. 

While we hope not to experience similar circumstances to those of August 17th, it is crucial to take proactive measures to protect our basements. By understanding the potential causes of flooding and investing in the right solutions, you can protect your home from costly damage.