There are several reasons why basements leak, the most common reasons are:

• No gutters/downspouts
• Improper grading
• Defects in the foundation (a defect or crack in your foundation doesn’t necessarily mean that your basement will leak)
• Heavy rain
• Freeze/Thaw (this is happening quite a bit this year in the Ottawa area)
• Improper/missing/damaged exterior flashing/caulking
• Improper/missing chimney flashing/cap
• Hydrostatic pressure

As homeowners, we need to understand how moisture affects the building envelope and understand the effects of moisture intrusion.

No Gutters/Downspouts

Gutters and Downspouts are one of the most important and cost-effective way to control water. Our rooves are designed to shed water (like your umbrella), we use gutters and downspouts to send that water away from the building – the recommend distance from your foundation is 1.89m (6 feet).

Gutters have the following 2 functions:

• They protect the exterior cladding of a building from water that would ordinarily run off the roof, this water can damage the wall surfaces and cause localized erosion at the ground.
• The second and the most important is that gutters and downspouts will help to ensure a dry basement.

The less water/moisture in the soil near the foundation, lowers the risk of water penetration. Also remember, concrete functions just like a sponge.

Common problems with gutters/downspouts

Leakage is the most common, gutters will leak for various reasons; these are the most common:

• Galvanized steel gutters will leak due to perforating rust.
• Copper gutters will also leak due to perforating rust.
• All gutters are prone to leaking at joints and seams.
• Gutters are clogged
• Gutters have improper slope
• There aren’t enough downspouts (There should be a downspout every 10.668m [38’] to 12.192m [40’].

This leakage can cause damage to the fascia/soffits/walls below and contribute to basement leaking.

Lot grading

It’s a pretty simple theory, if there is no water in the soil beside your foundation wall, water won’t wick into your basement. Many wet basement problems can be eliminated or dramatically reduced with proper lot grading and gutters/downspouts that are performing well. 

Defects in your foundation

If you have a crack in your foundation, it doesn’t mean that it will leak. Horizontal cracks in your foundation require a foundation specialist to shore it. Vertical cracks, although uncomfortable to look at may not be detrimental. 

Signs to look out for:

• Water stains around cracks
• Efflorescence
• Standing water

If you have evidence of this in your basement, I recommend an inspection of your gutter system and lot slope. Many cracks can be repaired with out a costly exterior excavation, and many issues can be avoided with proper drainage away from your home.

Heavy Rain and Freeze/Thaw cycle

During periods of heavy rain, it’s difficult to control the saturation levels of the soil near your home. All materials used in home construction has what’s called a hygric capacity. Once the hygric capacity of the soil is reached, the moisture will find new materials to hydrate. In this case, your foundation, and because of thermodynamics; hydrodynamics and the laws of fluids – water will find its way into your basement. 

With a freeze/thaw cycle, like we’ve been seeing this year in Ottawa, it is not uncommon to see basements that don’t normally leak, leak.

When these events occur (precipitation) proper remediation should be executed.

Improper flashing/caulking

Flashing and caulking are what we use to help protect the interior construction material. It, like your roof is designed to shed water away from your home. These need to be inspected yearly, especially exterior caulking. Caulking has a relatively short life span compared to other components used to protect your home from moisture intrusion.

Hydrostatic pressure

Hydrostatic pressure is what forces water into your basement. It is the pressure exerted by a fluid (in this case water) that has reached an equilibrium at a given point within the fluid, this is due to the force of gravity. Hydrostatic pressure increases the deeper we go.