Tree roots: What you need to know

Last updated March 30, 2023
Reading time: 2 min

Trees play an important role in the fight against climate change, which is why Montréal is planting so many. Some people mistakenly believe that tree roots can damage such things as building foundations, pipes and sidewalks. So what’s the true story?

Montréal has committed to planting 500,000 trees by the end of the decade to combat and adapt to global warming and to improve the population’s well-being and quality of life. Trees have many benefits. They produce shade and oxygen, capture some of the carbon dioxide (CO2) responsible for global warming, and make the air more breathable.

Can tree roots damage the foundation of a building, pierce pipes, or damage a staircase or sidewalk?

How the roots grow

The way roots grow does not exert pressure on the wall of a house or building. The tips bypass obstacles by slowly flowing around and binding to them. Root growth occurs in two stages: the first stage in which tissues composed of gelatinous material develop, and the second stage in which these same tissues harden and become wood.


If a foundation already has cracks large enough to allow air and water (two essential elements for root growth) to pass through, they will gradually be colonized by roots and neighbouring plants. If left unchecked, this phenomenon can worsen the condition of the building structure. Although the roots are not responsible for the damage, they prevent these cracks from closing.

Pipes and sewer lines

Waste accumulation, wear and tear over time and freeze-thaw cycles are responsible for the cracks. Roots only enter damaged or leaking pipes and conduits.


Sidewalks can be damaged by the wear and tear of time, weather action, freeze/thaw cycles, the passage of heavy machinery (such as during snow removal) or because of poor construction. As they crack, sidewalks lose their strength. This allows the roots to grow into the cracks and occupy the space left open by the shifting of the sidewalk. The growth and development of the tree is therefore not the cause.

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