Bisson Expert has completed more than 1,800 foundation repairs on the Plateau Mont-Royal, half of which were projects aimed at stabilizing foundations, granting us the well-earned reputation of a company with high-level expertise in this part of Montreal. Here is a typical example of foundation settling on the Plateau Mont-Royal due to soil with poor load-bearing capacity or dried out clay.

Last September, a foundation expert from Bisson Expert inspected a triplex with carriage entrance built in the 1900s that showed multiple signs of settling. Occurring frequently in this nice Montreal neighbourhood, land subsidence is a major problem for owners. Even more so when it is a heritage building that has a quarry stone foundation. Fortunately, there is a permanent solution set forth by our foundation experts: stabilizing the building on steel piles. Read this article and find out more about this project.

What caused the land subsidence ?

Like many other areas in the metropolitan area, the Plateau Mont-Royal is known for land subsidence problems. When this happens, the buildings look like they are settling because they are literally sinking into the ground. This is when cracks appear, wide crevices form in the bricks and interior walls and doors don’t close anymore, etc. These land subsidence warning signs were very visible in this triplex.

Our experts identified three factors that led to this problem :

• A soil with low bearing capacity

Foundation problems often appear where the ground is clay, such as on the Plateau-Mont-Royal in Montreal. Indeed, during periods of drought such as we experienced in the summer of 2016, the lack of water dramatically dries up the land. Under these conditions, clay soil shrinks, loosens from the foundation and creates a void around it. This is what happened here: the soil dried up, resulting in the foundation sagging.

To learn more about soil subsidence in times of drought, see our article on this topic

• Urban development
Here, in the Plateau Mont-Royal district, dry soil conditions have intensified due to urban development. It is a common phenomenon in cities. Because the land has been excavated to install sewers, gas systems, etc., the rain can no longer drain naturally. Consequently, very little water seeps into the clay soil, which in turn accelerates land subsidence and foundation settling.

• Quarry stone foundation
Like many buildings in the Plateau Mont-Royal district, this triplex is equipped with a quarry stone foundation.

This is an old construction method that was used in the 1900s. Today, foundations are made of concrete, but back then, foundations were built with stones that were stacked and the holes were filled with mortar. This construction method has its own set of problems when the mortar crumbles over the years. Furthermore, the materials used for the building façade were very heavy. This weight combined with the soil conditions contributes to the settling of the foundation and therefore, the building. This is what happened here.

How did we solve the problem of land subsidence on this property?

Like all other land subsidence problems, the permanent solution is to stabilize the foundation on steel piles sunk into the bedrock, i.e. about 20 feet deep. To understand how we proceed in such cases.

Diagnosis by our engineer

First of all, a Bisson Expert engineer went to the Plateau to evaluate the situation and recommend the best solution and a detailed plan. It is extremely important that this step be carried out by an expert, because work on a quarry stone foundation is more complex than on a concrete foundation. Prior to installing the piles, the quarry stone foundation must be inspected to ensure that it will hold up and not crumble.

The building stabilization required 46 steel piles sunk into the bedrock using patented hydraulic equipment to ensure uniform pile driving without any vibrations or damages to the building.

A load test was then performed. During the test, an expert technician checked the stability of the piles and applied twice the prescribed load on each pile.

To find out more about the steel pile installation process, see our detailed article on this subject.

Given that the quarry stone foundation was set directly on the ground, our experts had to build up the foundation by adding a concrete tie beam at the base. This step was needed to support the base of the quarry stone foundation and to homogenize it with the piles supporting the building.

For a permanent solution to land subsidence, choose an expert !

To put an end to land subsidence and foundation settling, stabilizing the foundation on steel piles is the durable solution. However, because this is such a complex procedure where even the smallest detail counts, be sure to choose a skilled expert before commencing work. Also, bear in mind that Bisson Expert has been in operations since 1955 and has acquired all the expertise and skills needed to offer you quality workmanship. Do as our Plateau Mont-Royal client, who owns several triplexes and has given us our 5th mandate, and trust our integrity !

For more information on this subject, click here.

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