We recently started a new series on our blog called Construction 101, where we explain some of our most commonly used construction terms. Last month we explained what “excavation” is and this time around we’re going to look at “shoring” which is one of the most important steps in the early construction stage.
Shoring is the process used to retain the wall surrounding the site to ensure that the earth material doesn’t erode (cave in) and fall into the excavation. Shoring is extremely important because it protects the surrounding and neighbouring property and keeps them in-tact and undisturbed.
Shoring is put in during the excavation process bit by bit until it is done all the way down to the bottom of the foundation. The shoring stays in forever. It is never removed as it would be impossible to access it once the building is constructed.The shoring is only needed until the structure is built at which time the structure holds the earth as well. The shoring also has “TieBacks” which are steel cables that are drilled horizontally into the adjacent property to support the vertical piles from moving inward.
There are two different methods to complete shoring on a site. Both methods involve drilling a hole from the top all the way down to the bottom of the future excavation hole at which time steel piles (or I beams) are lowered into the hole that has been drilled with the massive drill bit. Once the piles are in the hole, it’s then filled with low strength concrete (so that it can be scraped flat later once the hole is dug.) The first method of shoring is building a caisson wall. In between the piles more holes are drilled and the entire cavity is filled with the concrete. The second method of shoring is using a lagging” system. For lagging, as the machine digs down – wood beams are wedged from one pile to another to act as the in-fill pieces.
Here at Minto we use both types of shoring. At Minto 30 Roe for example, we use both caisson wall and the lagging system. We use the caisson wall when there is very little space between the neighbouring properties and when drilling will leave too little material behind to act as the support system. We used the lagging system at Minto 30 Roe on the South and East sides of the property, which don’t have an existing structure on the neighbouring property (the North nd West do so they are caisson wall). When there is nothing structural in close proximity at risk during the excavating, we are able to do lagging rather than caisson wall. This is because there are not any neighbouring foundation/footings etc in danger as we excavate!
Thanks to Jason Waters our Site Superintendent at Minto for all the information! We’ll have another Construction 101 post soon!