When dealing with basement leaks associated with concrete block foundations, waterproofing must not be considered in isolation. If there is any evidence of concrete block / cinderblock movement, structural stabilization or reinforcement should receive serious consideration. The most typical symptoms of structural issues associated with block walls are visible horizontal cracking (usually visible only from inside the basement) and step cracking in the mortar joints.
In the picture above, the horizontal cracking in the mortar joint immediately below the top course of blocks is plainly visible. This horizontal cracking typically occurs at grade (the height of the soil outside) and results from the force of soil pressure applied to the foundation. This tends to occur as a foundation ages because the mortar joints weaken from the cyclical pressure applied against the foundation by the expanding and contracting soil outside.
Because changing soil pressure on a weakened concrete block foundation wall can ultimately lead to structural failure over the course of many years, relatively simple reinforcement systems have been developed to arrest foundation movement exemplified by horizontal cracking, step cracking and bowing of the block wall towards the interior of the basement. One such reinforcement system involves the use of carbon fibre reinforcing straps. The following illustration shows the typical installation of the carbon fibre reinforcing straps used to stabilize a concrete block / cinderblock wall.
For more details on the concrete block wall reinforcement system that we recommend and install, click on the brochure picture below.
The next image is a completed perimeter drain installation system that included the installation of carbon fibre reinforcing straps. The installed reinforcing straps will prevent the foundation wall from moving inwards when pressure is applied against the wall by the soil outside.
The first step involved in the installation of a carbon fibre reinforcing strap is grinding of the wall surface onto which the reinforcing strap will be installed. This wall grinding is done to ensure excellent adhesion of the subsequently applied epoxy to the wall, as well as to ensure that the foundation wall surface is as flat as possible.
Wall grinding will generate a tremendous amount of dust; therefore it is crucial that the waterproofing contractor use a negative air machine or air scrubber to minimize the amount of dust within the work area, and the home in general.
The image below clearly shows the ground area of the block foundation wall onto which the carbon fiber reinforcing strap will be installed.
After grinding the wall, the dust is brushed off the wall and epoxy is applied onto the wall surface. The area over which the epoxy will be applied corresponds to the width and length of the carbon fiber strap that will be installed.
The epoxy on the wall is then spread evenly over the wall surface.
Below is an image showing the prepared substrate onto which the reinforcing strap will be installed. Carbon fiber reinforcing straps are typically 6.5' long.
The reinforcing strap (also referred to as a carbon fiber/Kevlar™ grid system) is unique in that it is currently the only pre-cured product that is fully encapsulated in epoxy.
By encapsulating the carbon Kevlar™ grid in epoxy, every hole in the grid allows the epoxy applied to the surface of the grid to come into contact with the epoxy previously applied to the wall; as a result, epoxy rivets are formed. These rivets act as rip stops which prevent the grid (or reinforcing strap) from peeling off the foundation wall. The image below shows a fully epoxy encapsulated reinforcing strap.
In the image below you can see 3 installed carbon Kevlar™ reinforcing straps at the recommended spacing of 4' apart. Once the epoxy has fully cured, the cracked or moving foundation will be permanently repaired as the wall is now 3 times stronger than it was originally.
