Core fill is an alternative method contractors use when installing basement waterproofing and repairing a bowing wall conflict. The preferred way to fix a bowing wall is through installing carbon fiber straps. However, installing straps in the traditional way will ruin an interior water drainage system. Core fill resolves this conflict.
Started by Andy Beery in 1996, Acculevel is a home repair company that specializes in waterproofing and foundation repair. So far, we’ve helped over 30,000 homeowners preserve and protect their homes, and we strive to treat every home as if it were our own. This means we are mindful of taking any actions that will negatively affect your home or violate the warranty on an existing home repair.
In this article, we’re going to explore the typical methods for basement waterproofing and for installing carbon fiber straps. We’ll discuss how these two services collide, and how core fill allows them to coexist.
A Brief Review of Water Drainage Installation
If you are interested in a more detailed review of all the water drainage types that Acculevel offers, this article breaks down each type and the circumstances when we use it. For this blog, we’re going to use water tunnel as our example.
This illustration was done by the author, who is not a graphic designer.
In the illustration above, you can see a small orange circle that represents the best placement for water tunnel drainage. To install this, the basement floor is broken up next to the wall. The drainage is installed directly on top of the footer, and a new floor poured over the top of the waterproofing tunnel.
How It Works
Water trying to get into the basement will first permeate through the wall. It will run down inside the wall, then pool up in the bottom concrete block. Eventually, when the block is full, the water leaks into the basement.
When Acculevel installs water drainage, we drill weep holes in the bottom block. Any water that makes its way into the wall runs down and out through the weep holes directly into the water tunnel. The water tunnel collects the water and sends it to the sump pump, where the water is pushed out of the home through a discharge line.
With me so far? If you have more questions about basement waterproofing, please use our Homeowner’s Guide to Basement Waterproofing. This guide answers all of the FAQs we receive from customers, and provides detailed information about the products and methods we use.
A Brief Review of Carbon Fiber Straps
For a detailed look at carbon fiber straps, this article explains why it’s the best method to repair a badly cracked or slightly bowing basement wall. For this particular discussion, we’re going to jump straight to the more technical discussion.
The number one priority when Acculevel is repairing a bowing wall is stabilization. We want to be sure that the wall is securely held in place, so that it will resist the pressure to bow further.
How They Work
The carbon fiber straps Acculevel installs are made of kevlar-grade carbon, and are permanently adhered to the wall using a special type of epoxy. They are anchored at the top and the bottom of the wall by specially designed brackets.
This illustration is taken from Fortress Stabilization Systems, who manufacturers our carbon fiber straps.
The above photo shows the anchors in detail; the top is secured to your home’s sill plate. The bottom anchor is attached to the base of the wall- which requires us to break up the concrete floor right next to the foundation wall.
This bottom anchor needs to be attached to the bottom of the wall, to prevent shearing. Shearing is the term used to describe how a wall sometimes breaks. The concrete block on the bottom is held in place by the basement floor. But if there’s enough hydrostatic pressure pushing on the wall, it can separate from the bottom row of blocks and slide inward.
This illustration was done by the author, who is still not a graphic designer.
How Do These Two Repairs Conflict?
If you have water tunnel drainage installed under the basement floor, it’s flush against the wall- in the exact same place the bottom anchor needs to be for the carbon fiber strap.
We obviously want to secure the carbon fiber strap, to make the repair permanent. But if we drill through the drainage to attach the bottom anchor, the anchor will compromise or block the drainage- which nullifies the warranty on the water drainage.
So, that presents the question: how do we prevent shearing without using the bottom anchors?
Core Fill is the Answer
The solution to this dilemma is to secure the lower rows of concrete blocks as one piece. The blocks have hollow cores (centers), so we can join them together on the inside of the wall. We drill a hole through a block several rows up, insert a piece of steel rebar, then fill the core with concrete.
By cementing the bottom rows together, the strap no longer needs to be anchored to the base of the wall; the “base” of the wall is now several rows deep. And because the core fill goes into the block, it goes behind the water drainage instead of through it.
This photo was taken by an Acculevel crew member after installing an epoxy fill to the cracks, carbon fiber straps to stabilize the wall, and core fill to replace the bottom anchor.
Do You Need More Information about Foundation Repairs?
Throughout this article, we’ve linked to resources that further explain the various services and products. If you have additional questions or would like more details, please check out our Foundation Guide for Homeowners.
Please bookmark this guide and refer to it whenever you have questions about your home’s condition, symptoms that develop, or indications that you may need to make repairs.
If You Need Waterproofing or Foundation Repairs
If you don’t live in our service area, make sure you work with an insured and reputable local company that is accredited by the Better Business Bureau. We have a checklist of questions you should ask a contractor, with a free downloadable form. Compiled with input from our project managers, management, and crews, these questions will help you determine if the contractor(s) you meet will be the best fit for you and your home.