A cracked and bowing basement wall is no longer structurally sound. Once cracked, it is far easier for hydrostatic pressure to continue to push the wall inward. This article will address the various methods used to stabilize a concrete block basement wall to prevent further inward movement due to hydrostatic pressure. Our method of choice is Fortress Kevlar/carbon fiber straps. We have over 2 decades of carbon fiber installation experience. Our owners introduced carbon fiber to the Cleveland market first. Over the years we’ve installed every brand of carbon fiber on the market. Here’s some helpful information regarding this fantastic product:
Carbon fiber is exceptionally strong. When the strands of carbon are woven or placed parallel with each other, they become exponentially stronger than many other materials. Carbon fiber, when bonded to a bare or properly prepared concrete surface, will not delaminate or stretch. Fortress carbon fiber, with a cross weave of Kevlar, has been tested to be 10 times stronger than steel in a tension application, meaning being pushed, not compressed. When tested to failure, Fortress carbon fiber endured a force ten times what is necessary to stabilize a basement wall as shown in this video of the actual testing. The installation is non-invasive, 99.9% dust free, and the structural epoxy adhesive contains no VOCs (volatile organic compounds). You don’t need to leave the house!
Carbon fiber composites are as high-tech as you can get today. The new 787 Dreamliner aircraft, space shuttles, boat masts, racing bicycles, racing cars, bullet-proof vests are all made from this modern day miracle composite. Carbon fiber has been used for many years for repairs to concrete bridges and commercial and industrial concrete structures. Fortress carbon fiber products now routinely replace steel I-beams, wall anchors, and Grip-Tite anchors for most cement-block basement wall repairs. The advantage of carbon fiber over these older technologies is well documented, tested and proven.
Before we compare the various methods of stabilizing a basement wall we need to clarify that we are talking about concrete block basement walls. We also need to verify that the cracks are due to the wall being pushed inward and not due to settling. Inward movement generally results in a horizontal crack along the entire wall with stairstep cracking at the corners and sometimes stairstep cracks on the adjacent walls. Vertical cracking from floor to ceiling, especially on two adjacent walls, is usually settlement; the foundation is sinking in some areas. None of the following stabilization methods are designed to address foundation settlement. Proper failure analysis is critical for any successful long-term repair. Note that spacing requirements of the methods described below will vary depending on block thickness, wall height, backfill height, and the amount and type of wall damage.
Traditional wall stabilization almost always involved the installation of steel beams. These beams were often bolted to the floor or set into the floor and cemented in place. They were then attached at the top of the wall and to the floor joists with framing. Not all size steel beams are strong enough to withstand hydrostatic soil pressure loads. Sometimes undersized beams are installed to save the contractor money. Steel beams are bulky and can be scary to future potential purchasers of your home. That doesn’t mean there is never an application for using them. We do install steel beams in some situations. Expect to pay $650-750.00 per beam.
Rod & Grout
Rod & grout stabilization was the next method to come along. Steel rebar is inserted into the wall and then cemented into place along the length of the rods. There are many skill and knowledge factors required for this work that many installers are unaware of. The rods must be tied into the sill plate and extend below the floor. The grout has to be a specific mix. Rod positioning along the entire wall length is crucial. Merely sticking rebar in the wall and pumping in concrete does little for structural integrity if guidelines are not followed or understood. This process adds thousands of pounds of weight to your footing. We install a rod & grout repair when necessary, most often for the shearing at the very bottom of the wall. Cost is $50 – $100 per location.
Steel Wall Anchors
Steel wall anchors are a steel rod which passes through your block wall and is anchored into the soil outside. The hole in your wall is then patched, and a 20″ steel plate is bolted to the rod on the inside of your basement wall, then tightened with a torque wrench. These anchors require manual tightening every month to maintain the warranty. Wall anchors are suggested for solid poured concrete walls, but not block walls. You cannot drywall or cover these wall plates as they need to be continually accessed to maintain their function and your warranty. We carry them. They cost $550 – $750.00 each.
Full Wall Anchors
Full wall anchors do the same thing as the anchors above but have a 6′ wall plate mounted on the wall with a nut which requires monthly tightening. Again, you can’t finish the walls since you need access to tighten the anchor bolts monthly. The appearance of these anchors is almost as daunting as steel beams. We decided not to carry these. They cost $550- $750.00 each.
Carbon fiber is the latest entry into the residential wall stabilization race. Carbon fiber has been tried, tested and proven to have a tension strength 10 times stronger than steel beams. Carbon fiber is available in 3 main forms: 1) fiber mesh patches 2) solid plate and 3) carbon fiber straps.
Carbon fiber mesh patches are only 2′ – 4′ generally installed midway up the wall. Often these patches do not address the higher hydrostatic pressures developed at the bottom two blocks of the wall because they are not long enough. These patches also usually do not cover the top several horizontal rows of block, which are subject to frost breakage and movement. Spacing seems to vary depending on the vendor. Long-term adhesion to the wall has been a problem in the Cleveland, Ohio area with some companies. We carry fiber mesh patches as this repair is warranted in specific scenarios. Price varies with patch sizes.
Carbon fiber solid plate is manufactured to withstand standard hydrostatic pressure but not differential movement and pressure as it is manufactured with the carbon strands aligned in one direction only. This product requires cleaning with methyl ethyl ketone before installation. This extra heavy design often doesn’t conform well to the bow and displacement of a bowed wall because it is so thick. It is also difficult to confirm 100% wall adhesion because you can’t see if all the air voids have been removed after it is installed. We carry this but it is generally used for heavy-duty commercial projects. Each plate costs $650 – $850.
Carbon fiber straps are the most versatile of all the carbon products. Fortress Kevlar/carbon fiber straps are designed to address differential pressure movement as well as standard hydrostatic pressure. High strength structural adhesive epoxy bonds it to the wall and passes through its woven grid pattern to surround and encapsulate the entire strap. Any trapped air or voids can easily be visually identified and removed. You can expect to pay $550 – $750 per strap which includes top and bottom anchoring.