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Carbon Fiber has been used since the early 1800’s (Thomas Edison and the light bulb filament). But it really began gaining traction in the 1960-1980 time period when carbon fiber polymers were used in cars, planes and structures. At the turn of the century – carbon fiber was being used for structural reinforcement and repairs. In foundation repair we first began hearing about carbon fiber back in the mid 2000s.
Foundation Worx installs carbon fiber reinforcement for two major structural repair and foundation repair issues.
Carbon fiber repair (for residential applications) primarily comes in two forms
We are trained and certified to install the Stronghold brand carbon fiber reinforcing materials.
Some frequently asked questions of this product are covered here:
Q. Can I trust that StrongHold carbon fiber systems offer the same reliability as steel systems?
A. If properly designed, the answer is overwhelmingly yes! Over 20 years of Large-Scale Testing for applications that include repair and strengthening of concrete, masonry, steel, and wood structures support StrongHold carbon fiber systems. In each of these tests, carbon fiber was shown to out-perform steel alternative repairs. The StrongHold products never corrode like steel and offer greater tensile strengths without the obstructions or adversely effecting the aesthetics of your basement wall. The StrongHold products have also been installed in major commercial, industrial, and civil applications since the mid 1990’s with no failures. In fact, StrongHold’s parent company, HJ3 Composite Technologies, has repaired over 2,000 structures worldwide and sold over 2,000,000 square feet of carbon fiber for those repairs. Our carbon fiber systems are approved by the Department of Defense for blast protection, Mine Safety Health Administration for underground blast reinforcement for mine seals, Metropolitan Water District Los Angeles, CA for lining underground high-pressure water pipe, and various cities and county water, wastewater, and numerous state departments of transportation.
Q. How does the price of the StrongHold Bowing Wall kits stack up against competitors’ products?
A. Even though the StrongHold product offers superior testing, engineering, and strength when compared to the competition it is priced very competitively with those repair systems. Yet, what often isn’t considered when comparing the price of the StrongHold kits is that our kits include a primer coat (critical to adhesion) and all of the consumables and installation equipment necessary to install the StrongHold system. The competitors’ pricing only includes the carbon fiber and the associated resins. The extra cost to secure the tools required to do the installation cause StrongHold to be substantially less expensive.
Q. After reviewing StrongHold’s competitors’ products I noticed that they do not use a primer coat prior to installing their carbon fiber reinforcement. Is it important to use a Primer Coat prior to installation of the StrongHold Bowing Wall system?
A. The answer is absolutely. The primer coat is an extremely low-viscosity epoxy that penetrates deep into the pours of your concrete or masonry wall. This creates a stronger, deeper interlock in your wall that greatly improves adhesion of the layer of carbon fiber. By using the StrongHold primer, bond strength to the substrate is increased, allowing for proper load transfer of the external soil pressure through the wall to the carbon fiber straps. None of StrongHold’s competitors utilize a primer in their carbon fiber systems and have experienced failure through de-lamination.
Q. Why is StrongHold carbon bowing wall systems spaced between 3-foot on center to 5-foot on center while other bowing wall systems offered by your competitors are always spaced 4-foot on center?
A. Some competitors, not all, incorrectly space their reinforcing systems based on the American Concrete Institute’s (ACI) 530 design guideline which states that “the maximum spacing for steel external reinforcement is four times the thickness of the masonry wall, or generally 4-feet”. ACI 530, however, is specific to original masonry wall design and makes no mention of plastic external reinforcement for repairs (carbon fiber systems are considered a plastic). As engineers we are responsible for using the state of the art design guide available to guide our repairs. All designs for your basement therefore should be based on the latest “state of the art” design guide published by the American Concrete Institute, ACI440.2R (2008) “Strengthening of Concrete with externally bonded FRP composites”. ACI440.2R, unlike ACI 530, differentiates between the performances of steel reinforcement compared to the performance of plastics by considering reduction factors for sustained loading (the continued force of the soil pressure on your basement wall) on the carbon system. When companies’ properly follow ACI440, the varying parameters for basements (height of wall, height of backfill, thickness of wall, type of soil) will translate to specific loads (pounds per inch per width) and the specific spacing of carbon reinforcement required to resist those loads. I think we can all agree that steel behaves differently than plastic and that each basement application is different.
Q. Why does StrongHold offer both semi rigid carbon plates and flexible carbon fabrics for bowing wall repairs?
A. As your wall reacts to the force created by external soil pressure, it begins to bow. The bowing action in your wall, and subsequent displacement, makes it difficult for the semi-rigid plates to conform to such curvature. In these instances it is typically ideal to use the bowing wall fabric. The 10-inch wide flexible carbon fabric can develop the same strength (pound per inch per width of material) as that of the 4-inch semi-rigid carbon plate. These products are therefore interchangeable relative to strength, the decision on which to use should be based on constructability and aesthetic requirements.
Q. Why do some competitors offer carbon fabrics for bowing wall repair that are 24-inches wide, while StrongHold’s carbon fabric is only 10-inches wide?
A. The width of the reinforcing system required to resist external soil loads is contingent on the amount of tensile strength (measured in pound per inch per width) yielded by the carbon fiber reinforced system (fabric plus resin). HJ3’s patented carbon reinforcing fabrics used for bowing wall repairs offer up to 2.5 times more tensile strength than competitors’ products. Thus, competitors are forced to offer wider systems, up to 24-inches, to yield the tensile strength required to resist external soil pressures. The advantage of the 10-inch wide fabric is (1) improved aesthetics (as less wall space is covered with the reinforcing system) without having to pay more money for the StrongHold system; (2) wider systems also require significantly more surface preparation, well over double the effort when compared to the StrongHold alternative.
Q. Why do some competitors offering carbon fabrics only repair 5 feet along the height of wall, while StrongHold extends their carbon bowing wall system along the entire height of the wall – usually 7 to 8 feet?
A. StrongHold engineers recognize that no soil behaves the same way when exposed to different conditions. Distribution of external soil forces will not always concentrate in the mid-span of your basement wall. In some applications the concentration of forces may be in the upper 1/3 or bottom 1/3 of your wall. By extending the repair along the entire height, StrongHold engineers account for all three scenarios, which ensures the most reliable strengthening system. If you cover only a portion of the wall – especially masonry walls – the path of least resistance for soil or hydrostatic pressure will be the areas not reinforced by the competition.
Q. Up to what deflection is carbon fiber an acceptable strengthening system?
A. 2-inches is a good rule of thumb for most applications. To determine deflection in your wall, it is important to measure the difference at the greatest deflection (usually at the mid-span of the wall) as compared to the original plane of the wall.
Q. What repair options do I have if my wall is deflected beyond 2-inches?
A. Several options are available and offered by many StrongHold trained installers. The first option is to excavate out the soil that is pressing against your wall. Once the soil pressure is released the wall will gain back some or all of its deflection, bringing it below the 2-inch deflection limit. The StrongHold bowing wall carbon fabrics or laminates can then be installed at their proper spacing. At this point, the installer will back-fill the excavated soil with sand and aggregate in place of your original soil to decrease the force that will build against your basement wall going forward. A second option is to use steel mechanical systems such as steel tie-backs. The steel tie-backs tend to be considerably more expensive than the StrongHold Carbon Systems but may be required to remove the deflection from the wall without excavation.
Q. If my wall is deflected less than 1/2-inch, should I still purchase StrongHold to strengthen my basement wall?
A. The deflection in your wall is a sign that the external soil pressures are greater than the load your wall can support. Over time, the deflection will most likely worsen. As your wall continues to deflect, crack patterns will form, allowing pathways for water to leak into your basement and for mold to form. By utilizing StrongHold carbon fiber systems at the first sign of deflection you can prevent the issues from becoming any worse. Strengthening achieved with StrongHold will brace the wall, allowing crack injection resins and waterproofing measures to stay in place to stop leaks and moisture penetrations.
Q. My wall is deflecting (turning) inward at the top and doesn’t seem to have much of a “bow”, can I still use the StrongHold Bowing Wall Kit?
A. No. If the top of your wall is moving inward then there is most likely a different, more serious structural deficiency, which no Fiber reinforcement system can stabilize. StrongHold systems work by developing the “internal” compressive strength within the wall to resist lateral loads. If the top or bottom of the wall is moving, known as “kickout” or “turning”, then the issue is considered to be an “external” failure. It is highly recommended this kind of failure be reviewed by a licensed civil or structural engineer.
Q. Do I need to attach the StrongHold carbon material to the ceiling joists and the floor?
A. No. Within a typical masonry or concrete wall there is a huge amount of strength which is undeveloped due to internal structural failures. By using the StrongHold Bowing Wall Carbon System, you are utilizing the strength already built into your wall instead of relying on your wood ceiling to resist the soil and water pressures. By tying composite reinforcement to wood, our competition is only transferring the force to another structural member, compensating for a reinforcement material which is weaker and has lower bond strength.
Q. Can the StrongHold Bowing Wall Repairs be used to fix settlement or sagging walls?
A. No matter what anyone tells you the answer, at this time, is NO! If any contractor tells you that the carbon fiber can resist settlement make sure to contact StrongHold and discuss solutions with one of our on-staff structural engineers. Settlement in a home is a serious structural issue that must be evaluated by a structural engineer (PE/SE) licensed in your state. While there has been research completed on the use of carbon fiber for resisting settlement forces, it is still in research and development and is not an accepted repair procedure. As StrongHold completes testing and research on these issues we will publish the results here on our website.
Q. Is there anything I can do to prevent further water damage or water build up on my basement walls?
A. The main culprit in 90% of foundation and basement problems is water. It saturates the soil against your wall adding pressure and decreasing the soil’s ability to hold itself up (generating lateral force against the wall). The best advice we can give is to limit your home’s exposure to water, by: (1) installing gutters to allow the drainage system to guide runoff away from home; (2) cleaning gutters every fall to assure gutters can drain the water away from the home; (3) bring in extra fill material to create a “positive grade” away from your home (often times dirt slopes toward wall, causing water to pool up and soak in); (4) avoid having plants or trees near the wall, water from irrigation systems routinely cause problems especially if there are unknown leaks in plumbing. Roots also can press against the wall or grow into tiny surface cracks, making them expand; (5) while not water related, homeowners should limit surface loads (installing a new driveway, building, patio, or other structures) next to the wall to avoid extra lateral pressures.