Frequently Asked Questions
Only Fortress has ICC-ES approval, making it the only carbon fiber system that meets building code guidelines. This is very important. Whatever you do, make sure your system is building code compliant. Ask to see their ICC-ES report. Our ICC-ES Report is on this site as well as the ICC website. We would be glad to email you a copy as well. Our Report title is ESR-3815. This link will take you to the official ICC web site.
Prior to Fortress grid strap, there were two types of carbon fiber commercially available: wet layup (tow sheet), and protruded plate. Both of these have pros and cons. After evaluating the strength and weaknesses of available products, Fortress developed the Carbon Fiber/Kevlar grid strap.
Wet layup: Must use more fabric for wall coverage to achieve desired strength and must be impregnated on the job site, which is messy. This also requires a much higher skill level in getting tows straight. Any misalignment of tows and carbon has no strength at all. If used on damp walls it may also fail to properly bond.
Protruded Plate: Very strong; however, it is also very rigid and typically has very poor bonding capabilities. Epoxies do not bond well to epoxies or polyester resins. This can be a disadvantage on deflected surfaces. It depends on a “sandwich” bond as well, where voids can be typical and unseen.
Fortress Stabilization Systems Carbon Fiber Kevlar Grid Straps has the advantages of both the wet lay up and protruded plate but eliminates the disadvantages related to both.
The National Association of Home Builders (NAHB) has prepared their own guidelines to help resolve issues that arise in all types and kinds of construction, not just foundation walls. It is the Residential Construction Performance Guidelines (RCPG) 4th edition. This guideline says under, Basement and Crawl Space Concrete Block Walls, sections: “Observation” A concrete block basement wall is out of plumb “Performance Guideline” Block concrete wall shall not be out of plumb greater than 1″ in 8 ft when measured from the base to the top of wall. This is what contractors use as guidelines when building foundation walls, provided that there is a contract signed by the owner and contractor agreeing to the guidelines. A true plumbed wall foundation that is built out of plumb to the 1″ in 8 ft can stay that way for the life of the building, provided that there are no unusually high lateral forces action on it or cracking. Unusually high lateral forces can cause cracking and bowing even on a perfect aligned wall.
The simple answer is no, and most ways of straightening walls require excavation. Tie-backs may, over a period of time, straighten walls to a certain degree. Tie-backs tend to creep or loosen and may punch through and twist a masonry wall when tightened. So the required tightening of tie-backs every 6 months is adjusting the grip that can loosen. The lamination of carbon fiber will hold the wall in it’s current deflection or can be applied after straightening to hold the wall in place and strengthen the foundation.
In compliance with code A.C.I. 530, the maximum spacing for external reinforcement is four times the thickness of the masonry wall. Straps are placed up to 4-ft apart according to the requirement. This is with a 2.5 safety factor.
At the time of carbon fiber lamination, tuck pointing all cracks will assure a wedge when the wall attempts to hinge. Tuck pointing material goes into compression not allowing the wall to move outward; the laminated carbon fiber will not allow the wall to move inward. Contractors should be able to diagnose and address this issue upon install.
Strengthening of a Structure Composite Design Guide ACI 440-F states:
A Class-A FRP system can be used as long as it is self-extinguishing. A Class-B can be made a Class-A by utilizing ¼ gypsum board or coatings.
Fire ratings can be misleading. Fire ratings are a timetable calculating the time a person has to leave a burning building. A Class-A fire rating is a measure of how much smoke is produced and how quickly the resin burns.
Painted on fire coatings such as in tumescent paints help by swelling and insulating the surface below. The reaction time of a coating and heat deflection of epoxy is far different. For example: heat deflection of Fortress 4020 is 175 degrees and foaming of coatings is around 300 degrees. Most epoxies are self-extinguishing after the fire source is removed.
FRP is a Reinforced Polymer or plastic. The kind of fibers used play little role in its performance in a fire. The fibers maintain their physical properties at high temperatures; they are actually produced at extreme temperature. Carbon Fibers are manufactured by cooking at roughly 1,900 degrees F.
It therefore is the bonding agent that is in question under fire. The most common bonding agent is a thermo set plastic, two-part resin: such as epoxies, vinyl esters and polyesters. It is Glass Transition Temperature Tg. where polymer begins to soften and how resin performs. Thermo-sets do not re-harden and lose any physical characteristics of hardened laminate.
Tg is a function of initial cure temperature. For example: many per preg plates and grids are cooked over 300 degrees. Therefore their glass transition is at or higher than 300 degrees. Epoxy resins in the field are usually cured at room temperature and have a Tg of roughly 120 to 175 degrees.
In conclusion the difference between 120 degrees Tg and 300 degrees Tg is simply the amount of time. Yet you will have a Class-A fire rating. A thermal barrier such as ¼ gypsum board will improve this. However, like many of the compounds that make up a building, depending on the duration of heat and smoke, multiple components may be lost and in need of replacement.
Yes! We recommend sanding lightly in order to help the paint stick. Just enough to scuff the surface. DO NOT use solvents. Any type of paint may be used to cover the straps.