We use 1/8th inch Galvanized Cable in all our curbing. This will help keep the curb together at the control joints and at any cracks that may occur. Curbing is a concrete product and if a curbing company says their curbing never cracks they are simply not telling the truth. We have very minimal cracks as we use the correct ratios and techniques when it comes to mixing concrete and finishing. Spider cracks can occur in concrete and must not be mixed up with separation. You must remember that cracks can and will occur in concrete. Many factors contribute to this including materials, layouts, and temps. The main issues with landscape curbing are extreme angles, inclines, and declines. You must realize that a curbing machine weighs approx. 210 lbs. so getting enough compression is extremely difficult in these situations. Cracks are concrete issues, they can and will happen. Cracks that are over 1/4 wide on level ground are an issue with operator error or lack of compaction, these cracks will be covered under warranty. Cracks in all other situations are not. We put the control joints closer to relieve stress, but cracks can occur, they are a fact of concrete life. We are dealing with moving concrete.