You may be in the mood to beautify the external appearance of your property and are thinking about applying some decorative concrete treatments to external walls. However, on closer inspection, you can see that cracks have appeared in the host surface. Should you just go ahead and apply the decorative treatment in this situation, in effect just covering it up? What do you need to consider first?
Static or Moving?
Firstly, you need to have a much closer look at any cracks and determine whether they're likely to get worse or not. Most hairline cracks are essentially "static" and won't develop into anything much greater than they already are. They can be caused by shrinkage or one-time events and are just, essentially, a fact of life. Usually, you can just leave them and apply your decorative treatments on top, without worrying anymore.
However, if you can determine that the crack is deeper or ongoing, this is what's known as a "moving" crack, and it is essentially structural. These will look more substantial by their very nature, but one trick is to try to cut down into the crack and see how far it goes. If it only goes so far and then stops, it's likely to be a static crack.
How Should You Proceed?
You definitely need to conduct some repairs before doing any decorative overlay to a moving crack. Otherwise, it will continue to grow beneath and could cause a complete delamination of the decoration that you put on top.
How to Effect a Repair
You will need some specific repair tools and materials in order to fix a moving crack. You have to smooth and then widen the edges with a specific saw so that the crack is completely cleaned out. Then, you'll probably have to apply a primer before putting the repair material inside.
There are a number of different types of products available for this situation, ranging from caulk that you can manipulate with your fingers to tough acrylic that is very difficult to penetrate. They fall into three different categories—flexible, semi-rigid or rigid.
In most cases when you are placing a decorative application on top, you should choose a semi-rigid epoxy. This type of material will permit a small amount of movement in the crack, but not enough to affect what you're putting on top. In some situations, you may be able to put a special layer of fibreglass into the mix, protecting it even further.
Bringing in the Experts
If you're unsure about the extent of your problem, it is best for you to bring in specialists in concrete crack repairs.