Control joints are planned for cracks which allow for movements caused by temperature changes and drying shrinkage. In other words, if the concrete does crack, you want to have an active role in deciding where it will crack and that it will crack in a straight line instead of randomly.

We space joints properly. We space joints no more than 25-40 times the slab thickness. A 100mm slab should have joints 2.5-4.0m apart.

We cut joints 30% of the depth of the slab. A 100mm thick slab should have Expansion Cuts at least 30mm deep.

We cut expansion joints as soon as the concrete is hard enough that the edges abutting the cut don't chip from the saw blade.

In hot weather, concrete might crack if joints are not cut within 6-12 hours after finishing concrete. In this condition a Soff Cut saw can be used almost immediately after finishing the freshly laid concrete. However Soff Cut sawing cannot successfully be done on coloured concrete as marks will be left from the cutting blade skidplate.

When we cut house floors we place joints under walls or under carpet areas. Under walls they won't be seen.

Note: Inside corners, where cracks would typically occur, have correctly placed joints.

Top Class Concrete has all the right gear and knowledge to get it right, and leave you with the piece of mind of knowing your concrete has been prepared, laid and maintained by trained professionals.

Questions

Some questions we have been asked about this service.

WHY DOES CONCRETE CRACK? As concrete dries it shrinks and when it shrinks, cracks appear. We expansion cut concrete to help determine where the crack is going to appear so that when it does crack, it is concealed by the expansion cut. Please note that at times, cracks may appear in random areas where expansion cuts have not been placed.

HOW CAN I STOP MY CONCRETE FROM CRACKING? Before starting your new project, you must plan ahead. It is crucial that you choose an experienced concrete placer as they will know the correct techniques needed to reduce the risk of your concrete cracking. Along with having an experienced placer, it is important that concrete be expansion cut. All cuts must be in the correct place, be the correct depth and be cut at the correct time, so when the concrete does shrink, correctly placed cuts will guide the cracks to where the cuts are. Having said this, even when all the necessary precautions are taken unfortunately, on occasion, concrete may still crack in random places.

HOW FAR APART SHOULD MY DECORATIVE CUTS BE? This depends on the size of your concrete area and personal preference. Many people ask for their concrete to be cut into 1 metre squares, however this is not always possible so we adjust the size to ensure the design fits into the designated area.