Installing an undermount sink in a concrete countertop is similar to installing it into other countertops with a few small but important differences. The process can be long, but patience will yield some satisfying results.
Step 1: Preparation
To begin, always remember to put on your work gloves and safety goggles for safety purposes. Wearing a mask is a good idea so that you do not accidentally inhale any dust or debris. It would be a wise idea to cover any surrounding areas with plastic or tarps to protect them, as well.
Step 2: Cutting the Counter Top
Cutting a solid surface, especially one like concrete, is not a job for most people. If you are uncertain about it, it is best to leave that part to a professional. If you are, however, familiar with these processes, you need to start by taking measurements of the sink. Once you have those, you can use the diamond-bladed saw to cut the concrete to the specifications that you need.
If you're worried about gaps between counter and sink, cut your hole ½ to ¾ inch shorter than what your measurements specify. It's easier to go back and make the hole bigger if necessary than it is to make it smaller if you cut too big.
Step 3: Polishing and Cleaning
Use the diamond polishing pads to polish the rough edges until it is smooth. When you are done with this, it is very important to clean the area. Failure to thoroughly clean this can result in your adhesive not sticking very well.
Step 4: Holding Up the Sink
The most difficult part of installing an undermount sink can be trying to hold it up while you're installing it. To make this simpler and easier on you, place a 2x4 board across the countertop. Then place one end of the bar clamps upon the board, while using the other through the sink drain hole to hold it up. This is a crucial part of the process; you'll want to make sure that the sink is flush against the bottom of the counter top.
Step 5: Apply the Metal Clips
When dealing with concrete, you're going to need to use an epoxy adhesive to make the metal clips that hold up your sink stick. Apply the epoxy where your specifications require the clips to be and then place the clips over it. You will need to wait at least a day for the epoxy to fully dry.
Step 6: Caulking
Use your silicone caulking to go over the underside of the sink where it meets the counter top. This will prevent any leakage from occurring where the sink meets the bottom of the counter.
Step 7: Finishing Up
It's now time to reattach plumbing. When you're done with this, your sink will be ready for use!