The reason you should paint the cinder blocks is that it will help preserve the wood posts. By painting the blocks, you are waterproofing them.
If they aren’t painted, they are absorbing water, so the wood will be sitting in holes that are constantly wet when it rains.
Even though the posts will be stained and coated with urethane, they will be much more likely to rot. Painted cinder blocks will dry much more quickly and wick away much of the water.
How to Make a Cinder Block Bench Step by Step Tutorial
Step 1. Wash The Cinder Blocks
Place the cinder blocks on top of something so that they aren’t sitting on the ground. That way they don’t end up sitting in their own dirt and can dry more quickly.
I had square cinder blocks leftover from another project that I used to raise them.
Add TSP to the soap canister in the power washer, or fill a 2 gallon bucket with water and ¼ cup of TSP and wash down the blocks, if hand washing, use the scrub brush to help remove dirt and oil.
Let these dry in the sun at least a day, and flip them at least once. The blocks must be completely dry before you paint them or the paint will peel.
It may take more than a day to dry, especially if it’s not sunny. Wind will help.
You may notice in the photo that there are also concrete blocks, if you missed it in the intro above, those are for the upcoming planter box add-ons.
Step 2. Prime And Paint The Blocks
Spray a coat of primer onto the blocks. Make sure to thoroughly coat the cinder blocks so the pores are filled, also don’t forget to get inside the holes.
Check the manufacturer’s label on recoat times, but you should be able to flip the blocks after an hour and your time to recoat is probably going to be approximately 4 hours under ideal conditions.
If after 4 hours, the blocks feel dry and are not tacky, then go ahead and apply the first coat of paint.
Alternatively, if you don’t have a paint sprayer, use a paint brush to prime and paint the blocks.
If you are using the same acrylic exterior paint as I have recommended in the materials list, then your time to recoat is approximately 4 hours.
So if the paint feels dry and isn’t tacky after 4 hours, you can apply your second coat of paint. You may need three coats.
If you see any lighter spots still coming through, then go ahead and apply a third.
Step 3. Sand And Stain The 4x4s
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