Posted on Jul 19, 2020
I wanted to build a pergola in my backyard. The patio is a cement slab. I could fasten post bases to it for the posts but I felt that that wasn’t as safe as having the posts sit 1.5′ in the ground. The control lines of the cement slab are just bricks with mortar. I figured I could just remove 3 bricks and dig to 1.5′ for each post hole. The concern was to not crack neighboring bricks and cement. Here’s how I managed to make rectangular holes with clean edges.
First, I drilled into a brick until I reached the dirt. This gave me an idea of how deep the slab was.
It wasn’t too deep.
I then used a cordless angle grinder with a diamond blade to score the perimeter of my desired hole. This was especially important so as to not crack the brick next to the hole.
You could also use a circular saw with a diamond blade.
I used a jack hammer to demolish the bricks.
I have the XtremepowerUS 2200Watt Heavy Duty Electric Demolition Jack Hammer Concrete Breaker which I got on Amazon.
It easily broke up the bricks into nice big chucks.
Below the brick was a layer of cement.
I broke that up, too, with the jackhammer.
The next layer was dirt.
I dug into the dirt using the Bosch Bulldog Extreme jack hammer and a heavy duty drill with an auger drill bit.
Result: nice clean hole. I’ll have to put back two bricks for each hole but that’s easy.