Here is my first attempt at making a stone arched bridge out of lightweight Thermalite or Celcon building blocks.
First, mark out your arch. I used a 10 inch plant pot as a template.
Next drill through as far as possible with a decent sized masonary drill - no need to use the hammer function, it would probably shatter the block into many pieces. If your drill is shorter than the block is deep you will have to mark the arch on the other side and drill again.
Using a padsaw cut through between the drilled holes.
And voila (that's yer actual French!!) - an arch.
Using the padsaw smooth out the crenelations (is that the right word) between the remains of the holes.
I marked the stonework freeform with chalk.
Using a straight edge and the padsaw the horizontal lines were easy to scribe.
The vertical lines were a little more fiddly but I used a set square and a small, old electrical screwdriver.
Because the bridge will only be seen from one side the reverse was left blank. I was able to get to this stage in just over an hour
First, mark out your arch. I used a 10 inch plant pot as a template.

Next drill through as far as possible with a decent sized masonary drill - no need to use the hammer function, it would probably shatter the block into many pieces. If your drill is shorter than the block is deep you will have to mark the arch on the other side and drill again.

Using a padsaw cut through between the drilled holes.

And voila (that's yer actual French!!) - an arch.

Using the padsaw smooth out the crenelations (is that the right word) between the remains of the holes.

I marked the stonework freeform with chalk.

Using a straight edge and the padsaw the horizontal lines were easy to scribe.

The vertical lines were a little more fiddly but I used a set square and a small, old electrical screwdriver.

Because the bridge will only be seen from one side the reverse was left blank. I was able to get to this stage in just over an hour

