Sometimes we remove the former from underneath the arch before the bridge is completed.
In the case of Hubb Creek Bridge one of my students, a landscape instructor at Fanshaw College in London had to leave before the two week dry stone bridge workshop was over.We knew that all the voussoirs in our bridge were fitted well and firmly locked in place with wedge stones and pins.
The arch was tight.
Almost all of the work on the sides (tails? ) of the bridge had been completed but not the top.
I knew the bridge would be able to hold itself up even without the addition of weight to the top, though this does give it even more strength.
My student was eager to see the form taken out before he had to go.
We smashed out the supporting cement blocks, it dropped down a satisfying 3 or 4 inches.
The bridge didn't move a fraction of an inch.
Next we unscrewed the scabbed plywood holding the two halves together, removed many of the lose 2x4s over the top of the form and then carried the right half away.
The second half gave us a bit of a battle as of the form was still pinned at the north east springer.
With pry bars and some good whacks with a sledge hammer the former came free and four of us removed it.
The arch looked very strong and beautiful. there was no concern that it might fall down.
It do remember it looking a bit anorexic though.
What was left to do in the next two days was to add more 'meat' over the arch in horizontal rows of builder stones and to build up the walking surface, add gravel,then landscape fabric, soil and turf.