Drywall or multi visit scheduling

Home Remodeling company here. 

I relate to the difficulty of scheduling visits. For us, we find that we can't accurately estimate the time it takes to complete certain jobs. This is partly because our services are widespread, and because of the roadblocks often seen in construction.

Currently, our method to counteract this is to make all current jobs constantly active (i.e. one visit per job is scheduled for a month long.) That way, our employees will always be able to clock in, and we don't have to manually shift the schedule around every time we hit a roadblock.

I know there has to be a more effective method though, especially when considering scaling the business. If anyone has advice, please let us know!