Can I ask a UK vs US question?
How tough are your permissions and licences for this kind of thing?
We now have a thing called permissible development that essential means if you want to extend your home or add outbuildings, then there's a bit of simple maths and some height limits, but if it meets the rules, you can just build. If you go over the limits, the you need to apply formally and the price gets pretty high for the necessary planning with no guarantee of success. How does it work where you live?
Pretty much the building of any kind of formal structure requires a permit. I think there's a size limit to sheds where you don't need one, but bigger ones you do.
Anything that will have power going to it, even a small shed needs a permit.
The permits for minor builds are pretty straightforward...you give them your basic plan, they look at it, and give you the permit...done.
Anything that has to meet certain building codes will require inspections during various stages of the build process.
In my case, I needed a permit, but I also needed to get an area variance, because I was beyond the minimum side set-backs to my neighbor's property, even though the neighbor was OK with it. So I had to apply for a permit, have it denied...then apply for the variance, have it approved...then reapply for the permit w/approved variance.
After they do the footings...the inspector has to come by and approve. Then they will put up the outer foundation wall, and again inspection follows...then finally the slab, and again inspection (I believe). After that there is the framing, and inspection...then the electric and inspection...and then the insulation and inspection...and then I think there is a final inspection before the Certificate of Occupancy is given.
So yeah, a lot of steps...but once I got past the variance, the rest is now pretty much straightforward, considering that I also had an architect do certified drawings and engineering specs, and my contractor is fully licensed...so the inspector coming by will be formality at most, and they all know each other, so probably little chance that there will be something not up top code, etc...but if anything comes up, the contractor will remedy as needed.
Bottom line...they need the individual inspections approved in order to move forward with the build...so everyone is eager to do what is needed to get the job done, and move on.