I can't speak for your builder, but there are a number of reasons to limit access to a homebuilding site. One is safety. Another is security. We've built lots of custom homes and provided owners a key for full access. Post drywall is the period when things tend to get damaged over a week-end when no work was being performed and the owners typically have no idea how it might have happened. We incur the cost to fix it. The worst offenders were a family with a young son who insisted on running toy trucks over the freshly painted walls every time they visited (it's known in our office as "free-range parenting." We limited their access based on our desire to actually complete their home and turn it over in good condition.
It sounds like your builder is willing to accommodate your visits during reasonable hours.
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coffered ceiling
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