In the US, building permits are public record, if the jurisdiction requires plans to be submitted as part of the permit package, they also become public record. In the last 10-15 years many jurisdictions have moved to filing everything electronically (either scanning in the permit package or having everything submitted electronically to begin with). Many of these jurisdictions also make this available on their websites, making it that much easier for the public to find. It is possible to find this for many major cities in the US by going to their building department's website.