If I have a net network, will my prospective construction employer see it?

You have to assume anything you put on the internet has been seen. You can't assume that the construction executive you are speaking to in an construction interview has seen it. If they ask you about your blog or your on-line presence, be honest about it. They can and often do check for blogs and web sites. Many construction employers believe they can learn a lot from a construction executive's blog, so they search for them.