I have a question on resources for learning about the history of romex wiring and drywall, so that I can better identify the decade in which they were likely installed. Since this type of knowledge is something inspectors use every day, I thought this would be a good place to ask.
First, though, the saga that has led to this inquiry:
I am a residential designer in Portland Oregon, and I created permit drawings for a project that included adding a bath to an existing second story and removing some interior bearing walls. The drawings were done for a developer/house flipper who had just purchased the home. I have done hundreds of similar projects, and I have learned to never assume that any improvements to a home were legally permitted. On this project, the issue of whether the upstairs was legally habitable space was discussed with the owner at our first site meeting, and I was assured it was. As has happened before, when I took the plans into the City for submittal, I was told that the second level had never been approved as habitable space.
The home was built in 1906, and the second story improvements included ½” x 48” drywall, T&G subfloor with particle board on top that ran under the partitions, 3-1/2” x 1-1/2” studs, small aluminum sliding windows, fiberglass batt ceiling insulation, and wiring that was plastic sheathed NM 2-wire with ground, among other indicators that said to me that the improvements were from a late date. The electrical outlets included a mix of grounded and ungrounded plug types.
At permit submittal, I was told by the plans examiner, based on my description of the existing improvements, it was very unlikely that the attic could be grandfathered-in by way of a special inspection the City offers in such circumstances.
When I informed the owner of our inability to proceed with the project as documented, he promptly cut off all communications with me and did not pay me for my work. The owner apparently paid for the City’s special inspection and got it grandfathered-in. A week after my initial attempt to submit for the permit, the owner applied for the permit using a new, completely redrawn, set of plans. Not surprisingly, these plans did not include my structural details and calculations for the removal of interior walls.
I had told the owner that it appeared to me that the improvements were made in the 1960’s at the latest, but, clearly, the City’s special inspector thought the work was from a pre-code era. I have been told by City officials that the 1940’s and earlier improvements are usually grandfathered-in. To help my due-diligence in the future in judging the age and legality of existing improvements, (and this is the question of the post) does anybody know of a reference for the history of when cable sheathings changed and when standardized sheetrock sizes changed? Or perhaps someone here knows the history of these or has discussed this in a previous thread?