The Historic District

Will be completing the purchase end of March 2016. Two story, 2k sq ft, large covered porch with drive-through carport, two additions (kitchen/utility room), and detached garage/shop building. I am considering a new metal roof. There will be some areas of rafter repair and sub-roofing material replacement. My question is, can I leave the 2 layers of existing shingles, where no repair is necessary, and run the new metal roofing over it? It has true 2"x8" rough-hewn rafters, so I believe from a weight standpoint, it should be ok. It also appears a previous owner removed a wall (NLB) between the LR and DR. Prior to that, it had a 2nd layer of hardwood flooring added to the DR area. Now there is a tripping hazard. For correct period restoration purposes (and safety considerations), how wide should the new transition strip be? Thanks for any help.

Harleydvdsn, first off, welcome to the Historic District. I would suggest a third layer of anything on your roof would be a mistak in my opinion. I would be thinking about putting the wall back in, it just might be load bearing. Open concept in older homes can some times be a disaster waiting to happen.
Pictures would be nice,

Hey harleydvdsn99 welcome to the District

Thanks for the welcome. Gothichome, I know what you mean about a 3rd layer of any roofing material as not the being the suggested way to go, however, I'm thinking about the insulation factor for summer cooling. I restored a ca. 1900 home in Newport, RI in '97-'00 with a slate roof. Even though a professional home inspector and a dedicated slate roof expert looked at the place, and gave the existing roofing a solid rating, I ended up, while repairing a small valley, replacing a large section ($15k+). As I'm sure most restoration experts will agree, sometimes the proverbial can of worms will accompany old roofing tear-offs. If I could avoid a complete roof replacement on this project, I would. The interior wall was not load bearing, however, I am considering building a wide opening shallow arched wall with french doors where it was. I'm still going to have the flooring height transition problem, but it won't be as pronounced if a wall separates the two rooms. As time goes on, I will add some photos. Thanks again for the tips and warm welcome.

Harley, a veteran at the old home restoration thing. You already have learned the lesson of never pulling a nail because you know it never stops at just that one simple fix, or in your case, one slate shingle. Look forward to the pics.

Good chance your building codes will not allow a third layer of roofing material added.

Good point.

Welcome; as others have said we love pictures & will be interested to see your new old house!