Antique house #1: Cedar Roof
I will likely be taking on a crazy project in the next few months – buying an old house in Rhode Island, and improving it, on speculation.
The general scheme is to
–Do minimal work on the older (about 325 years) portion of the house,
–Expand/rebuild the newer (about 115 years) section with modern kitchen, baths, windows, etc.
— Remove ugly garage, breezeway, and dormer.
With luck, the major work on the old portion will be replacing the decrepit asphalt roof with cedar shingles, or something similar, with as little change as possible to the existing framing and sheathing (except removing the dormer, and perhaps adding a skylight or two). The attic is plastered, so inspection of the roof deck is impossible without removing the shingles. Presumably there is no insulation, and adding insulation within the roof assembly would seem to be a non-starter. I have not yet had “the talk” with the local Building Inspector, but anticipate that energy codes will not be an issue.
My current thinking is to:
–strip the roof, remove dormer
–add a layer of sheathing – either rough-sawn boards (diagonal?), skip-sheathing, or plywood.
–consider 2″ or so of insulation board
–another layer of sheathing – either plywood or furring spaced 5″ OC
–if plywood, some kind of ventilation/drying spacing or fabric
–cedar shingles, 5″ exposure
–site-built wooden gutter, lined with (?)
Roofing felt, or ice & water shield would likely be a good idea, but where in the assembly? Over the insulation? Under it? Certainly not too close to the old structure, or to the cedar shingles.
Fasteners are also an issue – I would hope to minimize intrusion on the original rafters – which are presumably spaced unevenly anyway.
Insulation board likely polyiso, though the house is very close to a big manufacturer of “Aerogel” insulation. There were some interesting discussions on this product on GBA recently, perhaps I could sweet-talk my way into some product…
So many issues, and this is just the start! I would appreciate any insights or ideas…