Making outbuildings and old garages habitable and protected against water
I’m working in Title 24 zone 3, and have several old garages that are slated to turn into conditioned residences. They have a variety of external cladding usually with 16″ OC dimensional studs, and often are built directly on the property line (no setback). Replacing the exterior cladding is a mess, in part because of lead paint, but for many reasons. Termites are a constant concern, and present in some of the outbuildings.
What would you put on the inside of those wall cavities to keep the old cladding? For energy code? For 1 hour fire rating in both directions? For longevity if the cladding is not replaced?
Typical construction is
* Dimensional studs -> 3/4 skip sheathing -> degraded tar paper -> wire mesh 3 coat stucco. The stucco is usually finished to below grade level.
* Dimensional studs -> tar paper degraded -> 3/4 shiplap / T&G.
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If you need fire rating, there are no options I know of that don't require pulling the cladding.
The one way that I have done it, I would check with your local building department, is to install a load bearing UL rated assembly inside the existing walls and treat the existing structure as your cladding. It does mean loosing a bit of square footage, but it is a pretty simple retrofit.
This has the added benefit of keeping the existing cladding well vented and would allow you to switch to something like light gauge steel construction if you are worried about termites. In your mild climate, there is very little energy saved with high R value walls, not worth the effort.
Sharpen your pencil and do the math but I doubt you are saving and cash if you turn the garage I am imaging form your description into a home.
Seems to me you will find it necessary to break up most of the concrete when you install the drains. Seems likely the current slab is maybe 4 inches above the low point on the property making the likely to flood given a heavy rain. I am imagining single car garages so the spaces will be tiny. If the framing is termite infested lots of it will need to be replaced. The existing window are likely unsuitable and in the wrong locations so you will be replacing and reframing. Over half of the siding will be new when you fill in the big door and flash the new windows and doors. Could you really sleep at night if you failed to remove 100% of the old lead paint knowing a child would be living there? I doubt the building inspector will accept any interior fire protection system and you may not have room on the exterior if you are truly on the line now.
For the same money you could build some very nice homes that would be much better homes that would cost less to operate never flood and be safer just farther away from the property line.
The question of landfill the outbuilding vs. fixing it up, depends a lot on the building. Some are fabulous multistory structures with artistry, history and using materials and techniques no longer possible to replicate. Others are cheaply slapped up garages with stucco right down to the termite level.
Some lots have plenty of space, others the 4' on each side makes the project infeasible.
Note that the State offers the described setback exception, but some local jurisdiction are permitting either conversion or brand new lot line residences, right now (Albany California is such an example).
Lead paint is harmless if encapsulated. This is well established. Demolishing it however can leave lead paint chips in the soil if done poorly, and that could create a future hazard. So yes, in a case by case basis, I could sleep very well on the lead paint issue.