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1830 shed, bottom sill replacement

Greetings to all --

I have attached some photos of one of the sheds on my property in upstate NY. It's a very long shed, about 12' wide x 65' long. Date is circa 1830s/1840s.

There appears to be an above ground stone foundation, covered by 4" concrete slab. The bottom sill is rotting or missing in some sections, and I want to replace it. The very rear of the shed is all concrete, and about 3' below grade (the section where it starts to be stone and concrete is visible in one of the attached photos).

Here are my questions:

1. I understand that in order to perform the repair, parts of the structure will need to be jacked up. Inside the shed, the measurement from the concreted slab to the underside of the upper sill is about 73". From my brief research, this seems too short to get a jack post, bottle jack, and some materials under the bottle jack to spread the load. Perhaps a solution to this would be to instead jack from the outside, after removing the upper exterior wood to gain access to the upper sill.

2. For reasons if toxicity and aesthetics, I don't want to use pressure treated lumber. I'm wondering what species of wood might be recommended. I am considering a non-PT variety that I would treat with CPES.

3. The bottom sill measures 5" x 5". It's not clear to me at this point if the bottom sill is anchored to the slab, but in some areas the slab is so thin, I doubt it. If it is required to be anchored, then how might one anchor such a thick piece of wood to the slab?

There is a small chicken coop on the property that is in the same state. I intend to fix this structure first. It may reveal information about how the larger shed was constructed.

Would appreciate any and all feedback on my situation.

Thanks in advance.


Re: 1830 shed, bottom sill replacement

Cedar, heart pine or white oak could all be used as sill stock, and be left pretty much untreated. Use a water barrier against the concrete to keep the moisture out of the wood. Or, seal the bottom edge of the sill with marine epoxy.
To jack, you could easily bolt on a ledger to the framing (through the siding with 5/16 lags or spax screws.) and place the jack posts and support timbers under the ledger.
The ledger could be bolted inside just as well.
With a shed there's not a lot of weight to carry, and it's temporary, and hopefully you will work in 16' or other manageable sections, at least til you get the hang of it.

Re: 1830 shed, bottom sill replacement

S_M --

Thanks so much for the information.

You mentioned a "water barrier" could be used between the concrete and the bottom of the sill. Might you have some suggestions in this regard?

Thanks again --


Re: 1830 shed, bottom sill replacement

The barrier could be ice & water shield (a roofing product) or the self-stick bitumen tape used in window installation; it's basically the same stuff, but with different textures. It's tarry, sticky, and waterproof. If you painted the bottoms (and lap joints) of the sill stock with epoxy, that would be just as good.

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