Insulating Rubble Foundation
I am making slow progress renovating an old house in Maine–Rotten sills replaced. 10 tons of crushed stone shoveled in via basement window, new support piers and lally columns placed, dipple mat installed around perimeter and interior drain system installed. Now the walls. I have read multiple articles on the subject and still have questions.
Usually, I see pictures and diagrams that suggest first placing a vapor barrier, and then applying CCSF. I have even seen drawings with a vapor barrier, and then chicken wire to hold the foam. When I ask Stego if CCSF will adhere to their crawl space product, they cannot answer the question.
So, options–see attached rudimentary not-to-scale drawings and picture:
1. Just spray foam the rubble directly–I recently repointed the above ground sections, and hosed off all the stones to clean them–the drainage system worked. There are large gaps, but I bet it would hold. Some water pressure will be applied, less so when the ground gutters are installed at some point
2. Install vapor barriers first, Grace W&S on top and Stego crawl space below (this product comes in 5′ rolls that make handling easier) and spray foam just the sills and area above grade.
3. Same as option 2, but insulate all the way to floor.
There will be a 2″ rat slab poured with no insulation below. This space will only be used for storage and mechanicals. Not enough room for a ping pong table.
Thanks for any insight.
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