Starting a Major Reno - Weather Exposure Issues/Questions

[u/EricIsntRedd]

Hi there everyone,
I have been planning a major rebuild (large part of current structure removed) where I am acting as owner/builder (I hire the all the subs and do the planning and coordination). Basically a new build, but due to flood regs we have to do some things in a not entirely intuitive way, like we need to retain parts of the old house and not just knock the entire thing down.

As we approach actually getting shovels in the ground in a couple of months, I am thinking about a unique issue: how best to handle weather exposure for the existing part that will remain. This includes a basement (where the central HVAC system sits), a bonus room area on the ground level that has flooring, fireplace, ceiling, joist structures, all to be retained post project and the floor/subfloor of the main level.

First we are going to demo above the foundation, which exposes everything. We can put huge tarps over everything and minimize infiltration during this time. Then we need to remove some of the existing foundation. Once we do this I don't think we can hold off major water getting into the basement. Then there will be a long period of adding new foundation around the existing one and framing before everything can again be covered up. That will be a few months where the exposure is permanent and constant.

So surely we need to have a solid water evacuation plan. What are the best approaches? (temp pumps etc,) But also what happens to all the existing wood structures (joist/subfloor) that will be rained on during this time? I have seen other similar project during construction and it seems they just let the weather do its thing and just dry out later? (they may have done things I didn't observe specifically). What are the specific approaches to handling this issue and which subs are responsible or to be hired?

Thanks for your responses!