Sealing crack between sill plate and foundation – GreenBuildingAdvisor

Hello!

I live in a 100-year-old house in Portland, OR.  There’s a basement (half of it you can stand in and the other half requires hands and knees).  The sill plate is Douglas Fir and the foundation is concrete but a little crumbly. There is no capillary break and quite a few areas with unevenness where the foundation meets the sill plate. In a few spots I can see light from outside.  Most places around the perimeter have a small gap (~1/8th to 1/16th inch) but other spots have a half inch to one inch space between sill plate and foundation. On the north side, for instance, the sill plate was pulled up and back because the foundation was leaning outwards. I had another post installed to take weight off that side but the gap remains.  The sill plate sits about 2 feet or 2.5′ above the ground and then 8-10′ or so above the floor of the basement (it’s sloped). The sill plate looks good in most places and isn’t spongy.  I’ve become familiar with this part of the house because I will be installing 10″ Universal Retrofit Foundation Plates and want to do something about the gap before I install these, making those areas of the sill plate-foundation interface inaccessible.

I’ve read the Q&As I could find here to figure out what to do about air coming through these cracks.  I don’t think I’d be able to slide any sort of solid capillary break material into this space.  I see there is reference in the answers to Zip liquid flash and various adhesive tapes as well as spray in foam, but from what I read, it seems a polyurethane caulk with a closed cell backer rod (where necessary) would be the best thing for me to use?  

Thank you.