u/Gbd_does_reddit — reddlx

A corner of my house has old growth redwood still plate (true 2x6) and bottom of cripple wall (true 2x4). That are below grade and have partially rotten. Most of the damage is the sill plate, but I expect some stretches of the 2x4 also need repair.

Fixing the grade issue is another thread.

When I have to replace both layers of 2by with PT, I think I'm best served by trimming the studs short to fit a 2x6, then a double layer of 2x4 to make up for the modern lumber dimension mismatch. (Yes?)

Is there a better way to deal with portions where only the sill plate is affected? I predict a 1/4" to 1/2" gap to resolve and I would prefer to not have to do the same extra layer trick, it being more intrusive.

Tldr: portions of my rotten sill are below grade and I'm looking for options to improve the situation.

I'm working towards an earthquake retrofit of my home. Adding bolts between the sill to the foundation. The back wall of the still is below grade, which is a concrete patio. This is sketched above. I don't have perfect knowledge of the dimensions of the exterior concrete relative the sill, only that it is above the sill.

Several feet of the still are rotten away enough to undercut the 2×4 blocking. The rot runs into the corner and several feet down the next wall line. The second wall line is dirt, that is also above the sill for several feet.

I have to replace the sill and I've found enough videos and explanations to make this sound tenable.

What I'm unsure of, is how to improve the exterior interface to extend the life of the replacement. I'm thinking to add a recessed drain channel to keep water away. But this does not solve the ground contact of the sill (and possibly siding.)

Around the corner at the dirt exterior there is about 12" of parging over the siding by the previous owner. I assume this will crack off when I deal with the sill and would like to do better. There is also moisture coming through the concrete in that corner that I would like to stop.

Appreciate direction.