I know I may get some flak from real carpenters for this little repair side-project, but here it is anyway....
I am gutting out my bathroom this summer and as in the past when tearing into this 1918 house, stuff gets found. Some interesting, and some sort of bad.
The bathroom was obviously shoe-horned into the place, likely in the 40s or maybe even later. I think the area currently occupied by the bath was originally part of the kitchen and the wood stove was probably located where the bathtub and a wall currently are.
When I removed the suprisingly single layer of newer drywall, I found that there was originally a much wider window from the current one. You can see it was filled in on the right side in this picture. There was no insulation below the window in 2 of those 3 cavities even though I found the plugged holes for the blown in cellulose in all of them. Someone must have forgot.

Any rate, it became apparent that back when that larger window was there, there must have been a water leak at the corner and ants had moved in

The tongue and groove sheathing boards were rotted and crumbly and there was "sawdust" too from the ants. I didn't find any actual ants dead or alive and everything was bone dry now so this happened long ago. In many spots, I could see the tar paper that covers the sheathing and also the siding. This house has another layer of siding over the original or else it would be rather drafty!
It seemed the ants were not content with the sheathing but also tunneled out this stud under the window sill. It was about 1/3 eaten up.

And it just got worse from there, ugh. The sill and even the subfloor had some damage. I was applying the screwdriver test to this and kept digging out crumbly wood.

Eventually, I got back to something mostly solid. I probably could have gone farther under the next to the left stud but it was solid enough and at some point a person needs to limit the project. The right side sill goes under those sister'd 2x4s and the adjoing wall so no real access. It was also mostly solid.


I am not sure what the concrete in between the floor joists is for, but suspect it was to lock the floor framing to the foundation. I don't think there is a plate on top of the foundation that the joists sit on, but rather they are just setting directly.
The ends of the subfloor were gone but the floor in the corner is not soft since there is a blocking between the 2 joists about a foot or so to the right since they't cut through one of them for the toilet drain. Good thing I guess at least for this problem.
The rim joist has damage but short of tearing 2 layers of siding and a layer of sheathing from outside to get at it; its not happening. Fortunately, its not eaten through and damage is pretty local to between those 2 floor joists. Ends of those were solid.
So, my repair was to fit in something to span across the the bad area between the 2 joists to fill in the rotted out sub floor and then replace that section of sill on top of that.


Once I had the sill replaced, I got a 2'x4' piece of 3/8" plywood sheathing and cut it to fit tightly between the 2 studs bordering the repair area. I then trimmed a 2x4 off by 3/8" and after prefitting it all in the wall I attached the sheet of plywood to the stud with screws from the "outside" and placed it in the cavity. The stud was nailed in at top/bottom and the edges of the plywood screwed to the old sheathing around the edges were it was solid.

One thing that occurred to me, maybe I should drill a few small holes in that plywood and fill up the cavities in the old sheathing under there with spray foam??
I also need to do something with the left end of that window sill board as it is floating and not connected to the stud a few inches to the left. With the interior wall boards removed it is not the most solid there right now. Once I get insulation in there, those interior tongue and groove wall boards will go back and eventually new drywall over that as it was before.
Interesting how "light" they built in those days but its still standing and pretty straight/square 100yrs later. There is no header above the window other than a horizontal 1x4. They must have relied on the interior tongue and grove wall boards for a lot of structural support, a main reason those are going back.
Another interesting observation. The cellar under this part of the house has fiberglass insulation between the floor joists and I had to pull some of it out to inspect this area from below. I noticed that the diagonal subfloor boards appeared to be reclaimed barn siding that was laid down with the "outside" down and inside up. A couple years back when I had the upstairs gutted to the rafters, I noted the roof sheathing boards were partially reclaimed from some other roof and had old tar paper and tacks facing inward. Also some had old concrete residue on them and must have been used as forms for the foundation I suspect.
I am gutting out my bathroom this summer and as in the past when tearing into this 1918 house, stuff gets found. Some interesting, and some sort of bad.
The bathroom was obviously shoe-horned into the place, likely in the 40s or maybe even later. I think the area currently occupied by the bath was originally part of the kitchen and the wood stove was probably located where the bathtub and a wall currently are.
When I removed the suprisingly single layer of newer drywall, I found that there was originally a much wider window from the current one. You can see it was filled in on the right side in this picture. There was no insulation below the window in 2 of those 3 cavities even though I found the plugged holes for the blown in cellulose in all of them. Someone must have forgot.

Any rate, it became apparent that back when that larger window was there, there must have been a water leak at the corner and ants had moved in

The tongue and groove sheathing boards were rotted and crumbly and there was "sawdust" too from the ants. I didn't find any actual ants dead or alive and everything was bone dry now so this happened long ago. In many spots, I could see the tar paper that covers the sheathing and also the siding. This house has another layer of siding over the original or else it would be rather drafty!
It seemed the ants were not content with the sheathing but also tunneled out this stud under the window sill. It was about 1/3 eaten up.

And it just got worse from there, ugh. The sill and even the subfloor had some damage. I was applying the screwdriver test to this and kept digging out crumbly wood.

Eventually, I got back to something mostly solid. I probably could have gone farther under the next to the left stud but it was solid enough and at some point a person needs to limit the project. The right side sill goes under those sister'd 2x4s and the adjoing wall so no real access. It was also mostly solid.


I am not sure what the concrete in between the floor joists is for, but suspect it was to lock the floor framing to the foundation. I don't think there is a plate on top of the foundation that the joists sit on, but rather they are just setting directly.
The ends of the subfloor were gone but the floor in the corner is not soft since there is a blocking between the 2 joists about a foot or so to the right since they't cut through one of them for the toilet drain. Good thing I guess at least for this problem.
The rim joist has damage but short of tearing 2 layers of siding and a layer of sheathing from outside to get at it; its not happening. Fortunately, its not eaten through and damage is pretty local to between those 2 floor joists. Ends of those were solid.
So, my repair was to fit in something to span across the the bad area between the 2 joists to fill in the rotted out sub floor and then replace that section of sill on top of that.


Once I had the sill replaced, I got a 2'x4' piece of 3/8" plywood sheathing and cut it to fit tightly between the 2 studs bordering the repair area. I then trimmed a 2x4 off by 3/8" and after prefitting it all in the wall I attached the sheet of plywood to the stud with screws from the "outside" and placed it in the cavity. The stud was nailed in at top/bottom and the edges of the plywood screwed to the old sheathing around the edges were it was solid.

One thing that occurred to me, maybe I should drill a few small holes in that plywood and fill up the cavities in the old sheathing under there with spray foam??
I also need to do something with the left end of that window sill board as it is floating and not connected to the stud a few inches to the left. With the interior wall boards removed it is not the most solid there right now. Once I get insulation in there, those interior tongue and groove wall boards will go back and eventually new drywall over that as it was before.
Interesting how "light" they built in those days but its still standing and pretty straight/square 100yrs later. There is no header above the window other than a horizontal 1x4. They must have relied on the interior tongue and grove wall boards for a lot of structural support, a main reason those are going back.
Another interesting observation. The cellar under this part of the house has fiberglass insulation between the floor joists and I had to pull some of it out to inspect this area from below. I noticed that the diagonal subfloor boards appeared to be reclaimed barn siding that was laid down with the "outside" down and inside up. A couple years back when I had the upstairs gutted to the rafters, I noted the roof sheathing boards were partially reclaimed from some other roof and had old tar paper and tacks facing inward. Also some had old concrete residue on them and must have been used as forms for the foundation I suspect.
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