rotten wood under window down to the sill plate

[tomita]

we bought our 20 year old vacation cottage last year, and now discovered rotten wood under the window sill,
 the damage goes all the way down to the sill plate (attached pic 1),
we discovered that the plywood floor ending is  damaged too (see pic 2 )
and that the outside plywood sheathing is missing, and the wood siding is old,
what we did
1. we cleaned up the rot,
2. replaced the sill plate (see pic 3)
2. patched the ending of the floor
3. replaced the framing
4. patched the window sill  and insulate the window ( see pic 4)

what we plan to do now
1. replace the floor joist (will be delivered tomorrow! )
2. reinforce the sill plate
3. put new insulation, repair the studs some more
4. seal the vapor barrier good again
5. replace siding where we took it off and paint.

WE don't know what to use for the missing outside plywood sheathing. as we are just patching the siding we can't add another layer under just a few boards.
BUT how do we isolate the old siding for this winter?? we are short of time, next week we have to get back to work.
We can plan to do a proper job next year.

We think there is similar damage under 2 other windows.

We didn't suspect anything because there is no smell of mold  and the interior walls are very nice, quality spruce (see pic 4)

What should our priorities be?
What can wait to be done after the winter? (window replacement comes to mind, other)
Thanks for advice

[lthenderson]

I don't think you are missing sheathing in just this area, it appears there is no sheathing anywhere. To me, the easiest way to fix this temporarily is to just fix it properly by buying some boards the same width as the rest of your siding and firing strips and patch in the area making sure to caulk the seams and slap on a coat of primer and exterior grade paint. I suppose you could patch it in by cutting a patch out of some treated plywood of the proper thickness but getting a good fit and having to buy an entire sheet for a small patch seems like more work than simply fixing it properly.

[tomita]

lthenderson: thank you
Good idea for temporary patching.
You're right there is no sheathing.
But when we replace all siding we should also add plywood sheathing all over, right?


 

[lthenderson]

I am not familiar with Toronto standards of building practices so I can't answer your question directly. I can say that lots of older houses are built without plywood sheathing. My house only has plywood sheathing on the corners and the rest is fiberboard. Sheathing was probably the next step in making houses more air tight. These days with house wrap doing that job more effectively, sheathing might not be necessary.

[tomita]

we did the patching and replaced as much rot we could, want to share some pics
lthenderson thanks for the advice, the house is in another province, different rules.
this issue was an eye opener and DH will go back and finish the job

[lthenderson]

Looks nice!