Window leak? subfloor repair

[MattInAR]

I'm in the process of replacing carpeting and I found water damage on the subfloor. Its under a window and next to an outside corner. I also found water damage on the drywall which looks to be wicked up. I've removed the damaged drywall and I'll have to remove and replace the damaged OSB subfloor as it is crumbly in spots. My Question is how can I tell if the water is coming in from the window or if its coming from the outside corner? Also how difficult is it to replace the subfloor in a corner as the walls seem to be resting on it?
Thanks Matt

[Greg]

Matt, As long as you have the sheetrock off, pull the insulation back and see if you can tell where the warer is coming from. In your situation it could be coming from either or both places.

As for the sub floor, you can either spend the time and chisle or grind the subfloor out from between the joists and wall studs or you can sister a joist in and set the new subfloor on that. Greg

[MattInAR]

Thanks Greg.
Then there won't be any problem with leaving that bit of damaged subfloor that is stuck under the walls ?
I was worried that the walls might some how sink down in the corner.
There is only about 2 feet of water damage along both edges. I'd rather sister in a joist and a couple of cross pieces since I'll have to do it on the other two edges of the patch.
I pulled the insulation out already to make sure it wasn't wet. I believe the water is wicking in along the subfloor from a bad repair to the corner piece of vinyl siding. I fixed it right and I hope that will be the end of the leak.
It rained all last night and I didn't see any water or feel any dampness around or under the window frame.
I can't tell about the corner just yet since that area of the floor is stil a bit damp from the last two weeks rain.

[Greg]

To do the job "by the book" the old partical board should be removed, but I think that if the old floor that is left under the wall is still solid you will be OK sistering in a joist. If it is already mush it is easy to remove. Greg

[DigitalDreams]

I had a spot in my bedroom that was the same way a window frame had leaked it had run down inside of wall and wicked into subflooring
and about a 2 foot section out from wall was spongy.

What we done was cut out the floor on that section 2 floor joists out and replace it with green treated outdoor plywood (thats what I have done in fact every place I have had to replace flooring due to rot.

We left the osb that was under the walls in there because compression will keep it from expanding and then did like Greg said
, sistered a green treated joist to the existing joist well past the damage points.I did the same under my toilet when we found the floor around it was soft.

[MattInAR]

Thanks,
I'll leave that subfloor in then. I don't need more work. I just found a leak under the shower .

[nattydreadlocks]

If you are afraid the wall will some day sink, before you box in your opening, nail a piece of flooring to the bottom of the soleplate and double up your headers.

[Brenda (OH)]

Can you use a garden hose to direct water onto the roof, and then watch if it comes inside the wall, vs spraying the water onto the window and see if the water then shows up inside?

Brenda