Brought purchased my house was remodeled and T1-11 was used as the new siding. They installed T1-11 over the existing plywood sheathing so I have double thickness plywood. Due to the windows being installed then over the T1-11 it is not easy to just tear it off, so my plan is to just re-side over the T1-11. The problem is on the gable end they did not install T1-11, so I just have the original plywood us there causing a difference of about a half inch.. So I have two options to flush out the siding, I can slap up another layer of sheathing to make the gable end the same thickness, or I can just add 1/2" furring strips. Furring strips would be much easier and somewhat cheaper in my opinion, but I am not sure what type of end product I will be getting with this. I guess it just seems very strange to have nothing solid behind the siding.