This spring I plan on installing vinyl siding over my existing T1-11. I do have a few questions due to the way the T1-11 was installed. I'll try my best to explain. I have a two story home. The top sheet of T1-11 overlaps the bottom sheet probably by a couple inches. So it is not a true "flat" vertical surface to work on. If I decided to install vinyl over the T1-11 the way it is now... would this be noticeable? OR, should I install foam board or plywood the thickness of the overlap to make it a flat surface?

ducsauce, it would be noticeable. Myself, I would trim the over-lapping couple of inches off the top pieces of t1-11. Chaulk a line and set the saw depth, and nail the new edge in tight. Good luck

I just wonder if they nailed a furring strip at the very top to bring the top piece of T1-11 plumb with the bottom, does that make sense? Will that be a big deal? I don't think that would be THAT noticeable, if at all.

The ends of my home have three pieces of T1-11. The corner wood trim is also overlapped? Is this common?

ducsauce, I doubt they used a furring strip, if they did I would take it out also and fill the space to plumb. The overlapping trim is normal, you need to remove the trim prior to installing your vinyl corner. Are you planning on using house wrap?

I meant they may have installed a furring strip up top behind the upper T1-11 panel to make it plumb with the bottom one. If they did and I cut the overlap where they meet like you stated in the previous post, the two panels still wouldn't be on the same flat plane, right?

Sorry if I misunderstood.

On lower part of building, install 2'' wide plywood strips the same thickness as T1-11.This will give u the same plane as the top. Lay the stripping out 16'' on center.

OR

U can use foam insulation that is the same thickness as T1-11.

Chuck

Your saying the top sheet of T-1 11 has been furred out completely, then do as Chuck suggested. I thought you meant they had placed a single strip were the two sheets meet. Sorry for the confusion and good luck