questions on sheathing, house wrap, siding

[Andrew Thuswaldner]

I have to replace the sheathing and vertical wood siding on my garage because it was not done properly when the original owner converted the carport to a garage sometime in the 70's. Water has leaked in over the years and is rotting the sill plate and the lower part of the 2x4 studs.
My questions are:
What thickness of OSB should I use for the sheathing? I imagine something close to 1/2" but I'd like to know what the code is.
My garage floor is a slab on grade and there is good drainage all around but I don't have more than 3" from the top of the slab to the ground so are there any other precautions I should take such as flashing on the lower edge?
Concerning the house wrap I know I should tape it with that 'red tape' but what is the effect of all the nail holes that I am going to put in the house wrap when I install the siding?
I want to use vertical wood siding (likely pine) to match what was there before and the rest of the house but is vertical siding worse than other options at keeping water out?
Any recommendations on what house wrap to buy?
Any other tips you want to give me would be most appreciated.
Andrew

[Brian Effinger]

Andrew - 7/16" osb is commonly used for wall sheathing. If I were you, I'd also replace the sill plate and studs. Use a pressure treated sill plate. I've attached the detail I put with my drawings for detached garages. One thing you could also do is use 1/2" plywood sheathing instead of osb, and install a 6" strip of pressure treated ply around the bottom of the wall.

[David G Baker]

I just had my front porch enclosed, the contractor used 24 inches of 1/2 pressure treated plywood and then the rest of the sheeting is 1/2 inch OSB. The sill plate is pressure treated with the roll foam under it and a lot of silicone between the roll foam and the concrete slab. The pressure treated plywood is about three inches below the concrete surface.
Do replace the sill plate and the studs while the wall is open because if you don't do it now you will be doing it soon.

[Michael Wetzel]

Replace everything while you have it ripped apart. Use a PT sill and put a layer or 2 of tarpaper between PT and the concrete floor. This will help prevent the moisture in the concrete from pulling up into the wood. Intall 1/2 OSB and use a spacer to keep it 1/8 to 1/4" above the concrete floor. Fill the gap with silicon caulk. Install Tyvek on the wall and tape any seams. If you buy a short roll of tyvek, make sure you start at the bottom of the wall and overlap over each course. Tape all of the seams with tyvek tape.