Under siding--OSB vs Ply?
 

I want to install a sheet under the Hardiplank siding--which is better OSB or Etx. Ply? What about cost diff? Thanks.

OSB will be more affordable and is pretty much what all the new builds are made w/.

Hello TaskBoy:
OSB is more eco-friendly too because it uses all of the log; there are no slabs cut off. I recommend it for the green effect.
Glenn

Hi Glenn, thanks for the green info. We are into supporting that if finances allow. Sounds like a good choice for us.

OSB is OK but plywood is the more premium quality product in my opinion. Take a heavy hammer to a piece of OSB sheathing and you can easily punch a hole, not possible with plywood. OSB can also suck up water much more easily if it gets wet, especially at the edges. This is most pronounced under roof shingles. A swollen board wont cause a a big issue with hardiplank.

see
http://www.inspectorsjournal.com/forum/uploads/Erby/2007112452818_DSC03531.JPG
http://www.rd.com/familyhandyman/content/19557/
http://www.extremehowto.com/xh/graphics/articles/art_60280_rightrooflead.jpg

Trees do grow back and plywood is generally made from a fast growing tree crop planted especially for wood products after harvesting. OSB is generally cheaper than ply.

One contractor I talked to today said he was going to go right on the studs with two layers of waterproof membrane under. Hardie's install sheet says you can go onto studs or onto 7/16 OSB--what would you folks recommend? Thanks.

Last time I did hardieboard I did

Studs - 1/2" OSB - Tyvek - tape seams - Hardieboard

The stuff is rigid but not that rigid IMO.

Add'l query...
 

I wanted to keep this related issue under the same thread...

If I put sheathing under the Hardieplank like OSB or ply, does the additional thickness now mess up french door mounting position or the measurements of the doors I'm to order/install. Or do I just get std. dimension (frame thickness) ones? Sorry but I am not familiar with how doors are installed (yet). What about the existing vinyl windows--will the siding stick out too far with sheath under? Thanks!

No issues - The doors will install after the OSB and before the siding. I would think you would be messed up on any jambs on the inside without the OSB.

Thanks. What about existing vinyl windows with adding OSB or even just leaving the existing ply siding in place--too thick then?