Quick Answer Please!

[Byron Trantham]

I am installing OSB and noticed that it says "this side down". There is a smooth side and a rough side. I looked at the old stuff and it looks like it was either installed back wards or I don't understand "this side down. Which surface goes against the house, the smooth side or the rough side? I'm ready to install and waiting for an answer. Thanks.

[Bryan Nuss]

Rough side up when used as roof sheathing to provide a grip.

[Byron Trantham]

Rough side up when used as roof sheathing to provide a grip.

Bryan, this application is siding - covering the studs. Sounds like it doesn't matter. My biggest concern is wather protection. I'm in this mess because of rot. I have been working on this mess for three days now and I am "on my way back up" so I wanted to make sure that I was putting the preferred side facing the outside of the building. Thanks for your input. I attached a pic of the mess.

[Jeff Sudmeier]

Bryon,

I have always put the smooth side out when using the sheathing for siding. My thought was it seemed like the smooth side was more water resistant/less prone to hold water. Who knows, you are probably okay either way.

[Byron Trantham]

Bryon,

I have always put the smooth side out when using the sheathing for siding. My thought was it seemed like the smooth side was more water resistant/less prone to hold water. Who knows, you are probably okay either way.

Jeff, I agree. That's what I am going to do. Thanks

[Bryan Nuss]

The same type of resin is used throughout the OSB, so there is no preferred side for water resistance insofar as resin is concerned. The impression of the caul screen (which carries the oriented strands into the press and the board out of the press) into the flakes is what makes one side of the board rougher than the other side. The smooth side is that side of the board against the press platten. I built an OSB plant a few years ago, so am familiar with the process.

Here is the recommended tehnique for wall applications:

http://www.osbguide.com/faqs/faq15.html

[Steve Ash]

As a residential building contractor here is what I do and why. Rough side up for roof sheething...as someone said it provides a grip to walk on which is very important the steeper the incline, and the building inspector can read what type of o.s.b. I used as the thickness is stamped on the o.s.b.
On wall sheething I put smooth side in...again inspector can read what I used since I usually have siding and the roofing already on by the time the framing inspection is done.

That is the way I've been doing it for 16 years but as my former boss said "son, there are a 100 ways to build a house and none of them are neccesarily wrong...I just want you to do it my way"..so if you are not getting an inspection, then do whatever works I guess!
Good luck!

[Per Swenson]

Steve has it right,

From outside the building smooth side in.

When inside the building (subfloor) smooth side down.

As per NJ building code.

Per