Vapor barrier on exterior wall???


Old 10-04-04, 08:44 PM
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Vapor barrier on exterior wall???

Hello, I am building a garage 18 x 20 and am going to install the 4x8 sheets of hardy board cement board on the outside. Was just wanting to get some opinions. I thought I should put something on the outside of the studs like felt paper, plastic, or something like that before I put up the cement board. The inspector says I dont need to. Now I am not going to finish the inside. As of now I am planning on just leaving the studs and all exposed on the inside along with the ceiling joists. Is there a reason I should use a moisture barrier or is the reason the inspector told me I didnt need it was becuase I am leaving the inside open and not sheetrocking it???? If that is the case and I was to decide I wanted to sheetrock it later, would the brown paper on the backside of the rolled insulation act as a barrier or do I still need to use something????

Also, if I should go ahead and put something on the studs what can anyone recommend???? I thought about the roof felt as that was recommended but it seems like it would tear easily. What about using the clear plastic that is thick and has the strings woven in it? Seems really strong. I appreaciate any help and advice anyone has. Thanks a lot

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Old 10-04-04, 09:16 PM
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A vapor barrier is always installed on the warm side of a wall.

Even though you plan to leave the wall open if you ever insulate the space and heat it,the wall will trap moisture and possibly be damaged.

You can use a product like Tyvek which is a building wrap that can be used on outside walls, but will allow moisture to pass through.

Now that I re-read your post do you mean to put the vapor barrier on the inside or outside wall?

If on the inside you don't need to untill you actually sheet it in.
Old 10-05-04, 04:53 AM
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Thanks for the reply. Yeah I was talking about the outside of the wall. This is my first project so believe me Im learning a lot. I wasnt aware that I could put something on the inside. I dont have any sheathing up on the ouside so thats where I was thinking about. This Tyvek stuff that you are talking about, do you know if this is something that I can get at a Home Depot or Lowes? Thanks for your help.

Old 10-05-04, 05:03 AM
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I went to web site for tyvek, and did a search for dealers stores in my area, and according to it, the closest one is like 50 miles away. LOL If by chance when I call around today and see if anyone actually carries it, and they dont, is there a similiar product that you can recomend? Unfortunately, since the insepctor originally told me that I didnt need anything for a detached garage, I did not offset my bottom plate with the concrete edge. I have it flushed up, so I dont think the foam board material would work. This is why in my original post I was looking for something like what you are recommending. A wrap. Thanks alot.

Old 10-05-04, 07:20 AM
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Even though code may not require sheathing or a weather barrier under Hardie Board siding, it is a better idea to install them.

You would do better to completely sheath the outside of the studs with OSB plywood, then install tar paper or a housewrap over the sheathing to prevent wind and sun blown water and rain from entering the garage.

Tar paper is far cheaper and as good a weather barrier as Tyvek.

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