The debate regarding housewraps and vapor barriers will get you as many responses as there are participants. The question to wrap or not depends a lot on the following: What is on the interior walls? Is there a plastic vapor barrier to stop the outward flow of moisture through the walls? What is the room used for? What type of siding is being applied? What material is the sheathing? Are you paying for Tyvek? (It aint cheap) A general rule of thumb is that the exterior building envelope should be 3 -4 times more vapor-permeable than the interior. Therfore, any water that may find it's way into the wall cavity will be able to evaporate effectively. Tar paper has been an effective air/vapor barrier for many decades. Just because of newer products doesn't necessarily mean the older ones failed. I have worked on many fine homes that used tar paper. I am currently in the process of installing vinyl siding on my own home, and I chose Tyvek, merely to seal against the drafts and act as an effective water shield. Vinyl is hung loosely and therefore needs the addition of a barrier that will make up for all it's shortcomings. If I were installing brick, I'd no doubt, use tar paper. My opinion is that something is always better than nothing, even though it contradicts that of the post below. Good Luck.