House wrap is a general term used to describe an exterior weather barrier installed under most sidings.  They often are known by the names like, Typar, Tyvek, and BreathEZ.  The objective of a house wrap is to stop bulk water that gets behind sidings from getting to the wood sheathing, yet allowing water vapor to pass through it to the exterior which helps the wood wall system remain dry.  The International Residential Code and the Uniform Dwelling Code used in most states do not require a house wrap to be used on detached accessory buildings, as in a garage; however, Economy Garages installs house wrap under all field-applied sidings.