I-cut vs. modified I-cut in housewrap for window installation
Preparing for window installation where the housewrap has already been installed and we will use Dupont FlexWrap for the sills.
Dupont’s instructions specify a standard I-Cut in the housewrap where the bottom is cut flush with where the sill will be, but it says that a Modified I-Cut is also acceptable.
Joseph Lstiburek shows in his instructions the Modified I-Cut which involves folding the housewrap inward at the sill so the FlexWrap would go on top of the housewrap.
I’m thinking that the pro of the Modified I-Cut is that the window itself is holding down the housewrap so water can’t likely get behind the housewrap, whereas the I-Cut relies more on the adhesiveness of the FlexWrap to stay attached on top of the housewrap to prevent water from getting behind it (although the nailing flange will also hold it)
But for the Modified I-Cut, if you are not attaching a sloped sill piece on top of the housewrap, isn’t the FlexWrap basically just attached to the housewrap, not to the wood buck itself? It seems like you would want the FlexWrap actually stuck mostly to the wood buck.
Have people found one way works better than the other? Thanks.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part