Backwrapping, Edgewrapping and Terminating EIFS
No matter what type of wall-cladding is used on a home or building, it will stop and start at some point on the wall. These termination points are where water intrusion, if it’s at all possible, may occur. Extra precaution must be taken at these points to ensure that no water intrusion takes place, as this is typically what alludes to the common misconception that Exterior Insulating Finishing Systems are a form of wall cladding that is prone to leaking.
When the EIFS wall ends, it cannot simply be left as is, which would make the foam vulnerable to the elements and other undesirables such as insects. The appropriate handling of terminations, back wrapping and edge wrapping are desperately important for protecting the water-resistance and integrity of the whole project.
Edge wrapping and back wrapping, while similar, are two different methods of properly terminating an EIFS edge. Edge wrapping is the practice of extending the reinforcing fiberglass mesh along with the base coat over the edge of the EIFS and onto the masonry, framing or substrate. Edge wrapping is useful in certain situations but not in others, for example: edge wrapping requires access to the substrate, but if the EIFS terminates at a doorframe or somewhere similar, further extending the reinforced base coat onto the sheathing or substrate may not be possible. Edge wrapping is optimal when used with prefabricated panels, but definitely not for EIFS with drainage. Edge wrapping is also not suited for doing in advance or offsite, obviously because it must extend onto the substrate that is onsite.
Back wrapping is the practice of wrapping the edge of the insulation board with the mesh and base coat. Back wrapping does not extend all of the way to the substrate or sheathing on the other side. Despite this difference, both of the terms “edge wrapping” and “back wrapping” are sometimes used interchangeably.
Back wrapping can be done offsite if the EIFS will be installed into tighter spaces that would ordinarily make back wrapping difficult to do onsite, and the reinforced base coat can be wrapped around the foam insulation boards ahead of time.
Effective back wrapping can also be achieved by adhering the mesh to the substrate first with staples or adhesives, and further bringing it around the edge of the insulation board.
Embedded trim provides yet another way to terminate an EIFS edge. It’s far less used for edge termination in Canada than it is in Europe, the birthplace of EIFS. However, it’s far easier to install embedded trim in Europe because they use base coats that are nearly twice as thick as North American base coats, allowing the embedded trim to adhere much better.
Embedded trim has a special purpose when it comes to terminating the edges of EIFS with drainage. EIFS with drainage has openings along the bottom edges, large enough for water to escape through. Back wrapping or edge wrapping would be impossible on EIFS with drainage, because the water would have no way to leave the EIFS. Instead, embedded trim can be used, and cavities in the trim itself small enough for water to escape could be installed.
Aside from embedded trim, edge or back wrapping, other techniques can be used to effectively seal the edges of EIFS. Some of these include using liquid-applied sealants or coatings, as well as the implementation of flashing.
Proper edge termination will help keep the EIFS moisture-free, and proper edge termination lends yet another hand to EIFS no longer being referred to as a leaky wall cladding. It’s an undeserved reputation, and poor edge termination is one of the major ways water can get into EIFS.