1. Watertight SubstrateEIFS can go over everything from masonry …
1. Watertight SubstrateEIFS can go over everything from masonry block to cement board to OSB sheathing. But you need watertight protection for the substrate, whether that’s a liquid-applied membrane like Sto’s StoCoat, coated structural panels such as Huber’s ZIP System sheathing, or an impervious layer
of housewrap.
Harry Whitver
2. A Drainage Plane If bulk water leaks in, it needs a pathway d…
2. A Drainage Plane If bulk water leaks in, it needs a pathway down and out. Some systems call for vertical stripes of adhesive to create the drainage gap (which avoids the problem of fastener penetrations); other solutions allow the fasteners, but require a drainage mat. Some systems use channel grooves in the back side of the insulation itself.
Harry Whitver
3. The Insulation Layer
Continuous insulation is the big energy…
3. The Insulation Layer
Continuous insulation is the big energy advantage of EIFS. Expanded polystyrene insulation can be adhesively attached or fastened with screws and washers. After the insulation is on the wall, it gets rasped to make a uniform surface that will bond well to the acrylic-modified cementitious top coat.
Harry Whitver
4. Water Management Flashing and waterproofing are vital to succ…
4. Water Management Flashing and waterproofing are vital to success with any drainable cladding. With EIFS, you need to pay close attention to the details around windows and doors, including head flashing at the top of openings and drain pans at door and window sills. At the base of walls, you’ll need drainable openings so water can exit.
The idea behind exterior insulation and finish systems (EIFS) is attractive: a continuous insulated skin that’s lightweight, versatile, and energy-efficient. Those advantages made EIFS popular in the 1980s and 1990s, but then disaster struck in the form of widespread moisture problems. EIFS jobs were plagued by poorly done flashing of penetrations and sealing of joints. And the system’s foam insulation and acrylic skin trapped moisture—so walls that leaked couldn’t dry out.
Lawsuits destroyed the market for EIFS in home building. But manufacturers have bounced back with new “drainable EIFS” that have backup drainage to let water out if it leaks past the outer skin. (The new methods also rule out using poly vapor barriers under the drywall, so the interior wall faces won’t trap moisture if the outer face does leak.) Building science guru Joseph Lstiburek, who as an expert witness helped seal the doom of barrier EIFS, is a fan of the new drainable version. And attorneys say the lawsuits have largely dried up and blown away.
Different brands of drainable EIFS use different details, and the industry says it’s a bad idea to mix and match. But here’s a look at the elements that the new EIFS methods have in common.
