How-To Install New Drainable EIFS

New “drainable EIFS” that have backup drainage to let water out if it leaks past the outer skin.

1. Watertight Substrate
EIFS 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.

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.

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.

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.

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