Synthetic Stucco – Why Weeping Holes Are Important

Synthetic Stucco (actually known as EIFS) is a popular cladding among both commercial buildings and residential homes in Northern climates because of it’s superior ability to insulate a wall and manage moisture. The moisture management comes primarily from 2 important components of EIFS:

  1. The weather barrier (typically trowel-applied) that acts as a back-up defense against any incidental moisture that gets past the outer barrier
  2. The drainage cavity created by geometrically defined insulation (read: insulation with grooves in the back) and strategically placed adhesive

There are a number of important details that need to be paid attention to, to ensure the system performs optimally. It’s important to note that the drainage system will work even if the details are screwed up to some degree, just not optimally. What we’ll focus on here is the weeping holes though.

Stucco Weeping Holes

Stucco Weeping Holes on a commercial building

Weeping holes are simply gaps in the caulking that is installed at the base of an EIFS wall. The EIFS can terminate 8″ above grade (per building code requirements), above another material (such as brick or stone) or at the joint between floors. EIFS should be terminated with a flashing that is tied into the weather barrier with the use of an EIFS tape, so that water is diverted away from the wall, out onto the exterior surface. Caulking is then installed between the flashing and the EIFS termination (the underside of the EIFS), with weeping holes every 24″ (or per manufacturer specifications).

The caulking prevents excessive wind-driven rain, and/or insects from entering into the EIF system from the bottom. The weeping holes provide adequate area for air flow and drainage of incidental water, while being small enough to act as a deterrent to insects. There’s actually a study floating around somewhere that concludes that the ventilation within an EIFS wall is enough to create an inhospitable environment for bugs to nest.

The lack of weeping holes when caulking is present is strangely common – whether by fault of the EIFS contractor being improperly trained (or maliciously lazy – is that an oxymoron?), a site supervisor lacking the knowledge, or inadequate inspection from the manufacturer. An EIFS wall without adequate drainage from the bottom may suffer from:

  • Precipitate buildup at the caulking
  • Inadequate air-flow for ventilation

Both of which will generally shorten the life of the EIFS wall itself. Will a general contractor who is on the job to ‘get it done and move onto the next’ care? Not likely. The EIFS wall probably won’t fail within the GC’s liability/warranty period, and they probably have backlash against the installer or supplier of the EIFS system regardless. It’s more about ensuring that EIFS countinue to be seen as a reliable, effective cladding for the sake of the future of the industry.

Oh, and the person who ends up owning or using the building. They’re important too.

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  1. Brad

     /  April 8, 2012

    I’m sticking foam to osb board, at the bottom is brick . I’m using starter track, how far should I keep my track off the flashing covering the brick

  2. Admin

     /  April 8, 2012

    Hey Brad,
    This doesn’t sound like an approved EIFS installation, but following the performance guidelines from EIFS manufacurers should help.

    When using the starter track above flashing, not much space is required for drainage. 1/2″ should do.

    Don’t forget to apply a weather barrier (like Durock PolarBear) before adhering the insulation, and be sure to incorporate drainage channels behind the insulation.

  3. jonathan ursini

     /  April 9, 2012

    Hi Brad,

    I would recommend our PUCCS system (see under PUCCS). It’s designed for over OSB, using our Polar Bear as a air/moisture and adhesive. The insulation board has circles cut into it, that provide adequate drainage (this system is CCMC approved for both residential and commercial use). If you would like to discuss this further, I can be reached @ (416)881-3254 anytime.

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    • What is Stucco?

      "Stucco" is typically what people in the Toronto area use when they're looking for EIFS (Exterior Insulation Finish Systems, or "synthetic stucco"). We use the two terms interchangeably.

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