Stone and Stucco

InSoFast panels are ideally suited as a drain and dry insulation board for use under traditional stucco and thin-veneer stone applications. The panels utilize tongue and groove edges to provide a smooth continuous insulation substrate and include built-in studs for lath attachment. The InSoFast panel has drainage channels which are flashed to drain bulk water.

Flashing, Weather Resistive Barriers, and Concrete Sealers


It is important to properly flash and seal all penetrations through the InSoFast panels. See stucco manufacturer’s specifications and details which supersede the generic InSoFast details.

For wood or steel framed structures, InSoFast panels must be installed over sheathing with a weather resistive barrier. The weather resistive barrier must be properly sealed and flashed so that bulk water can move down the drainage channels of the InSoFast panels and exit out weep screed or drains at openings, penetrations, and bottom of the wall.

For concrete or masonry CMU walls, follow local building codes and stucco manufacturer’s instructions for proper flashing and sealants. Make sure to properly manage bulk water from the drainage channels into weep screeds or drains at openings, penetrations, and bottom of the wall.

Lath Attachment

Attach lath to InSoFast studs using #6 to #8 sharp-point, coarse thread screws.

Consult local building codes for screw type, spacing, and wind loading while following stucco manufacturer’s specifications and referencing InSoFast testing noted below.

  • Tod DuBois

    Can someone expand on the difference between EIFS siding Systems and InsoFast? I’ve chosen InsoFast for a Northwest install with stucco over it and the locals think I’m crazy. Would be great to have data showing that InsoFast is not an EIFS siding System and that stucco over InsoFast will last 50 plus years in the great NorthWest.

    • First things first! InSoFast is NOT “EIFS!” You are fine, and you made a good choice.

      • The InSoFast panel is a dual rainscreen moisture management system. Unlike the barrier EIFS systems that InSoFast is being compared to, if and WHEN water gets in, it will get out before it causes problems. So there is no need to get “freaked out.”
      o An important thing to consider is that any building product will fail if it is installed incorrectly. The details matter. The linked article below, is a study that outlines the potential problems that one can encounter using stucco as an exterior facing material and finish.
      • Oregon Residential Specialty Code (ORSC), Section R703.1.1 addresses these problems by requiring a rain screen system. The InSoFast panel has two rain screens incorporated into its single panel. It has been tested, and exceeds the Oregon requirement.
      o The drainage report, Drainage ASTM E2273-03 101692671MID-008, is attached to this email.
      • There is no simple, straight-forward answer to your question, and it can be long, technical and boring. It would be best if you called, unless you love reading technical white papers about vapor pressure, absorptive claddings, and rainscreen. If that is the case, I can provide you with a link to these papers.
      • EIFS is not really prone to failure, as much as people believe this to be true. While EIFS have had many failures, these systems have had billions of square feet of successful installations worldwide, and in every climate zone, even temperate coastal rain forests like Newport, Oregon.
      • The EIFS industry has done millions of dollars’ worth of research resulting in the conclusion that centuries of experience have long taught: when water gets into the wall it will cause trouble if it doesn’t get out. InSoFast was designed to address this known conclusion. InSoFast is a dual rain screen system, and, when the water gets in, it will get out.
      o “Rain is always prepared to wreck mischief….by its persistence it undermines the whole strength of building, until it eventually brings ruin and destruction to the whole work.” Leon Battista Albreti (1404-1472)
      o “It is very commendable in great fabricks, to make some cavities in the thickness of the wall from the foundation to the roof, because they give vent to the wind and vapours, and cause them to do less damage to the building.” Andrea Palladino (1509-1580)
      • More Research links below.
      o The Minnesota Lath & Plaster Bureau has published a paper that discusses the best strategies for plaster coatings over continuous insulation. It points to a 3 year study conducted at the Oak Ridge National Laboratory which concluded that “Exterior Insulation Finishing Systems (EIFS) with Drainage outperformed all other wall materials in terms of moisture management, while maintaining superior thermal performance.” Study Report
      o The Minnesota Lath & Plaster Bureau point out in the report that a “promising new product” called InSoFast which addresses all of these key points and greatly simplifies a stucco installation due its built-in attachment studs for lath and moisture drainage systems . You can read the paper here.
      o BA-1406: Final Measure Guideline: Incorporating Thick Layers of Exterior Rigid Insulation on Walls
      o The Cold Climate Housing Research Center (CCHRC)