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Community and Q&A

Weep Screeds Behind Manufactured Stone Veneer

Sawyer1013 | Posted in GBA Pro Help on

I would like to find some clear details or instructions on installing weep screeds and WRB’s behind stone veneers. I am particularly interested in the transition between a wood framed wall and a block foundation. The stone veneer would be running continuously from the wall over the foundation. I have had a building inspector tell me that they want to see a weep screed in this transition zone. This does make sense to me because this screed is being sandwiched between the foundation and wall veneer thus defeating its purpose. I think the inspectors are trying to use the logic behind brick veneer flashing in this zone and not realizing manufactured stone is a different animal with no air space between the wall and product. Most of the manufactured stone installation instructions are vague in regards to weep screeds and flashings. In fact the details I have seen show the screed as the final termination instead of this sandwich situation.

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  1. GBA Editor
    Martin Holladay | | #1

    I urge to to be very cautious with any design including adhered manufactured stone. Such installations have resulted in epidemics of wall failures — especially when the manufactured stone is installed over OSB — and the suppliers of manufactured stone have not yet responded to these failures with adequate installation details.

    My own advice:
    - Manufactured stone should only be installed over foam sheathing — never over OSB.
    - Between the foam sheathing and the manufactured stone, use two layers of WRB. The inner layer should be a three-dimensional drainage mat or a dimpled or corrugated housewrap that permits drainage.
    - I would be sure that the contractor who installed the manufactured stone had very good liability insurance, because many of these installations end up in court.

  2. Robert Latvala | | #2

    I would agree with you on the manufactured stone. There is a lot of it used in our area and for the most part being installed incorrectly. I am concerned that different building code officials are taking it upon themselves to recommend incomplete or partial solutions to the drainage plane issue.

  3. Pete Engle | | #3

    In the absence of good installation details from the manufacturers, the building officials generally have the authority to take it upon themselves to recommend solutions. If they had the guts, they would simply reject the use of this as an alternate material without adequate data to show that its performance meets code minimum requirements. Martin is certainly correct - adhered manufactured stone is causing some very significant building failures.

    Some of the manufacturers are starting to come around and post better details. Coronado Stone and Cultured Stone are two that have better than average flashing details. But IMVHO, neither of them yet acknowledges what Martin said in his post - these materials are trouble over wood substrates, and in most climates you're almost guaranteed to have building failures unless you use double WRB with a drainage gap and very careful (read: Designed and Specified) flashing details.

    But the short answer to your OP is: Yes, the stone needs a drainage detail and isolation joint where it transitions from the wood framing to the foundation. That detail can be very tricky.

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