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Weep screed behind natural stone cladding

I. Wilson | Posted in GBA Pro Help on

I was wondering what if any sort of air space or water run-off space I would need to put behind a natural stone wall. I have read so many different ideas that range from not needing one to needing one.

I live in northeastern Ontario CAD. and our winters can get quite severe. At present I have a natural pine siding on one wall and want to tear it off and apply a natural stone veneer. The stones are directly from the ground and are mostly granite.

I understand all the present needs of an appropriate footing for their weight as well as the, typar house wrap lath and scratch coatings, etc required to build this, but am left wondering how or what if any do I use for a air gap between the wall (plywood cladding) and the stone veneer?

Thank you.

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Replies

  1. KEVIN ZORSKI | | #1

    I. Wilson - Ideally you would have an air space between the back of the stone and the sheathing, much like a brick veneer would use. There are commercial products for this. That being said, I have built 2x6 walls with 2"of foam over them and 8-10" of stone applied right to the foam( I used a slip form where the back of the form was the fixed foam sheathing and the front of the form slipped up as I built the wall from fieldstone.) That wall has held up well(10 years old now), but I'd put an air space if I did it again with weep holes at the bottom.There is a potential problem, especially on the south side of solar driven moisture, as the stone would be considered a "reservoir" cladding. Martin and Lstiburek have both written articles on this.It sounds like you would be building a veneer of stone, 4" ? , which would allow even more wind driven rain to enter. If so, just follow the guidelines for brick veneer which there is plenty of information about. Read about : 1. air spaces behind brick veneers, and 2. Resorvoir cladding and solar driven moisture.One good and quick read is"Best Practices:Methods for Installing Brick or Stone Veneer",by Matt Risinger. Good luck on your project.

  2. GBA Editor
    Martin Holladay | | #2

    I. Wilson,
    Ideally, you need at least two layers of asphalt felt (or a similar WRB) as well as a three-dimensional plastic mesh for drainage.

    For more information on three-dimensional plastic mesh products, see All About Rainscreens.

    Here are some links to products you might consider:

    http://www.stucoflex.com/rainscreen_drainage_mats.htm

    http://www.mtidry.com/products/product.php?Prod_ID=PCC2416,%20PCC2432

    http://www.cosella-dorken.com/bvf-ca-en/products/rainscreen/products/dry.php

    This type of wall assembly is fairly risky, especially if the drainage details and water-management details (including flashing) aren't impeccable. Don't skimp on the details if you want to keep your walls from rotting.

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