Keep Weep Screeds Clear
By Scott Cohen
Over the years, many of the mistakes I've seen that result in the most severe consequences can be remedied by very simple fixes. Indeed, the simplest and best "fix" is to avoid making these mistakes in the first place. One example I've observed time and again has involved weep screeds.
The Scenario:
This one begins with a simple explanation of what weep screeds are and why they're used. When you have a home built on a concrete slab and the framing is bolted to that slab, the builder will put up some type of a waterproof material, usually tarpaper. On top of that, he or she will install a metal lath (wire mesh) over which stucco will be applied in three coats to achieve a thickness of seven-eighths of an inch.
In this case, the weep screed is above the deck only on the left side. To the right, it had been buried; as a result, mold grew undetected for three years before paint started to peel away inside the house.
We know that stucco is not waterproof. Water penetrates the stucco, hits the waterproof membrane (that is, the tarpaper) and then flows by gravity down to the bottom of the wall. At the bottom is a metal guide, the weep screed, which acts as both a guide for stucco application and, because it's perforated, allows moisture to escape rather than accumulate at the base of the wall. As a rule, weep screeds need two inches of clearance above a solid surface and four inches above soil — distances that reduce insect damage and water penetration.
In one scenario I inspected, a swimming pool had been installed two inches above the level called out in the design. Thus, the decking was two inches higher and as a result covered the weep screed back at the house.
No one discovered this problem until three years later, when the homeowners were selling the house and an inspection revealed toxic mold in the wall along the side of the house where the pool deck came into contact with the house. Because the weep screed had been covered, water had accumulated and caused a severe mold problem. Remediation involved hiring a mold-removal company to come and pretty much tearing down an entire side of the house — at a cost of about $150,000.
As shown here, stucco and drywall had to be removed in order to install a new, higher weep screed that accommodated the decking contractor's error.
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Scott Cohen is president and supervising designer of The Green Scene, an outdoor design and construction firm based in Northridge, CA. He provides consultation for clients nationwide and gives seminars on designing landscapes, swimming pools and outdoor kitchens.