Did you see my post a few weeks ago about a massive stucco failure? Stucco and it’s failures seems to be a perennial hot topic amongst builders, architects, and even realtors! I saw yesterday that it made the Builder Magazine top 5 list of dreaded callbacks.
So, how can we build a stucco assembly that will be just as durable and “safe” as a traditional siding house? First, we must understand that stucco is a Reservoir cladding. I’m quoting Building Science Corp on this cladding since I can’t say it any better….
“Claddings made of wood, fiber cement, stucco, concrete, and masonry all absorb water to varying degrees. Once the reservoirs get wet, the stored water can migrate elsewhere and cause problems. Therefore, reservoir claddings must be decoupled from water sensitive materials of the wall assembly.
As with any cladding in a water-managed assembly, drainage must be provided behind reservoir claddings. Drainage requires two things: 1) a drainage plane and 2) a drainage space (see Information Sheet 301 – Drainage Plane/Water Resistive Barirer).
Absorbed water migrates by capillary transport or changes to a vapor and migrates by air flow or diffusion. Therefore, in addition to drainage, reservoir claddings also require control layers for capillary water, airflow, and water vapor. ” - Building Science Corp – Reservoir Cladding Info Sheet Link to read the whole article
The quote above refers to both a “Drainage Plane”, and a “Drainage Space”. The Drainage Plane is basically the WRB or the waterproofing you see on the outside of the structure, but here’s where Delta Dry Stucco & Stone comes in as it provides a unique (and easy) method to provide that drainage space (often referred to as a Rain Screen).
Delta Dry Stucco & Stone comes in rolls that look alot like a foundation waterproofing product. It’s a plastic dimple mat on the back…
You can see the plastic dimple has a fabric adhered to one side. The plastic nipples go against your WRB (weather resistive barrier) and the fabric faces out.
It’s hard to get a good close up on the fabric, but it look alot like a silt fence material. Obviously porous and lightweight but tough.
It rolls out easily as it’s lightweight and we tacked it up with a few roofing nails. What I really like about this product is that it creates two air spaces that are separated by the zero perm plastic dimples. Once you roll this on, you’ll have an air space in front of your WRB (Delta Vent SA on this house I built) AND you’ll have another air gap behind your stucco. This is really unique because now when my stucco gets wet and absorbs water it can dry in the air gap behind without getting the air plane in front of the WRB steamy. I’m referring specifically to Solar Driven moisture. This happens alot in the South: Sprinklers go off at 4AM and wet the stucco 3x per week but when you get out of the house at 8Am the stucco appears dry but it’s actually full of moisture. Then, the Sun comes up and hits the house at 11AM. That moisture in the stucco is driven by the solar radiation to want to dry towards the inside. This is why your air barrier & vapor barrier is so vital on the outside of your house. If there are any penetrations in your WRB that leak some air that air is going to be very moist/humid and when it leaks inside the wall cavity it will drop that moisture once it hits a cold condensing surface. Mold and Rot occur and sometimes it’s a dramatic failure, sometimes it takes a decade+ to show up. See this photo below of a 10 year old restaurant that had stucco getting wet from a sprinkler head.
Sorry for the Building Science tangent… once the Delta Dry Stucco & Stone is applied you’ll staple the wire mesh up as usual but with a longer staple. Also, you’ll notice that we are NOT using a layer of felt behind the stucco. The felt behind stucco is meant to be a bond breaker, meaning the stucco scratch coat (1st coat) bonds to the felt paper and the WRB behind that won’t get clogged. In this case, the fabric on the Delta Dry Stucco & Stone is the bond breaker and keeps the scratch coat from filling the air space.
The rest of the Stucco job proceeds as normal. This project was a traditional 3 coat system with the finish coat being an integral color LaHabra Smooth Santa Barbara Mission Finish.
That smooth stucco looks fantastic when it’s all done! Notice my custom hood for the electrical panel, I need to do a blog post on those too. Also, the AC Linesets have my favorite QuickFlash flashing boot on them.
I took these pictures after a rain event and it’s pretty clear how the stucco is absorbing water! I’m glad I’ve got a nice air gap behind there so it can dry harmlessly!
If you’d like more info on the Delta Vent SA housewrap you can see my review here. And here’s the link to the Delta Dry Stucco & Stone homepage.
I’ll leave you with a Dr Joe Lstiburek quote:
“Rain is the single most important factor to control in order to construct a durable structure.”
- Risinger Homes in Austin, TX
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Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.
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