I encounter many scenarios where the stucco is finished and then concrete is poured around the house and sometimes the finished height of the concrete seemed to be an afterthought and it is poured right up against the stucco walls, oftentimes burying the weep screed at the bottom.
This is a common occurrence, but is it acceptable? The short answer is that this is not the "proper way" to do it, but there doesn't seem to be a residential code that restricts it either, at the time of me writing this. I have experienced a lot of instances where this is common.
What Happens When Concrete Gets Poured Right Up Against The Stucco...
Stucco protects the wall from moisture and when done properly, has a water resistive barrier, usually in the form of a tar paper of some sort (2 layers) a base coat or a couple of base coats and then your finish coat(s).
This system is actually designed to breathe where moisture coming in will evaporate and wick down past the holes in the weep screed, if need be. When you pour concrete right against stucco, it adds an extra amount of water that will be absorbed by the stucco, especially if it is a larger concrete pad and will make it harder for the stucco to evaporate any water that has accumulated inside of it due to no air flow and the added moisture content from the concrete itself.
Something to keep in mind, is the fact that behind stucco is usually wood of some sort which includes the framing and oftentimes includes the shear wall as well, which can be OSB or plywood. This is usually where the problems can come into play when you pour concrete right up against a stucco wall. This usually doesn't happen until later down the road, though.
The Best Way To Do It...
The absolute best way to pour concrete with stucco walls would be to know what your finished concrete heights are and then maintain a 2" gap from the top of the concrete to the bottom of the weep screed edge.
This will provide the best chance of eliminating water intrusion from potentially happening.
Another Alternative Way...
If there is a situation that arises, where the concrete has to be poured above the weep screed and up against the stucco, you could always determine the finished height of the concrete and snap a line on the stucco, then break out the stucco 8 inches higher than that to allow for weep screed to be added.
I would also recommend adding additional flashing in that area to compensate for the extra moisture that can potentially affect the area that will be covered by concrete to eliminate any possibilities of moisture intrusion down the road. This can be achieved by using a rolled metal flashing material that would be installed on the shear or framing (open stud) before the weep screed is installed.
You will still want to maintain that 2 inches above that finished height of the concrete though.
Other Things Worth Mentioning...
There are a couple of other things that are worth mentioning that I didn't go into in the article, but I did want to touch on them, just in case some of you out there were wondering.
If you happen to be one of those people who have already had a project done where the concrete was poured up against the stucco, then I wouldn't worry too much about it at this point. It would be a lot of work to tear out the concrete and add flashing behind the wall, so I would just leave it if there are no current problems.
Another thing I wanted to mention was that if the area where your concrete will be poured up to the stucco is covered, meaning there is a roof over head that would protect against the elements, then you have even less to worry about (in most cases).
I still recommend the two methods I outlined in this article, but the chances of potential water intrusion are greatly reduced compared to an area that had no covering whatsoever.
