Rainscreens are great and really help to improve the entire way that the different stucco systems work and some people wonder if weep screed is even needed, since the rainscreen is more efficient at handling interior moisture.
Why would I need a piece of metal at the bottom of the wall that wicks moisture out? Let's take a look at the details to find the answer.
Do I Need Weep Screed If I Am Using A Rainscreen?
The answer is yes, weep screed still needs to be installed at the bottom of the walls even when a rainscreen is being used. It is still a required part of the stucco system, as a whole and building codes still require it.
Does A Rainscreen Replace A Weep Screed?
The answer is no, a rainscreen will not replace weep screed because it does not function the same way or do the same thing.
A rainscreen just provides an air gap behind the stucco to allow the system to dry out if any moisture gets trapped behind it.
The weep screed allows excess moisture within the wall to weep out of the holes that run along the bottom of it (weep) and also allows air flow in the wall, via those same holes, with the added benefit of providing a depth gauge (screed) for the layers of material as well.
Weep Screed & Rainscreen Thicknesses
You will, however, need to be sure you have an appropriate sized weep screed when planning on using a rainscreen because the rainscreen itself has it's own thickness that can add to the total thickness of the stucco system.
For instance, a typical three coat stucco system will consist of paper, wire, a scratch coat, brown coat and a finish coat or coats. That is typically specified at a total overall depth of around 7/8 inches.
If you were to add a rainscreen to that assembly that was 1/2" thick, that would only leave you with 3/8 of an inch left to work with, which would not be adequate for a three coat stucco system with a standard 7/8" weep screed. You would need to go with a 1 3/8" weep screed instead to give you those thicker base coat layers.
Weep screed comes in varying sizes (thicknesses) but these are limited by the manufacturer and do not increase at specified intervals. The below image is a screenshot from Stockton Products, which is one supplier of weep screed and they specify thickness ranges from 1/2" all the way up to 1 1/2".
With that said, rainscreens usually come in many different widths as well, to better suit your needs. Take a look at Stucoflex's website as an example of the different size rainscreen thicknesses. With that said, making adjustments between the thickness of the rainscreen and the weep screed will usually be necessary.
