The quick, easy answer is absolutely, yes! The follow-up question is more important – why should you care and how does it affect your home?
Getting back to the easy answer – in simplest terms if the appearance of something changes when it gets wet, such as brick or stucco getting darker – that means it has absorbed some water. If it can absorb it, the water can potentially migrate through the material to the other side. That other side is inside your wall system and the water can cause some serious damage if not handled properly. Brick, stucco and siding (other than vinyl or aluminum) are technically referred to as “reservoir cladding” systems due to their ability to absorb, store and discharge water in varying degrees. The discharge aspect is what must be properly addressed. Discharged to the outside, no problem. Discharged to the inside, potential for mildew, mold or rot.
All these cladding systems require a water management system behind them – what is referred to as a “drain plane”. That is a water resistive (generally not waterproof, more on that elsewhere) material that stops the movement of moisture further into the wall system and directs it back to the outside. House wrap, building wrap, Tyvek – these are all examples of a water resistive barrier, or WRB for easy reference. Virtually all new homes incorporate a WRB somewhere within the wall system to manage the movement of moisture into the home. It is not only there to keep rainwater from getting into the home, but to deal with humidity in our homes as well. In the deep south our air conditioners work equally hard to lower the humidity as to cool the air inside our homes. That process reduces the humidity, temperature, and pressure inside the home, which mother nature hates (she really wants everything the same, everywhere). So now we have mother nature trying very hard to force her high humidity (read water in the air) into our homes. That is why a WRB is necessary in our current air-conditioned environment. Not so important in our grandparent’s houses before air conditioning. This is just one of the many, many huge differences in homes built today as compared to 100 years ago.