When someone mentions stucco in the realm of the real estate industry, oftentimes people get a little nervous and skeptical – and in many instances, rightfully so. There have been some terrible situations that people have encountered regarding stucco exteriors that were poorly installed and failed miserably, resulting in tens of thousands of dollars in repairs. So the raised eyebrows that you might get when you talk about an “EIFS” home in context with a real estate transaction may be frustrating, but there is some merit behind the skepticism.
However; what if I told you that stucco (including EIFS) is actually a really good exterior siding material? In many cases, it’s far better in terms of performance than a lot of other exterior cladding materials that we insist on using on our homes and buildings. I must be selling the stuff, right? … Actually, no. I just inspect it.
Here’s the first thing you should know. Stucco is not the enemy! The people who don’t understand how it works and who don’t understand how to install it are the enemy. Maybe not necessarily “the enemy”, but they are the ones responsible for writing the scarlet letter above the front door. Their lack of knowledge of the exterior envelope system and sub-standard installation methods is what has given stucco the bad reputation by not following the primary principle of exterior cladding installation: Move water down, out, and away.
As a prerequisite, let’s understand that basic foundational principle:
We must move water down, out, and away.
Water will land on and around our structures. It’s impossible to avoid. How we manage the water that lands on and around our structures will either save us from massive failure with the building components, or it will let us ride the wave (pun intended) straight to our pending doom.
From the top of the structure to the bottom, we need to manage the water and move it away as quickly and efficiently as possible. When it lands on our roof, move it to the gutters. Once in the gutters, let’s move it through spouts to the ground level. Once at ground level, let’s move it away from the foundation and send it on its way.
Here’s the thing we need to understand about siding (also known as “cladding”); the same principle applies. Move water down and away as fast and efficiently as possible. Water that touches the sides of the structure is attempted to be shed away on the surface if at all possible. If we can let it run down the surface and send it away from the foundation by grading the soil positively away from the foundation, then we’re all set. But we have learned that it’s not that easy. Not only is water flow difficult to control; there are other ways that it can move in and around our wall assemblies that make it impossible to achieve a complete exterior barrier on the surface.
This is why we now use weather-resistive building wrap on our homes. We know that we cannot keep water completely on the surface of our exterior walls, so in reaction, we now require a barrier below the surface that will help to shed incidental water that finds its way behind the surface. We do everything we can to keep it out, but just in case something gets by our first layer, we’ve got a backup plan. If water gets through or around the siding then we have a barrier below the surface that will move water down (around windows and penetrations) and back out to the surface – then down and away from the structure.
Now with that basic principle and understanding in mind, let’s talk about stucco. In hopes of not getting too far down in the weeds with technicalities and lullabies that will put you to sleep, I will keep this very basic and broad – speaking mostly in generalities. We’ll talk about the two main types and what you need to know with each.
EIFS (Exterior Insulation Finishing System) aka “Synthetic Stucco”
This type of wall assembly consists of (from the inside to the outside): a substrate material (most of the time this will be wood-framed walls with plywood or OSB sheathing), building wrap, foam insulation panel, mortar base coat with fiberglass mesh, and finish coat.
When EIFS was first installed, the goal was to assemble a “barrier system”, which meant that we were attempting to keep water completely out of the wall assembly. Fully seal the surface so nothing can get in. In theory, the concept seems logical and it can work if we can accomplish that one main objective (to keep water out). The problem is that it was installed so poorly that it let excessive amounts of water leak behind the surface resulting in catastrophic damage to the wood frame wall assembly.
In short (and again, very generally speaking), no one put this stuff on correctly and it caused many homeowners tens of thousands of dollars in damage. Water leaked behind the walls without any indication until the entire wall cavity was riddled with water damage, mold, and all kinds of fun treasures to await the unsuspecting victims.
This is where “stucco” gets a bad reputation. This is also why more recent building standards have evolved to accommodate the potential for water entry into wall assemblies. We understand that it is near impossible to keep water out, so we now require building wrap and drainage planes below the surface of our cladding materials so that “just in case” some water finds it’s way in, we move it back out.
Newer EIFS systems are required to be installed with drainage systems below the surface. This can be as simple as building wrap or as complex as more sophisticated drainage systems installed specifically for EIFS systems. We try to keep it on the surface, but just in case we don’t get it perfect, we’ve got back-stops in place to capture it and move it back out – preventing damage to the building components.
So when looking at an EIFS system, it is important to understand whether you are looking at a “barrier system” or “drainage system”. Understanding the two types of systems will help to ensure that the entire cladding system is installed and functioning as it is intended to do – rather than allowing moisture an opportunity to find it’s way below the surface – preparing us for a nice little surprise down the road.
The other type of stucco is known as “hard-coat”.
Again, I will speak very broadly and generalize this type of system. A typical installation from the inside of the wall to the out: wood-frame structure with plywood or OSB sheathing, two layers of building wrap, metal lath, mortar base coat and finish coat (ideally around 1 inch thick).
Hard-coat stucco is thought to have fewer problems than EIFS; but in all reality, it’s installation requirements are very similar and it can have the exact same issues (water damage below the surface). The only thing that is really different is some of the products that are being used and some of the methods of assembly (EIFS utilizes foam insulation boards while hard-coat relies on a thick mortar application). Outside of that, we are still looking at a masonry siding that is mechanically attached to the framed wall. Keeping the water moving away from the surface is still a top priority, but there are back-up systems below the surface to handle the incidental moisture entry that is likely to occur.
Regardless of whether we are looking at a hard-coat or an EIFS application, the primary principle in today’s building standards are the same: Try to keep water moving down, out, and away; but just in case we are imperfect (which is typically the case), we have a back-up plan in place to capture incidental moisture and move it back out of the wall and away from the building materials.
That’s kind of like life, eh? We try to be perfect but typically fall short so we have to put back-stops in place to make sure we don’t screw things up. But I guess that’s another conversation for another day. For now, I’m just sticking to what I know – and I hope it’s helped shed some light on a commonly misunderstood view of stucco cladding systems.
Feel free to drop me a message if I can ever be of assistance.
Godspeed, my friends.
Exterior Design Institute Certified Exterior Cladding Inspector