cracks in EIFS siding

Synthetic Stucco

EIFS History

EIFS Layers

Exterior insulation and finishing system (EIFS) is a type of building exterior wall cladding system that provides exterior walls with an insulated finished surface and waterproofing in an integrated composite material system. EIFS was developed in post-World War II Germany to repair war-ravaged structures as well as address the energy consumption caused by lack of insulation in masonry structures.

Although often called “synthetic stucco”, EIFS is not stucco. Traditional stucco, otherwise known as Portland Cement Plaster, is a centuries-old non-insulating material. EIFS is a lightweight synthetic wall cladding that includes foam plastic insulation and thin synthetic coatings. There are also specialty stuccos that use synthetic materials but no insulation, and these are also not EIFS either. A common example is what is called one-coat stucco, which is a thick, synthetic stucco applied in a single layer (traditional stucco is applied in 3 layers). There is also an EIFS-like product called a direct-applied finish system (or DAFS), which is essentially an EIFS but without the insulation, and has quite different characteristics

Insulating a building traditionally takes place by placing an insulating material into the wall cavity. It was discovered that insulating a building from the outside would be more energy efficient, since insulating from the inside leaves thermal breaks in the insulation where the wall stud exists.

Wood framed homes have a wall cavity between the drywall and exterior siding. These homes reduce their energy costs by filling the wall cavity with insulation. When EIFS was developed, it made insulating a building from the outside possible by attaching sheets of foam insulation over the entire exterior, thus eliminating any thermal breaks. This allowed Europeans to reduce their energy consumption as well as beautify their homes.

Dryvit Systems, Inc. introduced EIFS into the United States in 1969. With the onset of the energy crisis during the early 1970s, EIFS became popular among energy-conscientious architects and builders. During the energy crisis, many U.S. and European manufacturers entered the EIFS market place.

EIFS was first introduced to the commercial market-high-rise condominiums, office buildings and stores were the first buildings clad with EIFS. It was not widely used in residential construction until the mid-1980s.

EIFS manufacturers began marketing EIFS to the residential market in conjunction with the increase in housing starts that began in the mid-1980s. Touting energy efficiency, design flexibility and curb appeal, EIFS manufacturers successfully marketed their product line to high-end builders. During the 1980s, EIFS became a cladding of choice for many higher-priced residential homes.

What’s The Difference Between EIFS and Traditional Stucco?

Materials traditional hard-coat stucco exterior system is extremely strong and durable because it essentially covers your home with a layer of rock. Cement stucco is made of sand, a small quantity of lime, Portland cement and water. Basically, it is a fine-grained concrete that is attached to your house using a waterproof barrier paper, galvanized wire mesh and metal flashings (devices that channel water to the exterior of a wall). The stucco’s facade is meant to be a primary barrier, but a secondary or “concealed” barrier directs any water that gets behind the facade to the exterior. This creates a dual barrier to wind-driven rain, snow and ice. Barrier EIFS on the other hand, uses a multi-layer “synthetic” stucco that is much softer than traditional stucco.
“Breathability” while it has the appearance of stucco and is installed similarly, EIFS has some very different properties. One of the most important differences is that barrier EIFS will not allow water to pass back through its coating in vapor form once moisture gets behind the system. By contrast, traditional stucco is a porous material, which will permit moisture to move both in and out of the wall cavity.
Installation Barrier EIFS is comprised of a base coat and finish coat applied over an EPS board that is attached directly to the sheathing using fasteners or an adhesive. The system
provides no avenue for water to drain out once it penetrates behind the EPS board. Traditional stucco, on the other hand, is applied over a wire mesh, and installed with standoffs that allow space behind the stucco for “weeping” of water. No EPS or Styrofoam board is used in a traditional stucco exterior.

How can you tell what’s installed…..

There are a few simple tests that can be perform to determine whether the home has EIFS or traditional stucco.

“The Knock Test”  Sound or knock on an outer “stucco” wall of your home. If it sounds hollow, there is a good chance its EIFS or a hybred. If it sounds like a brick wall, it is more likely a traditional “hard-coat” stucco.

“The Gap Test”  Check the bottom edge of the cladding near the foundation, assuming that is possible (another common installation error occurs when the EIFS is installed below grade, making this test difficult if not impossible). If the siding comes out away from the foundation 3/4 of an inch or more, chances are its EIFS cladding. This is because the EPS board used in EIFS makes the system extend farther away from the wall than a traditional stucco system.

“Check Penetrations”   Inspect some of the penetrations in the stucco. Since most installers of EIFS do not create the proper joints around penetrations such as light fixtures, gutter straps, or doorbell/intercom devices, remove these items and check for the telltale foam board used in EIFS. If you see the Styrofoam-like board, you have EIFS. Traditional stucco exteriors do not use this element.

Still Not Sure? If you still are not sure what type of cladding you have, or you have any other questions, contact us at 360-588-6956

Discovery Of Problems

EIFS diagram

The problem with barrier-type EIFS cladding is that the systems rely entirely on their outside surface to prevent water penetration and moisture intrusion. Barrier EIFS have not internal drainage provision, and therefore require excellent design and workmanship to produce a weather-tight and long-lasting system. Throughout the United States, a significant percentage of homes clad with barrier-type EIFS are experiencing problems with water penetration and moisture intrusion, primarily around windows, doors, and roof-to-sidewall intersections where kick-out flashing is necessary. The retention of moisture in these systems for an extended period of time invariably leads to damage that frequently goes undetected for an extended period of time. In many homes clad with barrier EIFS, water that enters behind cladding does not evaporate, or “escape,” quickly enough to allow structural members to dry out. The moisture content and temperature inside the wall cavities of these homes often promote rapid growth of wood destroying fungus, leading to deterioration or rot of the sheathing/substrate. Depending on the size of the home, EIFS repairs can range from tens of thousands to over one hundred thousand dollars.

In contrast to residential construction, most high-rise condominiums, office buildings, and stores are made of concrete and steel. While problems with barrier-type EIFS have also been widely reported on these structures, such problems have generally taken a longer period of time to manifest then is the case with wood-framed residential construction.

Maintaining EIFS

General: In order for water to get into a wall, three things are needed: the water, an opening, and some force that cause the water to go through the opening. If all three of these items are not
present at once, then leaks will not occur. Since EIFS coatings themselves have no joints, it is best to look for leaks in areas other than the field of the EIFS wall.
Windows: Windows themselves, as discrete building elements, are a system of various materials, including the frame, glass, gaskets, hardware and other components. There are numerous
seams between these materials. These seams can provide the avenue for water entry. Some leaks open and close, while others are fixed (do not open or close). Operable windows tend to leak
more than fixed ones.

Expansion Joints

back rod for EIFS

One of the most visible EIFS flaws I see in Northern Washington is lack of expansion joints around windows and doors. Builders typically will run the stucco right up to the door or window frame.

The key to a trouble-free EIFS application is the maintenance of a 1/2- to 3/4-inch gap wherever EIFS meets a non-EIFS material, such as roofing, trim, or doors and windows. The correct gap makes it possible to finish the exposed edges of the expanded polystyrene — which should be backwrapped with reinforcing mesh before the EPS is secured to the sheathing — with a waterproofing application of base coat when the rest of the finish goes on. Finally, the gap is filled with soft plastic backer rod and a bead of compatible caulk.


EIFS Caulk being applies

Sealants, unlike some other types of sealing techniques, rely on developing a bond between the sealant and the adjacent material, such as a metal flashing or a window frame or concrete. Gaskets, in contrast, work by constantly being compressed against the adjacent surface. Compression, not adhesion, creates the seal. The fact that a sealant is in contact with the EIFS does not mean it is bonded to it. This fact can be seen most readily when the wall contracts when it gets cold outdoors and the sealant joint opens up; what previously appeared to be a well-bonded joint is now wide open. Hint: If you suspect that there are bond problems, do your forensic work on a cold day. On hot days, the joint gets compressed, and bond problems are harder to see.

The simple fact of the reliance by sealants on adhesion is the source of numerous sealant-related woes and has many implications.

To achieve adhesion, the sealant must stick to the adjacent material. No kidding. But it must stick tenaciously and permanently. When sealant joints get wider, usually due to the reduction of temperature and resultant contraction of the adjacent materials, the sealant bead becomes stretched because it is being yanked-on by the adjacent materials. This imparts a pulling force on the bond between the sealant and the adjacent materials. This tends to pull the sealant away from the adjacent material. Unless the sealant can remain bonded, the joint may open up, and water can then enter. Many factors affect adhesion and with EIFS there are some aspects of this matter that make EIFS joints different.

Joints have two sides. This may sound dumb but there is no such thing as a one-sided EIFS (or any other) sealant joint. At least one side of the joint is the EIFS and the other (if there is another non-EIFS side) is some other material. Many EIFS manufacturers and sealant producers recommend the use of a sealant primer, applied to the surface of the EIFS, prior to applying the sealant. The purpose of the primer is to fortify the surface of the EIFS, thereby improving the adhesion of the sealant, particular under damp conditions. This means that there may actually be two sealant primers in a single joint: one for the EIFS side of the joint and the other for other side. These primers may not be the same type of primer. It’s a good idea to check various sections of the projects specifications (if there are any specifications!), to see what other types of materials are adjacent to the EIFS. It’s quite possible that the non-EIFS materials may require a different primer, or may even need a different type of sealant.

A little recognized effect that can cause sealant adhesion problems is due to the thermal conductivity of the joint itself. Here’s what happens:

The EIFS portion of an EIFS-clad wall is essentially a solid, unbroken layer of insulation with a seamless layer of coatings on the outside. The breaks in the layer of insulation occur at the perimeter of the EIFS, notably at the EIFS sealant joints. Often in winter, the interior of the building has a higher relative humidity than the outdoors. Thus, the moisture indoors tries to work its way through the wall to reach equilibrium with the outdoor humidity. Unable to easily get through the EIFS insulation, the moisture looks for the next easiest route, and migrates throughout the wall system, usually in the wall cavity. The sealant joint, which is wide open on its inside and which is also uninsulated, allows moisture in the air to get all the way to the back side of the sealant bead before it can go no further.

Because the sealant bead is in contact with the outdoor air, its temperature is at roughly the same temperature as the outdoor air. This causes the moisture on the inside of the sealant joint cavity, when it reaches the inside of the sealant bead, to get colder. This can lead to condensation in the sealant joint. In essence, water is deposited on the edge of the EIFS at the sealant bead. EIFS materials tend to soften slightly when exposed to moisture. This can cause the bond of the sealant to the EIFS to loosen, allowing water from outdoors to get in. The solution: Stuff some insulation into the sealant joint cavity before caulking it shut. This will keep the cavity at a higher temperature, reducing condensation potential. Make sure to use insulation that will not absorb moisture, lest the insulation become a sponge for any water that does get into the joint.

On a similar vein, when sealant joints are horizontal, it’s a good idea to shape them so that water can drain away from the joint. Ledges on the lower portion of the joint, and V-shaped sealant returns, direct water to the sealant area, which can let water into the joint, should an opening develop in the joint area.

Installing Sealants

EIFS roof flashing

Tooling is standard practice when properly installing sealants. The term “tooling” means applying pressure to the outside face of the wet sealant bead, after the bead is in place. Tooling forces the sealant into more intimate contact with the EIFS.

Recessing the original sealant bead into the joint by a 1/2-inch or so is helpful. This allows a new sealant bead to be applied over the old one without having to remove the old one. It also allows the new bead not to stand out past the outside face of the wall. It’s an understatement to say that removing and replacing old sealant beads in EIFS joints can be really expensive, hence this simple technique can be a real long-term cost saver.

Sealant quality is important, and it’s smart to use the best quality sealant initially, so that the time span between sealant joint maintenance, which should be a regular scheduled maintenance item, is maximized. EIFS sealant joints are so fussy and expensive to remove and replace that you definitely want to do it as few times as possible during a building’s life. Sealant materials are one of those “you get what you pay for” materials. The better ones cost more, but given the tiny percentage of sealants’ initial cost in relation to the whole wall, why be cheap with such a critical wall component?

Finally, reliance on sealants alone to provide weatherproofing is simply not smart. If the stucco was not installed correctly to begin with then caulk will not help, in fact it may increase the amount and speed at which damage may occur. There are many ways to provide redundancy to weatherproofing, such as using sealants in combination with flashings, designing the geometry of the joint itself to inhibit water entry, and providing a safe route for water to leave the joint, should it get in.

Flashings: Flashings are thin, shaped building elements, usually made of metal, but also sometimes made of plastics and other materials. Their main function is to div ert water away from interfaces, thus preventing leaks. Flashings are often in the form of long pieces. These pieces have joints, corners and holes in them, and hence these interfaces within flashings are possible sources of leaks.

Water in Walls: That Doesn’t Come From the Wall: Buildings are composed of numerous construction elements, including roofs, decks and other exterior surfaces which can have water on them. Water often finds its way through the wall construction and surfaces far from its original source. Roof leaks are common leak source which often manifest themselves in the walls. Do not assume that water in a wall comes from the wall itself. Be methodical and look for all water sources.

Leaks That Are Not leaks: Not all water exists in a wall due to the entry of liquid water from the outside. Water can also be deposited by other means, including the condensation of liquid water from gaseous water vapor. This can lead to damp conditions in a wall that are assumed to be from water leaks, when in fact they are due to hygro-thermal conditions that result in water being deposited in the wall due to the moisture in the air.

Leaky EIFS Coatings: It is possible for the EIFS coatings themselves to leak, this is extremely are. Normally your time is much better spent looking elsewhere. Remember that the EIFS coatings are backed up by a layer of insulation, which is also water repellant. So even if the EIFS coatings leak, the chances of the water getting through the field of the EIFS is small


Exterior Insulating Finish System (EIFS) is causing great concern in the resale housing market today. EIFS (pronounced “Eefis”) has many benefits. It has an acrylic coating that finishes to look just like the old- time, heavyweight stucco used on houses for 50 years or more. If your buying a home with a stucco exterior we recommend that the evaluation start with the home inspector. The inspector will need to know that they are dealing with Stucco prior to the inspection, as they will have to spend more time examining the exterior. The inspector will do a visual inspection of the exterior, especially in the areas that would have high moisture content and will determine if an EIFS specialist should do an in-depth evaluations. The EIFS specialist should be certified with the Exterior Design Institute or AWCI.  In an EIFS evaluation a non-intrusive moisture scanner is used to identify areas of relatively high moisture content. In areas where the scanner indicates high moisture content a probe moisture meter is inserted to test for the moisture content of the substrate and to test for damage to the substrate. If the probe moisture meter indicates high moisture content, or a soft section of wall is found, it may be necessary or advisable to conduct an invasive inspection. This will involve removing sections of the EIFS to physically inspect the substrate or framing. Sometimes significant damage is discovered, which, if not repaired, could jeopardize the building’s structural integrity.Since the rot is taking place from inside of the wall out, it often goes unnoticed for months until it has done substantial damage. Repairs can cost $3,000 to $20,000 and even more.

The 12 most common reasons for water intrusion of the stucco include things like poor or missing flashings, improper caulking, poorly designed or installed window assemblies, etc. Many of the major relocation companies are refusing to buy a house clad with EIFS without a complete invasive moisture survey. Some insurance companies are refusing to insure an EIFS clad house without a moisture test. An invasive moisture test and survey of EIFS is not something that is part of a visual home inspection, and many of the problems would go undetected by a normal home inspection. This is a separate test entirely that requires sophisticated meters and equipment costing several thousand dollars.

What do you do if there’s a problem? The first step is to have your house thoroughly and accurately tested for moisture problems. You have to know what the problem is and where its at before you can ever hope to correct it. Information from the testing will provide you with the information that you need to make modifications and repairs which can remedy the problem.

EIFS Links