There are two basic ways of making this change. One is not replacing the EIFS per se, and the other is. The former method is to apply stucco over the EIFS, leaving the EIFS in place. The latter is removing the stucco and replacing it with EIFS.
If you want to put stucco over the top of an existing EIFS there are several things to consider. The nice thing about this approach is that it bypasses the messy demolition process, allowing completion of the work more quickly, with less annoyance to the building's occupants, while maintaining the energy efficiency provided by the EIFS.
Bury my EIFS at Wounded Knee
One of the main reasons for removing an EIFS is that there is a problem with the supporting wall-in other words, to get inside the wall from outside the building. The problem may be something in the wall cavity, such as rotted wood framing. Putting stucco over the EIFS simply buries the problem, perhaps leaving the wall to its own unpredictable future. Obviously to get at the guts of the wall, the existing EIFS has to be removed. Often, problems with the existing wall are limited to one or more small areas, usually near an opening. This means that fixing the damaged area requires only taking off a section of the EIFS, which can then be replaced and the new stucco then installed over it.If the existing EIFS has joints in it, there will need to be a joint at such locations in the new stucco. By this I mean a real, working, expansion-type joint, not simply an aesthetic reveal.
One of the things that make EIFS attractive to designers is the ability to do large areas with no joints. If you put stucco over EIFS you will need to put control joints in the stucco in the traditional manner. This can dramatically change the appearance of the façade and needs to be thought through beforehand to make sure it looks good.
When attaching the building paper and lath over the existing EIFS, one will want to fasten through the EIFS and into the substrate. This can sometimes be a problem if the sheathing is a gypsum-based product, since nail or screws will not hold in the gypsum. This means figuring out where the studs are, which can be a pain in the neck, especially if the EIFS foam insulation is thick. One should not want to try to attach into the EIFS lamina, as it not strong enough to handle the weight or resist wind pull-off forces.
If there are foam shapes on the surface of the EIFS, one may have to remove them and replace them with new ones. In other words, it's often easier to start with a flat EIFS surface than trying to build up stucco over an existing EIFS foam shape.
Obviously, adding stucco over EIFS changes the thickness of the cladding, and the perimeter needs to be checked of the new stucco to see if it fits properly and looks OK where it comes up against other wall components. It's not unusual to have clearance problems at doors and windows, making it difficult or impossible to open or close the window or door.
Clearly, EIFS finishes can be used as the top coat for the new stucco, which can help retain the original look of the wall, i.e., the same color and texture. The same sort of problem can occur where a flashing laps over the top of the existing EIFS. A new flashing or an extension piece to the existing flashing may be needed to make a good seal.
When applying stucco over EIFS, one thing you do not want to try to do is to apply stucco directly onto the EIFS finish without using lath. Even if the scratch coat appears to be sticking to the EIFS, it will eventually work its way loose. Stucco is inorganic and EIFS is organic, and the two materials move at different rates, creating a plane where they meet that is unstable. This adhesion problem is even more pronounced with some of the newer EIFS finishes that contain chemicals to make them more hydrophobic (water shedding), which makes attaining a good bond even more difficult.
Another thing to avoid is leaving out the building paper. The paper acts as a water barrier, obviously but also makes the stucco "detach" from the surface it is adjacent to, allowing the stucco membrane to move independently from the supporting surface, thus reducing the tendency to crack.
Removing an existing EIFS has its own set of issues. One of the most important is the condition of the substrate, namely, will the substrate be damaged during the removal process? The answer is yes, at least to some extent. This is particularly true with EIFS foam that is glued to gypsum substrates, where yanking off the foam can gouge of break the sheathing.
The adhesive from an adhesively attached EIFS will stay on the substrate after the foam has been ripped off, making it no longer flat. The "can-sometimes" affects the ability to lay the building paper and lath flat against the substrate.
Remove with caution
If you are removing an EPS-based EIFS, be careful about the EPS beads. They can end up all over the neighborhood, even in the slightest breeze, resulting in annoyed building owners and clean-up hassles.Because even the thickest stucco will be thinner than the thinnest EIFS, look carefully at the perimeter of the new stucco to see how it fits together at openings and at flashings. For instance, windows that were originally recessed into a thick EIFS layer may now project out past the new stucco, requiring new flashing.
Stucco is more brittle than EIFS and requires a stiffer supporting wall to avoid cracking. Usually, this is not a problem but the applicator may have "springy" framing that deflects a lot. The use of very light gauge steel studs is a common source of this problem and this deflection issue can easily be checked by a structural engineer.
One of the more serious issues that can occur when removing and replacing an existing EIFS with stucco is the loss of insulation. Often, the EIFS contributes significantly to the overall R-value of the wall and removing the EIFS insulation can dramatically increase the energy usage of the building. One way around this is to apply a thin layer of foam insulation over the sheathing and attaching the lath and building paper through it. This, in effect, is like reapplying a sort of stucco-based EIFS but at least does address the loss-of-insulation issue.
Regardless of whether or not you clad over the EIFS with stucco or remove and replace the EIFS with stucco, one will want to do a complete survey of the existing wall to see what things need to be worked around or replaced. So of the thornier "in-the-way" objects are fire escapes, electrical signs and tie-downs for window washing equipment.
Although it is often not an issue, the fact that stucco weighs much more than EIFS can sometimes be a problem. EIFS weighs about 1-pound per square foot, making it one of the lightest claddings. Sometimes, buildings have weight issues, such as those on pilings (such as on a boat dock) or tall buildings where the weight accumulates from floor to floor. The same issue applies but even more so if one tries to replace EIFS with brick. With brick, the brick itself needs to be on a firm support and does not "hang" off the framing the way stucco and EIFS do. This issue shows up mostly at the bottom edge of walls, at the foundations and at window heads.
Although stucco is more fire resistant than EIFS, check and see what effect-if any-of changing the wall's construction has on the fire rating of the wall. This is a building code issue and may be a factor, for instance, when buildings are close together in densely populated areas.
Replacing EIFS with stucco has the nice advantage that one can attach some objects directly to stucco. The thinness of the EIFS lamina makes it impossible to attach most things to it. With stucco, lightweight, nonstructural objects, such as numbers and letters, can be attached to the stucco without going through to the substrate.
The whole idea of replacing EIFS with stucco is a bit of an odd exercise in the sense that usually is only contemplated when there are some sorts of dire circumstances, such a damaged supporting wall or a fire, or some fundamental product-use hang up, such as insurance or building valuation problems. Usually, if the EIFS or its supporting wall needs to be repaired, one can do so only where the problems are and leave the rest of the wall as-is, saving time and money.
