This article is outlined to provide detailed technical information and procedures regarding stucco remediation, EIFS remediation, window flashing with stucco and EIFS, and the building envelope as a whole.
By definition, cladding is the application of one material over another to provide a skin or layer intended to control the infiltration of weather elements, or for aesthetic purposes. It is best to design and install a cladding that can manage and control water infiltration. Nobody should rely on caulks and sealants because over time, caulks and sealants always tend to fail from either movement, degradation from sunlight, or from temperature. Water is always bound to get behind the exterior cladding of a building. It doesn’t matter if its brick, vinyl siding, stucco, stone, or EIFS, water will find a way through it. If you install a drainage plane and flashing with this type of mentality, you will never have to worry about water coming into the building.
I. A weep screed is a vinyl or metal track acting as a flashing to allow for drainage at the bottom of the drainage plane. It is the starting point of every drainage plane. Drainage planes begin at the framing foundation junction, above roof lines, on top of decks, porches, and sidewalks. It provides an exit by allowing the moisture that is draining down the wall to escape away from the wall. Many people think that the holes in the weep screed are weep holes to allow for moisture to drain out when in fact that is wrong. The edge, or lip, of the weep screed is what allows the moisture to drain out. After the cement and stucco are applied on top of the weep screed, the cement will shave away slightly on top of the drip edge of the weep screed and that becomes the exit for moisture. In the past, stucco has been furred off of the foundation by using wire lath to make it flush with the stucco that’s on the framing. This made the framing foundation junction invisible. Even though this may seem aesthetically pleasing, nobody knew that this was a big mistake in installing stucco. When moisture is traveling down the wall, it is looking for a way out, and when there’s no way out, it will get stuck at the junction and continue to look for a way out. What winds up happening is the moisture will wick back up the wall behind the building paper and may even start to rot the building paper and the sheathing. This may even cause people to get water on the sub-floors or in their basement because the moisture can travel inwards at the framing foundation junction. Sometimes people may even see termites inside their house as a result.
a. Drip caps and drip edges serve the same function as a weep screed. Drip caps get placed above all doors and windows. Drip edges are used to separate two different drainage planes of different materials such as stucco on top of a brick or stone water table.
II. There are three very important components to look for when it comes to the building paper. The first and most simple component is to see if the building paper was overlapped properly. Similar to shingles on a roof, every next sheet of building paper needs to get lapped on top of the sheet below it. The overlap should be at least four to six inches. The second component to check is to see if the building paper is a 60 minute Grade D building paper. The third and maybe the most important component to look for is whether or not there are two layers of the building paper. This is crucial when it comes to the drainage plane because the top layer is a sacrificial layer to the bottom layer. The top layer acts as a bond break to create an air space to allow moisture to travel down the bottom layer and out at the weep screed. We call it a bond break because the modern day building papers have been sticking to the back of the cement allowing for no air space. With no air space or means for drainage, moisture gets trapped against the sheathing and mold will start to grow.
a. There was a building paper called 15-pound felt paper that was asphalt based. It weighed 15 pounds per 100 square feet. In today’s modern day felt paper, the 15-pound felt paper weighs less than 7 pounds per 100 square feet. More than half of the cellulose and asphalt content were taken out of theses building papers. When the first coat of cement was being applied on top of the wire lath, the old heavy felt papers would absorb water from the cement and the paper would swell. As the paper dried, it shrank and de-bonded from the back of the cement creating a drainage space. The instability of the cellulose is why the bond between those older building papers and the cement did not occur.
III. The wire lath that is required in the stucco system is 2.5 gauge galvanized self-furring wire lath. For those of you who aren’t familiar with the term furring, furring is the process of building away from an existing wall using furring strips, or in this case wire lath, to support a finished surface, being the cement and stucco. The wire lath needs to be self-furring which means that it needs to be pushed away from the wall. The wire lath is self-furring by its dimples, or indents, in the lath itself. These dimples are created in the manufacturing process of the lath. It is very important that the wire lath is self-furred from the wall because the lath needs to get embedded in the cement when the cement is installed. This gives the stucco wall its strength and durability. In the past people have used flat wire lath with no dimples or indents. This means that when the cement is applied, it is more likely that the cement will just be hanging on the wire lath versus the lath being embedded in the cement.
a. Wire lath is installed with fasteners, whether its staples, nails, or screws. It is mandated that the fasteners only go into the framing members, hence the studs, no more than six inches apart from each other. In the past, fasteners have been placed all over the wall without any awareness of where the studs were. When the fasteners are shot into the sheathing and not the studs, it allows a direct route for moisture to run down the shaft of the fasteners to the inside of the wall cavity (in between the drywall and the sheathing).
b. When you have the shaft of the fastener exposed in the wall cavity, the shaft becomes a conductor of condensation. Condensation gets collected on the shaft by means of thermal bridging in the wall cavity. Thermal bridging is what happens when you have a cold glass of water outside on a hot summer day. It starts to condensate on the outside of the glass. This happens not because the glass permeable and leaking water, it’s because of thermal bridging. Not only on a stucco wall, but any exterior cladding, thermal bridging can cause condensation on the shaft of the fastener. The fastener being in the studs becomes insulated from the wood so no condensation can accumulate from thermal bridging. When there are a lot of fasteners in a smaller area, the fasteners are squeezing the wire and building paper tighter to the sheathing which can cause moisture to get trapped in those areas.
IV. Stop beads, or casing beads, are used wherever the stucco meets a dissimilar surface such as sides of windows and doors, soffits, fascia, vinyl siding, and trim. The end of a stop bead gets placed about a half inch away from the dissimilar surface to provide a joint to receive backer rod and caulk. The sole purpose of these joints filled with backer rod and caulk is to control for differential expansion of dissimilar materials. The common misconception is that stucco needs to be caulked everywhere it meets a dissimilar surface (mainly windows). You should never have to caulk your windows where the stucco meets the window anyway because if the window flashing was installed properly with the drainage plane of the stucco, you will never have a problem if the concern is about water infiltration. A lot of houses with stucco already on them may not have stop beads or caulk around the windows or dissimilar surfaces and home inspectors always say that windows, doors, and light fixtures need to be caulked where the stucco meets them. Unless these dissimilar surfaces have a stop bead allowing for a caulk joint, caulking where stucco meets a dissimilar surface would be ineffective. You cannot caulk to stucco or cement because water absorbs through the stucco and cement and will get behind the caulk.
V. Kick-Outs need to be installed at inside corners where the roof meets the wall. Rain travels down the valley of the roof and pounds that inside corner flooding the stucco wall. A kick-out gets tucked behind the building paper of the stucco and underneath the step flashing of the roof. The kick-out protrudes out of the stucco and diverts all of the rain into the gutter or away from the wall.
VI. Older mixes of cement and stucco had more lime making it more vapor permeable. As these products became more synthetic (adding acrylics, silicone, and polymers), they also became less vapor permeable which means they take longer to dry than a product that is more vapor permeable. Vapor permeability is simply vapor transmission, the ability to breathe.
VII. OSB vs. When plywood is much more vapor permeable when it becomes wet than when OSB (oriented strand board) becomes wet. Also, when plywood becomes wet, the moisture can move laterally whereas when OSB becomes wet it stays concentrated in that area.
VIII. Windows always leak. If they don’t leak right away from out of the factory, then they will leak at some point in the future. The rough opening needs to be treated with flashing. Particularly with a pan flashing at the bottom of the rough opening. This pan flashing is designed in a way so that not if, but when the window leaks, the flashing of the window will direct the water to drain out and on top of the drainage plane of the exterior cladding. If the windows are not flashed properly with the drainage plane on the exterior, it won’t matter if you have siding, brick, stucco, or stone, the windows will leak to the inside of the building and behind the drainage plane on the exterior.