Frequently Asked Questions
If you own a stucco home you are aware of the low-maintenance, sound-insulating benefits of this beautiful exterior material. If you don’t, then we’re here to help you understand and appreciate why stucco has been the choice of builders for centuries! If you have a question, we want to help you understand and welcome your calls. We’re here to answer any of your questions – none are too simple or complicated – so call us and have a conversation with Blaine or Darren. Better yet, call and make an appointment and let us see your home or commercial project so we can answer your specific questions intelligently.
At Nurse Stucco, we strive to fully inform our customers, and encourage you to contact us to learn more about your stucco project as well as how to protect and beautify your home or commercial building with stucco.
- General Stucco FAQ
- Stucco Aesthetics FAQ
- Stucco Application FAQ
- Stucco Materials FAQ
- Stucco Performance FAQ
Reasonably priced, easy to maintain and aesthetically pleasing, stucco has been a popular siding choice for hundreds of years. With a variety of colors and textures to choose from, stucco works well with any home’s exterior. Stucco is a more durable finish and it is also more fire resistant than other types of finishes. Stucco requires less maintenance than other exterior finishes. You can expect a quieter home with a stucco exterior and a higher degree of energy efficiency due to its superior insulating qualities. Stucco provides moisture protection while also allowing your home to breathe. Finally, in long term cost analysis, a stucco home provides the highest return on investment for the owner.
Stucco siding has been used for centuries. The ancient Greeks and Romans painted wall frescoes onto fine-grained hard plaster surfaces made of gypsum, marble dust and glue. During the Renaissance, the Italians elaborated stucco techniques, which, in turn, spread throughout Europe. While stucco is not a new building material, the changes made to finishes can make it seem like something a homeowner has never seen before. A wide array of styles and colors to choose from as well as different application techniques make stucco modern, yet timeless.
While you can’t really list the service life of stucco in a specific number of years, properly applied and maintained stucco, is as more durable than other commonly used cladding material. Its hard surface resists abrasion, and stucco can take a lot of physical abuse. It stands up to all sorts of climates, from cold to hot and wet to dry. To give you an idea, stucco has been with us since the early Roman times, and some of those buildings are still around. Here in the US, many homes built with stucco in the mid to late 1800s and early 1900s have had very little maintenance and remain in good shape today. At Nurse Stucco we offer a 25 year warranty on our new stucco and restucco work.
Are plaster, stucco, and EIFS the same?
The answer requires a bit of an explanation. Plaster is the general term for material that is applied to a wall surface in a thin layer. Portland cement-based plaster is such a material that uses portland cement as the binder. It is sometimes called “traditional stucco.” Stucco is a somewhat colloquial term for portland cement plaster, and most people in the construction industry consider it to refer to an exterior, not interior, finish. Exterior insulation and finish system (EIFS) is sometimes (incorrectly) called “synthetic” stucco. To complicate matters, “plastering” is the verb that describes the action of applying any of these various materials to a wall surface.
Portland cement plaster is applied either by hand or machine to exterior and interior wall surfaces in two or three coats. It may be applied directly to a solid base such as masonry or concrete walls, or it can be applied to metal lath attached to frame construction, solid masonry, or concrete construction. Applied directly to concrete masonry, portland cement plaster provides a tough ½-inch thick facing that is integrally bonded to the masonry substrate. When applied to metal lath, three coats of plaster form a 7/8-inch total thickness. A vapor permeable, water-resistant building paper separates the plaster and lath from water-sensitive sheathing or framing. Portland cement plaster has high impact resistance and sheds water, but breathes, allowing water vapor to escape. It’s a proven system that works in all climates.
Exterior insulation finishing systems (EIFS) consist of a polymer-based laminate that is wet applied, usually in two coats, to rigid insulation board that is fastened to the wall with adhesive, mechanical fasteners, or both. Polymer based (PB) systems, sometimes known as thin coat, soft coat, or flexible finishes, are the most common. The basecoat for polymer based systems is usually 1/16-inch thick and finish coat thickness is typically no thicker than the maximum sand particle size in the finish coat.
Exterior insulation finishing systems experienced performance problems in the mid 1990s, including water leakage and low impact resistance. While the polymer based skin repels water very effectively, problems arise when moisture gets behind the skin—typically via window, door, or other penetrations—and is trapped inside the wall. Trapped moisture eventually rots insulation, sheathing, and wood framing. It also corrodes metal framing and metal attachments. There have been fewer problems with EIFS used over solid bases such as concrete or masonry because these substrates are very stable and are not subject to rot or corrosion.
Clearly, portland cement stucco should not be confused with the exterior insulation and finish systems. The systems may share similarities in application techniques or final appearance, but the systems perform differently in resisting weather, especially wet conditions.
What are appropriate sheathing materials for plaster construction?
Rigid sheathing materials are commonly used behind plaster finishes. They are directly attached to support studs then covered with building paper or other weather resistant barrier (WRB). Metal lath attached over the sheathing and into the supports carries the plaster. The weather resistant barrier is intended to resist water penetration, so the sheathing is protected from moisture. That means that many materials are suitable for this application, but the common ones remain plywood, oriented strand board (OSB), cement board, and exterior grade gypsum sheathing.
In the early 1910s, basic research on stucco systems looked at the then-current practice of using board lumber (not panels) as sheathing. These were commonly 6- to 8-inch wide boards attached to support studs at 45 degree angles. During that period, diagonal placement of the boards transitioned to horizontal placement, and was followed by a move to 4-by-8-foot panels.
Wooden lath, small, narrow boards (1/4-by-1 ½ inches), were also common at that time. Although it’s not exactly clear when metal lath was first used in plaster applications, it appears that both metal and wood lath were available at least as early as 1910. Both wood and metal lath were common substrates for plaster at least through the teen years of the 1900s.
It should also be noted that it is possible to place stucco over open frame construction. This is accomplished by stretching line wires between studs and adjusting the wire to support paper as the backup to plaster. The paper is supported by the wire creating the backstop for plaster as it is applied to create the wall face. Because this is not as rigid as a board, the open frame method can allow for more variation in the thickness of the plaster. In addition it is important to understand that the open frame must be adequately rigid to resist deformation due to wind or other forces—that often means bracing the frame. The stucco layer may not be considered as part of the stiffening system.
Common sheathing materials today come in 4-by-8-foot boards. These are readily available building materials of consistent quality and are easy to install over wood or steel frames. The boards assure a more uniform thickness of the plaster layer and add structural rigidity to the building frame. For a variety of reasons, then, the currently preferred practice in many regions is to use sheathing boards for frame construction. As noted above, sheets of plywood, oriented strand board (OSB), cement board, and exterior gypsum sheathing are the most common materials for independent veneer plaster applications.
What type of cements can be used to make stucco?
There are many types of hydraulic cements that can be used as a binder for stucco, or portland cement plaster. The cement standards used in the United States most often are from the American Society for Testing and Materials (ASTM).
A hydraulic cement is one that sets and hardens when mixed with water. Cement, along with sand and water, are the basic ingredients of a plaster mix.
The following materials are candidate binders for stucco:
- Portland Cement, ASTM C150
- Blended Cement, ASTM C595
- Hydraulic Cement, ASTM C1157
- Masonry Cement, ASTM C91
- Plastic Cement/Stucco Cement, ASTM C1328 (primarily available in the west and southwest United States)
Hydrated limes, either ASTM C206 Finishing Hydrated Lime or C207 Hydrated Lime for Masonry Purposes, are also used with portland cement to provide workability. Hydrated lime may be used with blended cement or hydraulic cement, too, but is not used with masonry cement, mortar cement, plastic, or stucco cement. Those materials already contain workability agents and the addition of lime is neither necessary nor allowed. If used with those materials, lime poses potential problems such as reduced strength or durability.
White cements are also available for use in stucco. They are generally specified under C150, C91, or C1328. Specifying white cement – sometimes white cements are blended with pigment in the factory or on the job to create colored mixes. Where white or colored plaster mixes are used, they often are applied only as the finish coat.
Standards for all of these materials are available from ASTM.
Where can I buy stucco?
You don’t really “buy” stucco so much as you buy the materials to mix stucco onsite or hire a contractor to do the work. You can purchase materials to make stucco throughout the country at material supply houses and home improvement centers.
There are a variety of acceptable mixture proportions for stucco, and the proportions of each successive coat vary. The individual materials may include portland, masonry, or plastic cement, lime or other plasticizers, sand, and water.
The following documents contain tables of mixture proportioning recommendations:
- Portland Cement Plaster/Stucco Manual, EB049
- Repair of Portland Cement/Stucco, IS526
- Standard Specification for Application of Portland Cement-Based Plaster, ASTM C926-11a
It is not impossible to handle plastering repairs as a do-it-yourself project, but it is a fairly large undertaking for the average person. You can look to your local Yellow Pages, The Blue Book of Construction, or at your local library to identify contractors in your area.
NOTE: Following statement added by staff and is not an opinion of :
The best way (in our humble opinion, of course) is to contact Nurse Stucco and request a free quote.
Can stucco be applied over painted walls?
This is a common question that often arises when people are updating older construction. Stucco is a cost effective finish, relatively easily installed, that improves the appearance and creates a water resistant wall surface. A painted surface will not typically absorb water and, as such, is a substrate to which stucco will not bond—at least not uniformly.
There are two basic alternatives to covering a painted surface with a new coating of traditional cement stucco.
2) Attach paper backed rib lath or install appropriate building paper between wall and attached metal lath to provide a moisture barrier and to serve as a bond breaker. Apply traditional three coat stucco to the metal lath and accessories. In this approach, the idea is to treat the plaster like a sheathed system, using metal lath to support the stucco on the substrate, while completely isolating the stucco layer from the backup with 2-ply 60 minute building paper. This prevents a partial bonding situation, which could set up undesirable stresses in the stucco and lead to stucco cracking.
Does stucco require curing?
For cement-based materials, curing is defined as maintaining an appropriate temperature and moisture content for a specific period of time during the early life of the material. All traditional portland cement-based materials, such as stucco, require curing.
Sun and wind, alone or in combination, drive moisture out of fresh stucco. To be applied to a wall, stucco must be wet enough to be troweled, and floated, but not too wet that it sags or won’t stick. Base coats, of which there may be one or two (sometimes scratch and brown are combined), can be wetted once they have developed adequate strength so that they are not washed away by the water. Since the coats are thin, they can’t hold as much moisture as is ideal for curing—especially if they are competing with sun or wind, which both cause evaporation.
The first two days are the most critical period. The entire first week is important, however, so it is a common recommendation that the base coat stucco be misted or fogged periodically for the first three to seven days after application. If the relative humidity of the air is greater than 70 percent, moist curing may be accomplished without additional wetting of the surface.
Is it necessary to use a bonding agent with stucco?
Products that increase the adhesion of plaster to substrate or plaster to plaster are called bonding agents, and are either surface applied to a substrate or integrally mixed into the stucco.
A distinction should be made between framed construction and solid backing (such as masonry or concrete). Framed construction requires the installation of moisture-resistant paper behind the lath. There is no need to have stucco bond to the paper, so bonding agents are not used with framed construction, only solid surface substrates.
It is generally good practice to prepare the solid substrate so a bonding agent is not necessary. The prepared surface should be clean (all surface materials removed), sound (hard surface), and mechanically roughened. High-pressure water blasting is the usual process in the preparation step. If this type of preparation does not result in a clean, sound, and roughened substrate, bonding agents offer another solution.
What is the correct thickness of stucco?
Stucco thickness depends on the backup system and on whether or not lath is present. In ASTM C926, the Standard Specification for Application of Portland Cement-Based Plaster, thicknesses are provided for scratch, brown, and finish coats.
Over frame construction, lath must be used. Over solid substrates—which include concrete masonry, cast-in-place concrete, and precast concrete—lath is sometimes used. When lath is present, three-coat plaster is recommended. Note that frame construction—metal or wood studs—may or may not have sheathing present, but that plaster thickness is independent of sheathing. With lath, total plaster thickness is 7/8 inch.
Three-coat work can also be specified for solid plaster bases without metal lath. The correct thickness is then 5/8 inch.
Two-coat applications are only for use over solid plaster bases without metal lath. For unit masonry, that thickness is ½ inch. For cast-in-place or precast concrete, the thickness for two-coat work is 3/8 inch. These are direct-applied systems, meaning that there is no metal lath involved.
It is important to note that the committee in charge of ASTM C 926, the reference document for this application, has decided to keep the term “nominal thickness” in the title of the table for two- and three-coat work. This term takes into account that walls are built to certain tolerances and may not be exactly plumb or plane. The reference to a nominal thickness allows for small variations from an exact dimension. The intent of the specified thickness is to provide a reasonable system that, over many years, has proven itself to be weather resistant and durable.
Are there any temperature restrictions to stucco installation?
For best performance, the temperature of newly applied stucco should be maintained at a minimum of 40 degrees Fahrenheit. In many cases, this can be achieved by heating the structure and covering the exterior surfaces. To prevent problems like flash set of plaster, fresh mixtures should not be heated to temperatures exceeding 120 degrees Fahrenheit.
What kind of fire rating does stucco provide?
Portland cement-based plaster, commonly called stucco, has long been and continues to be a popular choice for finishes on buildings. It allows for a wide expression of aesthetics, is a cost effective finish, is durable in all types of climates (especially wet ones), and offers fire resistance. Fire resistance is typically classified by a fire rating, but what kind of fire rating does plaster provide?
Things that influence the fire rating of a plaster system include the type of material used for the support member, size of the support member, presence/absence and type of exterior sheathing, aggregate in the plaster mix, presence/absence of insulation, presence/absence of interior wall finishing materials (gypsum wallboard, etc.) and thickness of the section. The type of member—wall, partition, ceiling, or other, and member classification (load bearing(LB) or non-load bearing (NLB)) also influences the rating.
In 1991, the Foundation of the Wall and Ceiling Industry published a reference guide on portland cement-based plaster/stucco systems used for fire protection, the Single Source Document on Fire-Rated Portland Cement-Based Plaster Assemblies. Designers, specifiers, building code officials, contractors, and general public are the intended audience. The information contained therein is “not intended as design or installation criteria,” but can help people determine how to assess their assemblies using the referenced publications, fire test reports, industry standards, and codes.
For example, a typical residential application might be a three-coat system of plaster over 2-by-4-inch wood studs using metal lath attached to the studs, either with or without a layer of sheathing, like plywood. On the interior side would be a layer of gypsum board. The detail for a system made with these components is assigned a one-hour fire rating based on 1988 Uniform Building Code information.
Stucco can be painted. Portland cement-based paints are very compatible with stucco because they are made of the same material. These paints should be scrubbed into the surface and fully cured. Alternatively, you could consider a colored stucco finish. These finish coats are often made with white cement and pigments, providing the widest range of colors. Premixed materials are color matched from batch to batch and are most consistent.
Additionally, the fact that you are placing a finish coat with a nominal thickness of 1/8 inch instead of a paint layer usually gives more assurance of complete coverage. It is possible to paint with other types of paint, though these are usually not as long lasting as cement-based paint. Acrylic paints are long lasting and durable but change the permeability of the stucco (make it non-breathable) which in some climates may have adverse effects on the long-term performance of the system.
A fog coat is a light application of a cement-based slurry, the same proportions of cement, lime (if any), and water as used in the original application minus the sand, used to even out a surface’s appearance. It is typically sprayed or rolled onto the surface, similar to painting with a cement-based paint. Fog coating improves the look of stucco without changing its ability to transmit moisture vapor.
Whether you have some type of atmospheric contamination, biological growth, or staining from another construction process, stucco can be cleaned effectively. Because it is important to choose an appropriate cleaning method based on what actually created the stain, there is no single best process for cleaning stucco surfaces. You can read more here about cleaning stucco.
The Technical Service Information Bureau (TSIB) is a trade group in southern California serving the needs of the wall and ceiling industry regarding lath, plaster, and drywall. They have an excellent online resource depicting stucco textures.
The 30 textures shown on the site are accompanied by suggested application procedures. This gives material (ingredient) advice, where appropriate, and methods of applying or finishing the stucco to achieve specific appearances. For instance, the sand float finishes are described as light, medium, or heavy, and the grain size of aggregate helps achieve the desired texture. All of the textures can be made with gray or white cement, with or without pigments.
Another term for this is check cracking. Check cracking in stucco is normal. As stucco cures the water evaporates. This evaporation process causes the stucco to sleightly shrink. As the stucco shrinks the small cracks may start to appear. Environmental factors can increase the likelyness of check cracking. In hot dry weather a light spray(mist) of clean water is recommended, and may help reduce the appearance of check cracking.
Yes, new stucco can be applied and textured over an existing stucco finish. This is called recoat and restucco, and we are experts in this application. Recent advances in stucco technology and best practices in stucco application has allowed us to choose to use either traditional or synthetic stucco for the color coat. Synthetic stucco allows us nearly absolute color control, and our color lab is able to match existing colors to transform them into the color of your new stucco.
From start to finish, the average home restucco job is normally completed in under 2 weeks. This is due in part to the need for the stucco to cure between the application of the base coat, brown coat, and color coats, as well as the time to set up and take down equipment on the job site.
A complete home restucco with traditional 3-coat stucco over lath, and without the use of blown foam insulation which requires each access point in the wall to be sealed and patched, current market rate is about $20.00 – $30.00 per square yard. This is assuming the state of your walls are in average condition, and allows for some patching to be included as part of the wall preparation, as well as removal and reinstallation of rain gutters, exterior lighting, and security or communications equipment. Extra costs can come into play if extensive repairs need to be done to damaged areas of the home or if FHA screed needs to be installed before applying the stucco base coat.
The actual cost of your complete home restucco is determined by each situation. The price can vary by many factors including; thickness, texture, height of job, size of job, proximity to our supply yard, as well as application technique (hand or spray) and scaffolding requirements for OSHA compliance. For a more exact price, please Contact Us for a free estimate.
This phenomenon is normally caused from moisture being drawn from the surrounding soil. This is usually caused by the stucco coming in contact with soil and extended exposure to moisture which allows the salts and minerals contained in soil and cement based products to migrate to the surface. This can eventually deteriorate and/or cause delamination of the stucco. The most common causes are: water from Sprinklers continually soaking the wall or improper site drainage (water draining toward the wall). Moisture in the soil or water sitting at the base of the wall is traveling up the wall in a wicking action; due to a lack of Weep Screed at the bottom of stud framed stucco walls. This is frequently seen in homes built prior to early 1970’s construction boom.
This condition is common in older buildings and for this reason, the Federal Housing Authority (FHA) determined the need for “weep screed” a separation device as a remedy in new construction. For an existing structure, a separation of the stucco and the soil with the installation of a weep screed would be the only permanent solution.
You can find out more about Nurse Stucco by checking our reviews at Home Advisor and Yelp.
RESOURCE CREDIT:
Portions of Stucco Frequently Asked Questions was republished from www.Cement.org, and edited for brevity. Original resource can be read in its entirety HERE.