Color coat can be applied with a trowel to create various designs or can be sprayed for a smooth finish. It can have various colors and using coarser or finer sands can change the consistencies of the final coat. An acrylic finish can be also be applied in a traditional stucco manner and has a long-lasting quality. It also comes in a variety of colors. Stucco buildings have been around far longer than you think. They originated in ancient times with Greek and Roman cultures that created stucco surfaces to paint beautiful frescoes.
These surfaces were made by combining gypsum, marble dust and glue. During the Age of Renaissance, stucco techniques were honed by the Italians and spread throughout Europe becoming one of the most common building materials.
This cement made stucco a harder, more durable material. Stucco gained acceptance in the United States in the 19th century and the word was commonly used at this time to describe exterior plastering. Historians believe that there are a couple of reasons why stucco became so popular. Stucco is a fairly inexpensive material.
A good artisan could use stucco to emulate fine stonework and patterns. Traditionally, stucco is mixed on-site using bulk materials. The trick to creating your own stucco mix is getting every batch exactly the same. A basic stucco mix consists of:. The slower stucco dries, the stronger it becomes. In sunny and hot locations, stucco must be shaded to prevent the dehydration of the stucco mix.
Never apply stucco if the weather temperature is lower than 40 F. There are many major manufacturers that you can contact for more information on mixing and applying stucco:. Stucco can be mix with pigment to create a range of colors, or it can be used without pigment and simply bear the natural gray of its cement. Some contractors tend to use warm colors, such as yellow, pink, or orange, but beige and white are perhaps the most common colors used for stucco.
Stucco can be painted, but it must cure for at least six weeks prior to painting. Coloring stucco with pigment is far preferable to painting it because paint creates a regular maintenance issue, while pre-mixed coloring is permanent.
Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. 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 placement.
A sheet of polyethylene can be placed over the moistened surface to hold the water in. If the relative humidity of the air is greater than 70 percent, moist curing may be accomplished without additional wetting of the surface.
A caution about moist curing is that colored finishes can be affected by water application. Finish coat stucco is not moist cured since this may promote mottling and discoloration. Curing of colored finishes is typically done by wetting the base coat to provide curing moisture from behind the finish and ensuring that the surface is shielded from drying.
Proper curing also requires that plaster be in a medium temperature range. Too cold and there is a risk that water in fresh plaster would freeze. As this is an expansive process, cracking could occur. Cement hydration can be interrupted, too. Too hot and there is a risk of drying—which, like freezing, can also suspend cement hydration—or of accelerating the hydration process to a point where strength development in the longer term is negatively impacted.
Curing compounds are effective for concrete but are not used regularly on plaster. These materials might interfere with subsequent coats of plaster and might lead to discoloration of the stucco finish. Stucco is a popular and cost-effective finish. When placing plaster over insulating concrete forms ICFs , it is recommended to treat this substrate as any other sheathed system. It should include building paper, metal lath, and three-coat portland cement plaster.
In this way, plaster is properly supported, yet free to move independently of the substrate beneath it. Some insulating concrete forms contain embedded furring strips on their face. After placing paper over the face of the ICF, metal lath is mechanically fastened to the furring strips. The lath supports plaster and holds it in position while the paper isolates the plaster from the foam.
Although plaster would adhere to the face of the insulating concrete forms, the weight of the layer is more than should be supported by foam. The plaster could settle or shear entirely off the face of the wall. 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 plaster.
If contamination is present on the substrate surface, good bond is inhibited. This is generally not a concern with new masonry walls, but can be an issue with new cast-in-place concrete as it may have residual form release agent on its surface. Older concrete or masonry walls may have bond-inhibiting characteristics, in the form of paint, sealer, some other coating, or dirt on the surface. As such, bonding agents are more likely to be considered for repair and renovation work over either concrete or concrete masonry.
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. Methods for achieving these criteria include sand blasting and high-pressure water blasting. If this type of preparation does not result in a clean, sound, and roughened substrate, bonding agents offer another solution. Rather than using bonding agents, another option for low-absorption surfaces is to apply a dash bond coat.
This cement rich slurry is dashed against the base surface by hand with a brush, trowel or paddle, or by machine. Most of the surface is covered with the plaster. The high cement content provides a tenacious bond. This material is left unfinished so that a rough base is created for the scratch coat. Industry documents contain guidelines for placing each coat of stucco in two coat or three coat systems.
The recommendations are there to ensure 1 proper curing and 2 strength development of the previously installed coats. To cure cement-based materials means to allow them the opportunity to hydrate, and this requires both adequate moisture and proper temperature. Exterior plaster has more stringent requirements because it is typically subject to more severe exposure than interior plaster.
There are two related, but distinct, reasons for delaying application of a subsequent layer of plaster on top of a previously installed layer. One reason is that there has to be adequate moisture retained in each layer.
Usually, this is accomplished by misting the plaster once or twice during the day. It can, however, be adequately accomplished by preventing evaporation of moisture from the plaster—and placing the next layer of plaster on top of the other does that. This exception to the rule—referred to as a double-up or double-back procedure—allows for more efficient labor practices. The wording indicates that a second coat of plaster brown coat can be applied to the first base coat scratch coat as soon as the first coat has attained sufficient rigidity to receive the application without damage.
This often occurs on the same day see the footnote to the table above. Curing of the second coat then proceeds per the table. Following guidelines for curing and delay between coats usually result in the most consistent surface finish—uniform texture and color. Stucco thickness depends on the backup system and on whether or not lath is present.
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. Three-coat work can also be specified for solid plaster bases without metal lath. Two-coat applications are only for use over solid plaster bases without metal lath.
These are direct-applied systems, meaning that there is no metal lath involved. 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.
Local building officials should be consulted for further information about variations from the specified thickness. See www. In new construction, the structural system usually has more than enough strength to support installed plaster.
In buildings that are being updated or retrofitted, however, stucco may be placed over existing construction. Concrete or masonry walls generally have sufficient structural strength to support the additional weight. In wood frame construction, support members studs should be checked to ensure they can carry the extra load. A typical plaster mixture weighs about pounds per cubic foot, roughly the same as mortar, and this amount of material would cover about The metal lath may add a small additional amount of weight, so the end result is that three coat stucco weighs about For more information about the unit weight of plaster or installed weight, see Tables 1a and 1b on p.
The proper use of contraction joints in stucco systems will depend on a number of variables, including: the type of construction materials to which the stucco will be applied; the orientation of the construction—vertical walls or horizontal ceilings , and whether the surface is curved or angular. Stucco may be direct applied to concrete or masonry substrates; however, if these materials are used together, as in the case of a concrete framework of beams and columns with masonry block infill, a joint may be required at the transition of one material to another.
Stucco that is direct applied to concrete or masonry requires contraction joints only where there is a change in material or where there are joints in the concrete or masonry structure. Metal lath may be used over concrete or masonry construction and should be used in sheathed frame and open frame construction.
When stucco is applied to any construction using metal lath, joint spacing recommendations should be implemented. Applications that use metal lath require three layers of plaster: scratch, brown, and finish coats. Currently, per the building code, a portland cement plaster is only required to have a weather resistant barrier WRB behind it, which is satisfied by the ICF; hence, building paper would not necessarily be required. Therefore, best practice indicates isolating the two materials from each other to allow independent movement and reduce stresses that might otherwise lead to cracking in the plaster layer.
By using a permeable paper, the permeability of the wall system remains unchanged. If it is desired to apply a finish directly to the foam form, an exterior insulation and finish system EIFS material may be considered. These finishes are thin, lightweight, and tough. Although the thinner exterior insulation and finish system materials can be direct-applied, moisture management then becomes even more critical. If an EIFS coating is chosen, openings windows, doors, etc. Stucco is known to be a weather resistant building finish, but it is part of a system.
In order for the wall to resist water penetration effectively, the system must be properly designed and detailed, then built according to plans.
The main purpose of building paper is to keep water from contacting the substrate and structural support members—very commonly sheathing like plywood or oriented strand board OSB and wood or metal studs—so that these materials stay dry.
Metal can rust and wood can rot. Minimizing the changes in moisture minimizes the stresses that might be placed on plaster from behind. In addition to structural considerations, excess moisture within a wall creates a potential for mold or mildew inside buildings.
Building paper prevents moisture-related problems in stucco walls. During construction, paper can be damaged.
Paper should be lapped like siding, meaning that upper layers are placed over lower layers. This facilitates drainage toward the outside. Where the edges of paper-backed lath meet, connections should be lath-to-lath and paper-to-paper. This specification differentiates weather resistive Kraft papers by types, grades, and styles. Grade D is a water-vapor permeable paper. Grade D paper with a water resistance of 60 minutes or more works well for stucco applications, and is often preferred to Grade D paper having the minimum minute resistance required by UU-Ba.
Some specifiers are turning to house wraps for stucco underlayment. While these materials may be more rugged than paper—and therefore less prone to damage during installation—a single layer is still not adequate according to many industry professionals. At best, a hybrid system, with the house wrap closest to the sheathing and covered with the paper, seems to be an acceptable alternative. 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.
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