What makes stucco




















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. As temperatures drop lower, plaster ingredients can be heated before mixing the stucco.

Both water and sand have enough mass to hold heat well, though it is often easiest to heat water. However, either one, or both, materials can be heated to give plaster added protection in cold weather.

To prevent problems like flash set of plaster, fresh mixtures should not be heated to temperatures exceeding degrees Fahrenheit.

Most importantly, the stucco should not be allowed to freeze during the first 48 hours after placement. Excess water in the fresh stucco mixture expands as it freezes, thereby compromising the strength and durability of the finished product. Sand can be heated over fire in a pipe, and water can be heated in metal drums.

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? The type of member—wall, partition, ceiling, or other, and member classification load bearing LB or non-load bearing NLB also influences the rating. Designers, specifiers, building code officials, contractors, and general public are the intended audience. For example, a typical residential application might be a three-coat system of plaster over 2-byinch 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 Uniform Building Code information. Association of the Wall and Ceiling Industry. Its mission is to be an active, unbiased source of information and education to support the wall and ceiling industry. The association is is located at W. 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. Use precise geolocation data. Select personalised content. Create a personalised content profile. Measure ad performance. Select basic ads.

Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Materials Finishes. Samantha is an editor who covers all topics home-related including home improvement and repair. She edited home repair and design content at websites like The Spruce and HomeAdvisor. She also has hosted videos on DIY home tips and solutions and launched multiple home improvement review boards staffed with licensed pros.

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Was this article helpful? Share your feedback. Send feedback to the editorial team. Rate this Article. Thank You for your feedback! Something went wrong. Please try again later. Our Guides. More from. As a result of changes to building codes that specified the use of WRBs, contractors should be aware that in order to function properly there needs to be a space between the stucco and the WRB so that water can dry out. If this is not adhered to as a best practice, water can get trapped and degrade the entire wall assembly, not only leading to the growth of black mold but deteriorate the structural integrity of the building.

Also, improper window flashings continue to be an issue, as the stucco cladding is most vulnerable to excessive quantities of water entering the wall assembly at window flashings and roof wall connections. You may not be aware that adhesive tape is an important tool used in exterior stucco application. Stucco composite can damage windows and frames if it accidentally comes in contact with it during the application process, so contractors make sure to mask them off using a tape that is specifically designed to keep a strong hold against plaster and withstand intense sunlight and fluctuating temperatures.

It is also important for the tape to be able to hold up heavy plastic sheeting that is used to keep windows and other surfaces clean and protected while stucco is being applied. Additionally, tape is used to create a watertight seal to protect surfaces not meant to get wet, as explained in the common problems section. Plus, one of the steps in stucco application involves applying a light spray of water over the stucco surface to help it set!

So why use specialty stucco tape instead of something more generic? It all comes down to choosing the right tool for the job. This means it needs to stand up to a multitude of elements, including sun, rain, wind and even severe temperatures, before removing cleanly. If you are involved in stucco contracting work, be sure to choose a tape designed with stucco purposes in mind in order to ensure a clean, high-quality job. And if you still have questions about stucco tape or any of our other pressure-sensitive tapes, please contact us.



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