Reentrant cracks are the hairline cracks that can appear at comers of square openings in the stucco such as windows. Its a little sandier, at one part cement to three to five parts sand. Stucco, cracking, plaster basecoat, portland plaster. Hello everyone, in this video short video i am explaining expansion of plywood or osb sheathing, if it placed next to each other which i see 8 out of 10 times on new or existing homes, this will contribute to hairline cracking especially in the summer in areas which get the majority of the. There are a few difference between a stucco scratch coat and a brown coat. Below are some examples of some hairline cracks that have occurred. Fiberglass mesh for stucco cracks, embed or on top of brown coat february 11, 2016 by stucco plastering 7 comments hello ambitious guys and gals, who are interested in learning weather or not fiberglass mesh for stucco cracks should be embedded or placed on top of brown coat. When patching plaster, each succeeding coat is cut back further than the preceding coat, the base coat being the smallest area and the finish coat being the largest area to be patched.
Our recommended tools, the secret of spinning a hawk shown in this video, become the most popular. The brown coat surface is much smoother than the scratch coat and is gritty to the touch but flatter and looks more appealing than the scratch. Cracking is inevitable when it comes to stucco, just like any type of cement based product. Cracks that appear within the first 30 days after installation and are larger than 116 the thick ness of a penny can be filled or repaired with. We would like to have someone refinish the stucco by adding a smooth top coat to the existing stucco with a color added. Complies with astm c 926 requirements for cement based plaster. Hard float the brown coat to densify plaster membrane. Meets astm c 926 for portland cement based plaster. The coats act as a single coat, placing greater stress on the system and causing larger, deeper cracks to form. The stucco is in fairly good condition except for some small cracks in a few places california earthquake area.
Repair of portland cement plaster stucco a a a a aa aa a a a a a aa a a a a a finish coat brown coat scratch coat metal lath building paper fig. Plaster is the general term for material that is applied to a wall surface in a thin layer. For example, if the brown coat is applied to a scratch coat that hasnt sufficiently cured yet, it will cause the scratch coat to absorb water from the brown coat and continue to cure. The second, or brown, coat should go on as soon as the first coat is hard enough to accept the second coat without cracking, but at least 48 hours later, according to the irc. Aug 21, 2014 reasons why new stucco color coats crack, more common sense kirk giordano plastering inc. Hello everyone, i have a 5 year old home that had a few hair line cracks the first year. Oct 23, 20 often, when wallpaper was being applied to a rooms plaster, the brown coat was the final coat, as there was no reason for the finish coat. This minimizes the number of cracks that may come through and enhances the overall aesthetic appeal of the exterior. Consult the stucco finish manufacturer or contractor for recommended repair methods. Cracks caused by plywood are distinguished by the directions they take. This is caused by either drying too quickly, too muck water in the mix, or mixed incorrectly or applied when it was too cold or too hot the day the stucco was applied. The most traditional and popular of these types is 3 coat stucco, in which stucco is applied in three coats over metal reinforcement.
Fiberglass mesh for stucco cracks, embed or on top of. The scratch coat is applied first to provide a strong base for the system. Reasons why new stucco color coats crack, more common. I see a lot of cracks on the foam trim that is used on stucco houses quite often and. Waterresistant base used as a scratch and brown coat in nonstructural stucco wall construction. Cracks in brown coat i am using 12 sack mason cement,12 sack portland cement,and 22 shovels of sand. These cracks are a result of the stucco brown coat shrinking during the curing process. The crumbling is because the brown coat dried out before it set up, as a result of being too thin. Vibration causes cracking in concrete as well as stucco. But the whole point of the lath and brown coat were to give a viable and strong substrate to which the finish coat could be applied, while also allowing for some minor separation of the base coat from direct contact with the buildings framing members. After my contractor applied the brown coat its been over a week now i see a lot of hair line cracks and lines on one of the walls. Once the crack has been filled, fogcoat may be used to even out the color around the repaired area.
Fiberglass mesh for stucco cracks, embed or on top of brown coat. These are solid substrates which dont flex or bend like wood, they crack instead. Dec 19, 2017 no matter how great the quality of the stucco is, if its not installed right, the outcome will still be mediocre. I would really appreciate if you can share your expertise and let. The cracks look like shrinkage cracks, probably from being put on on a hot day. The scratch coat is followed by whats called a brown coat.
The various layers that make up a stucco exterior wall finish contain basically the same ingredients, but are mixed at different ratios. Hello everyone, in this video short video i am explaining expansion of plywood or osb sheathing, if it placed next to each other which i see 8 out of 10 times on new or existing homes, this will contribute to hairline cracking especially in the summer in areas which get the majority of the heat. The brown coat in the stucco process is applied over the scratch coat mostly but can also be applied over cement based substrates as well, like the scratch coat. When is it time to repair stucco cracks in the walls. Scratch and brown coat in a three coat stucco application. Repairing stucco cracks, why new stucco walls can crack. If theyre larger or more complicated than you thought, then call in an expert to take a look at them. The brown coat is followed by the finish or color coat. This stucco system consists of a scratch coat, brown coat and finish coat. 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. On any stucco job, you have to expect both the scratch coat and the brown coats to have minor cracking from shrinking. The brown coat adds strength and acts as a base for the finish coat, which can be handtroweled to create a custom surface texture. Cracks that appear within the first 30 days after installation and are larger than 116 the thick. Movement is a key cause of cracks in a cementitious color coat, decks, sheetrock, tile or comp roofs, floors, headers whether for structural or cosmetic reasons should be installed prior to the.
In winter her in norcal, no problem with a long, slow, moist cure. With stucco cracks, its always best to tackle them as soon as you see them. Our recommended tools, greeting our ambitious and faithful subscribers, as well as fellow plasterers. These cracks typically run diagonally from the apex of the comer of the opening. Same is true for installing stucco directly on a wooden lath. Key to no cracks is the tooth in of the new to old and the slow cure of the stucco coats. Dec 17, 2018 check the existing stucco for structural integrity. A scratcher tool is used to get the horizontal lines in the cement and a green float is used. Mix only quantities that can be applied within one hour. Painting stucco is an acceptable method to change color.
They ranged any where from 45 feet long to the length of my garage wall 16 plus feet between the front windows. Twocoat stucco is used on concrete, brick, and block walls. Hard float the brown coat to densify the plaster membrane. The brown coat must be compacted and hard floated to densify. The simplest crack repair method is to use the same material as the color coat. Portland cement stucco cracks develop for many reasons.
The main cause for this stucco crack is from the base coat not curing properly. The brown coat was applied three weeks ago, when we wet the surface, we see the spider cracks. The first stucco coat is called a scratch coat and as its name implies, it has a rough surface so the next coat will adhere to it. Once moisture or water gets inside a wall, it will inevitably cause further damage. It is applied with a hawk and trowel and a scratcher. The scratch and brown coats are portland cement plaster, typically each approximately 38. The brown coat properly prepares the surface making it more receptive to the color coat application. Before applying the brown coat, webber verifies the hardness of the scratch coat by dragging a nail over the wall. If cracks exceed 332 it is unacceptable and should be repaired. Hairline cracks are typically around a 116 of an inch wide or smaller, if the crack is bigger than that, than chances are that some other element is the culprit. Stucco is a somewhat colloquial term for portland cement plaster, and. First, you will want to wet down the wall where the crack is and around the area of the crack.
The rate and length of this moist curing period may vary with the weather. If vapor permeable finish coat is used, the cement base coat will cure regardless of how soon the finish is applied. Interestingly enough, the finish coat of plaster is also the thinest and most fragile. Identifying various cracks in stucco the stucco guy. Once dry, a second coat known as a brown coat will be applied and floated or smoothed to an even thickness.
Horizontal cracking on new homes, multiple hairline cracks. Shrinkage cracks are not structural and should not affect the finish coats. Nov 08, 2014 horizontal cracking on new stucco homes, cracks caused by plywood. Portland cementbased plaster is such a material that uses portland cement as the binder. Also, the mortar might have been retempered mixing water in the mortar after it starts to set. The scratch can be applied with a hawk and trowel, or sprayed on. This application of stucco is a bonding to the underlaying wire mesh and forms the base for the topcoats. Instead, wet the area and apply dry cement to the crack.
The mixture for the scratch coat, which can be done in a wheelbarrow or large bucket, is usually. In summer we hose the heck out of it daily for a month. Sure enough, it always cracks, no matter how i cure it, and no matter what time of year. Mix a small batch of brown stucco for the base coat, following the manufacturers instructions. Reasons why new stucco color coats crack, more common sense. The stucco scratch coat mix is a simple recipe that really consists. But the specific issue i was asked to look at was the stucco.
Learn how to fix hairline cracks in stucco from stucco. Sand is typically added to the stucco mix by the shovel full, baker says. The brown coat also adds strength and thickness, and it is in large part what determines the quality of the finish. However, they can provide a pathway for moisture and water to enter into a wall system.
After the cement is on the wall, a scratcher is used to make horizontal lines in the stucco mix, in order for the next coat the brown coat to stick to it. Fortunately, most cracks in a stucco system are hairline and present only a cosmetic concern. Mar 03, 2016 now that you know why stucco cracks, lets find out how serious a stucco crack can be. If mixture becomes stiff and difficult to trowel, discard it. Excessive cracking, however, usually means something was done improperly for example, the mix may have been too rich too much cement, the stucco layers may have been too thick, or the walls may not have been allowed to. How to install stucco wire 3 coat system three coat stucco. A break in the three coat stucco scratch coat, brown coat, and the finish coat application, for instance, will cause a big problem later on. I am currently in the process of stucco ing my house. Installers add decorative textures and color during the finish coat. When the wall is pressurewashed beforehand, it will have a clean surface that paint adheres to easily. Allow mixer to sit for 2 minutes, than remix for one minute. Some fine cracking can still occur in the upper coat.
Some masons skip over this step, but it doesnt hurt to spend the time for this process. Check the existing stucco for structural integrity. What do you recommend to do before the 3rd finish coat is. Excessive cracking, however, usually means something was done improperly for example, the mix may have been too rich too much cement, the stucco layers may have been too thick, or the walls may. Rainy, high humidity weather will require less wetting that will dry, windy conditions. This type of cracking is basically a sign that the base coat did not cure properly. It looks like they applied some sort of finish paintwhatever coat directly to the brown coat instead of a color coat. Allow the stucco to firm up, then scratch the surface. Repairing stucco cracks, why new stucco walls can crack youtube.
Sep 12, 2016 reentrant cracks are the hairline cracks that can appear at comers of square openings in the stucco such as windows. Merlex basex should be mixed with clean water to the consistency of exterior portland cement brown coat. Horizontal cracking on new homes, multiple hairline cracks in. From start to finish, a home re stucco job is normally completed in under 2 weeks. Properly done stucco will not crack, we use an acrylic top coat for durability and more or less permanent color. This article will give you some helpful advice on how to properly mix stucco. Professional stucco contractors who have a lot of experience in how to fix hairline cracks in stucco remove dirt and dust from the stucco wall before they begin filling in cracks. Start hairline stucco crack repair by cleaning the wall. Repairing hairline cracks in exterior stucco a helpful. No matter how great the quality of the stucco is, if its not installed right, the outcome will still be mediocre. If youre choosing acrylic stucco, a primer of paint is applied to the brown coat.
Other common repair methods may be better suited to active cracks. How to apply stucco over old stucco home guides sf gate. This could be due to the plaster drying too quickly, too much water being present in the mix, or the plaster was applied when it was too hot or too cold outside. If the nail does not dig in but leaves a white line, the stucco is hard enough for the brown coat. Stucco wall methods and choices best practices guide.
Cracks are a common and accepted occurrence in stucco assemblies but by utilizing stucco level coat with embedded mesh over the stucco base provides enhanced crack resistance to the wall. If mortar is mixed in a mixer, clean water should be used, the mixer not allowed to run too long, as the longer you mix, the faster the mortar sets. A finish coat of stucco over painted stucco depends on, condition bond of the paint, type of paint, and the finish coat being applied. Stucco cracking in portland cement plaster base coats variance. This can be accomplished one bag at a time in a bucket with a suitable drill and mixing paddle, or in a mechanical mixer.
Fiberglass mesh for stucco cracks, embed or on top of brown coat kirk giordano plastering inc. This acts as an ideal base for the finish coat, which is integrally colored in most cases and is what you see on stucco, so the base needs to be uniform. Now in the winter i am seeing more and more hairline cracks and some spider cracks but still hairline. The cement is spread evenly among the surface at a depth of about 38 of an inch thick. Although not all cracks are objectionable, cracks in stucco acceptable to one person might be unacceptable to another person. A break in the threecoat stucco scratch coat, brown coat, and the finish coat application, for instance, will cause a big problem later on. This is not recommended, a minimum 38 brown coat of portland cement plaster applied to the wall prior to the stucco color coat reduces the possibility of the grout lines telegraphing through the stucco color coat. Jul 23, 2008 there are several different types of stucco installations. This way, youll keep your stucco in good condition for years to come. There are two types of stucco houses, one that is cracked and ones that are going to. If any minor movement occurred, the separation of the finish coat of plaster from the house via the brown coat and lath was enough to keep some cracks from forming, but weve all seen enough plaster walls to know this only worked so well. Cracks are a natural part of any concretebased product, and over time all stucco installations will have cracks. Expansion, wind and stress all play vital roles in why cracking occurs. According to astm standards, the brown coat should have slightly more sand than the scratch coat.
Basic plastering skills, why, how to apply a scratch coat. Plywood installation is probably the leading cause of cracks in stucco. This will form the bonding between the topcoat and the anchoring of the scratch coat. Rapid set stucco, one coat cement plastering, professional plastering dos and donts duration. You could trowel more wet stucco into the cracks, but that quick repair tends to show. This is a leveling coat that provides the flat surface for the finished wall. Mar 22, 2012 the typical type of cracks that occur in with traditional stucco are called hairline cracks. When the base coat doesnt cure properly, it means the plaster did not dry and settle into place correctly. Water will help move the caulk around, make it squeeze into the crack and will allow you to wipe off the excess a lot easier.