Stucco FAQ

Information Bulletin Regarding Stucco Cracking

Stucco is a colored cementitious material that is hard, brittle and water resistant. One might be fearful of cracks in stucco, but stucco has cracks like wood has knots. Cracking is inherent to the product. 
  
The Stucco Manufactures Association recommends that stucco systems, be panelized every 150 to 200 square feet to control cracking.  This is generally accomplished with expansion joints during initial construction.  This type of panelization is normally accomplished on commercial buildings, but due to aesthetic considerations, rarely seen on residential homes. Adobe style homes with parapets will generally not have any type of expansion joints installed.  Panelizing the stucco allows for the stucco to move as a single unit, within the panel, while minimizing cracking. When stucco is applied to larger areas, it will generally crack to relieve the stresses generated within the material from, thermal expansion and contraction, wind loading, moisture freeze / thaw cycles and movement of foundations from tree roots, seasonal heaving and receding and settling during the first few years after a structure is built. Cracks will typically appear at the corners of windows and doors and can extend diagonally for a couple of feet. Areas of dissimilar materials such as the transition of block walls to a wood framed structures will experience different rates of expansion and contraction and usually a crack will develop at this interface. When room additions are constructed against an existing structure, it is common that that the new and old structures are not completely married and therefore movement will take place and a crack may develop at that interface.  Many times cracking will develop at the “sill plate” which is were the house wall systems sit on the concrete foundation. These cracks are easy to identify as they will appear approximately six to twelve inches above the grade and extend perfectly horizontal, sometimes for many feet. 
When a structure has been restored with a new stucco color coat, the colored cement stucco material is approximately 3/16” thick.  Some preexisting cracks may have been repaired prior to the color coat but other times the color coat may fill minor cracks and offer a better aesthetic solution. The new color coat is mostly aesthetic, not structural, and will help to bridge some of the cracks that have stabilized, but can typically re-crack due to movement in the wall by the above mentioned causes.  Cracks can occur immediately after a stucco restoration has been accomplished.  If the wall is not moving, the stucco will generally not crack.   Cracking is not always a problem for the integrity of the stucco system.  The general rule of thumb is that cracks on the vertical wall surface, less than a width of a nickel (1/8” thick), are considered hairline and do not pose any threat to the integrity of the stucco system.  Cracks on the vertical walls that exceed 1/8” and extend into the base coats should be addressed with a good crack patching procedure.  Cracks of any size on parapet caps should be sealed promptly to avoid moisture intrusion. 

Even premium synthetic stucco systems such as Sto, Synergy and Parex to name a few are more resistant to cracking, but if applied over a cement base, cracking will most likely occur.  This should not necessarily be construed to be a failure of the material or application.  Synthetic stucco finishes are more elastic, and will tolerate more movement in the wall than cementitious stucco finishes, before they are breached, but still they are subject to the same physics as cement stucco finishes. 

Considering cracking will at some point in time occur to all stucco and synthetic stucco systems applied over a cementitious base, manufactures or contractors do not warranty against cracking.  A successful regiment of water management and periodic maintenance should give one many years of durability and satisfaction, for a well applied product. For a crack repair procedure, please see the accompanying bulletin on “Caulking of Stucco…Tech Bulletin” or feel free to call us at 505-345-3200, if you have any further questions. ​

Stucco Color and How it Will Change

Once a stucco color coat is applied, it will remain wet for a period of time, and appear darker than the final dried and cured color. After the stucco completely dries, it will then appear lighter and have a slight chalky appearance. The color will continue to cure and darken with a majority of the color achieved within a seven to ten day period, although it can take several months for it to closely blend to the manufacturer's color chart. The color pigments in stucco oxidize with the interaction of the atmosphere and moisture, which creates the rich colors of the Southwest that we have grown accustomed. This oxidation process continues for many years and ever so slightly, the stucco will continue to darken, even after the initial cure.
 
The initial curing process can be artificially accelerated to cause the color pigments to stabilize, darken and reach a cured state sooner than by natural means. The term for this process is called a "water cure" and is the action of misting the stucco with water from a hose. It should only be accomplished after the stucco has completely dried and within a temperature range that will allow the stucco to mostly dry out before nightfall. With a hose nozzle set to mist, the surface must be misted uniformly corner to corner and the water should not copiously run down the wall. This process can be accomplished once a day for three to four consecutive days to cure and set the color. This procedure also helps the stucco to gain strength sooner than if left to cure naturally. If you choose to accelerate the cure by this method, please call our office at 505-345-3200 so that we can offer you guidance, as weather conditions may affect this procedure.

Technical Bulletin for Crack Repair for Synthetic and Cement Stucco

Crack repair for either synthetic or cement stucco products should be addressed if the crack exceeds 1/8” wide (the width of a nickel) or greater on vertical walls and extends into the base coat, and for any size crack on parapet caps, flat wall surfaces. If the crack is less that 1/8” wide on a vertical wall, the repair is optional and would be mostly for aesthetic consideration.

Materials and tools needed:
            Sponge
            Duct tape or masking tape that will adhere to the wall surface
            Small pail or container with water
            Butter knife or optionally a tool called a caulking spatula. 
            Flat head screw driver
            Rags 
            Colored caulking 
            Caulking Gun
            Painters mineral spirits (Only necessary for urethane caulk for tooling).
            Lacquer Thinner or Toluene (Only for clean up of urethane caulk)
            Stucco Fog Coat – (Only for stucco crack repair, not synthetic)
            Backer Rod (foam rope on a roll) - For cracks exceeding ¼” wide.
            1” to 2” Paint brush.

Caulking Choices:
There are several choices for the type of caulking you may use for crack repair.  Pure silicone is not recommended. Exterior grade acrylic / silicone blend, often referred to as paintable caulk, is a water base product and is the easiest to work with, and cleans up easily with water. For homeowner application, acrylic / silicone is mostly recommended for its ease of use while being able to achieve a good result. Urethane is more difficult to work with, but offers superior performance than acrylic / silicone blends.  Whatever your choice, purchase the highest quality (the longest year indicated on the label) available. You will need to ask for a “Non Sag” caulk that is stiffer and will stay in the crack as opposed to a self leveling caulking that is more viscous and will run down a vertical surface. Most caulking offered at Home Depo or Lowes is non sag. 

It is important to purchase a caulking that blends as close as possible to your wall color.  With small cracks, the color is less important than with larger cracks.  If it is important to achieve very close blend to the wall color, a blended exterior paint or a synthetic finish compatible with the caulking can be applied over the caulking, once it dries.

Caulking can be purchased at Home Depo or Lowes for standard colors and for a larger selection of colors at, Pro Build located at 4200 2nd St NE, Albq., Ph: 345-1755, or in Santa Fe at 1137 Siler Rd.,  Ph: 471-7474; Chaparral Materials Inc. located in Albq., at 912 1st St. NW or in Santa Fe at 5946 Agua Fria, Ph: 471-3491 and  Smalley  & Company  located  at 8920 Adams NE, Albq.,  Ph: 797-7222.

Fog Coat can be purchased at Hope Lumber, Home Depo, New Mexico Plaster Supply located at 4100 4th St. NW, Albq., Ph: 345-6881, or Chaparral Materials Inc. located at 912 1st St. NW, Albq., Ph 217-1051, or in Santa Fe at 5946 Agua Fria, Ph: 471-3491. For our market, El Rey Stucco and Western Blended Products are the two major brands of stucco and the associated fog coat colors that are available. If you know either the brand and or color of stucco that is on the wall, it is best to first attempt to procure that brand of Fog Coat, so as to achieve a closer color blend. Fog Coat comes in a plastic pail and is the raw pigment of the bagged stucco, and looks like a colored powder. 

Repair Procedure:

1. With a screwdriver, lightly remove loose material at the margins (edges )of the crack. Do not rout, gouge or enlarge the crack.
2. With tape, mask off on either side of the crack as close as practical, to protect the surrounding wall area from the caulking product.
3. Cut off the tip of the caulking tube to reveal a small hole at first, or a hole size that will allow the injection of the caulk into the crack with one pass. 
4. With the colored caulking in the caulking gun, inject the caulking into the crack by pulling the caulking along the crack line.  Do not build up the caulking too much past the plane of the wall. 
5. The caulking now needs to be tooled down. For acrylic caulking this is best done with a wet finger.  For urethane caulking, dip the butter knife or spatula into mineral spirits and draw the knife tip or tool over the caulk, knocking the caulking bead down flat and even with the wall surface. 
6. The caulking is most effective, when it is adhered to just the sides of the crack. Leaving excess caulking on the surface or beyond the edges of the crack, makes the repair less effective and re-cracking of the caulking is more probable. With acrylic / silicone caulk, use a damp sponge to wipe off the excess caulking from the wall surface by wiping across (perpendicular) to the crack to remove excess caulk from the surface, leaving only the caulk in the crack. With urethane caulk do not wipe with a sponge, use only the butter knife or spatula to tool.
7. For stucco walls, “Fog Coat” can be broadcast by hand or dabbed into the wet caulking with a paint brush that has been loaded up with fog coat, to blend the color and to create a more realistic stucco appearance. 
8. Clean up for  acrylic / silicone caulk is done with water. For urethane caulk clean up is best achieved with lacquer thinner or toluene. Exercise caution with these products. 
9. Remove tape and you are done.
10.  With any of the products mentioned above, be sure to follow the recommended procedures on the packaging. 

Crack repair that exceeds ¼” should utilize urethane caulking. It will be necessary to use a backer rod to create a backing for the caulking for the caulking to obtain an optimum depth. Backer rod comes on a roll and comes in varying diameters, depending on the size of the crack or gap being sealed.  It is best to check with Smalley and Company for the recommended size of backer rod, based on your requirements.

Chimney Runoff Diverters for Pitched Roofs

Once you have had a new stucco color coat applied, there are several preventative measures that will preserve the integrity and aesthetics of your stucco.  As a matter of preventative maintenance, the “Homeowner Maintenance Tips “ (accompanying bulletin) should be followed. With cement stucco based products, water is the enemy. By redirecting sprinklers, adding gutters, installing down spouts and water diverters and generally keeping the water away from the stucco wall surfaces, your stucco should give you may years of trouble free performance. 

A common problem that requires special attention is at chimney areas. On pitched roof homes, water can run off of the shingles and flow onto the sides and angled surfaces of the chimney.  The action of the dirt being washed off of the roof, and the high concentrations of moisture absorbing into the stucco, will almost always cause the stucco to stain and effloresce (exhibit whitish residue).  If left unattended, this condition will eventually compromise the integrity of the stucco bond. To avoid this problem, we highly recommend that at a minimum, diverters be installed on the shingled roof, upside of the chimney. Typically  two each  2” x 2” x 10’ “L” angled sheet metal flashings are sealed to the roof shingles in a “V” pattern to direct the water flow from the roof, away from the chimney.  A competent roofer can accomplish this flashing detail.  Installation of gutters adjacent to the chimney is also helpful. Gutters and downspouts for all homes will help to direct and keep the water away from your stucco.  By simply directing water sources away from the stucco, you will enjoy many years of protection and beauty from your stucco finish. 
​
Please feel free to call us at 505-345-3200  if you have any further questions.

Stucco Parapet Maintenance

With flat roof architecture, this stucco to roof transition also known as the parapet, is the most problematic with regard to periodic maintenance. 

A typical stucco system on most wood framed  homes includes, a moisture resistant barrier of asphalt impregnated paper over a wood sheathing, stucco netting, cement base coat(s) and a cosmetic colored stucco finish coat also known as a color coat. This stucco system will perform well under most adverse weather conditions but is not designed to be a “waterproof system”.  By design, homes in the Southwest have parapets and flat areas that allow water to be retained and undergo freeze thaw cycles.  This action breaks down the stucco and will eventually cause cracking, deterioration, and eventually leaks through the stucco.

With an existing stucco system or even a newly applied cosmetic stucco color coat, the parapet requires annual homeowner maintenance to insure a trouble free system.  Understanding that cement stucco will crack and roof flashings will breach, the following maintenance regiment is recommended; 1) Seal any visible cracks on the parapet with an acrylic/ silicone or a polyurethane caulking. Polyurethane caulk is preferred but a bit messier to work with.  For additional caulking recommendations, please see the accompanying “Caulking of Stucco… Tech Bulletin”. Keep in mind that it is best not to extend the caulk too far over the front face of the parapet, where it will be visible from below and 2) Re-seal the roof flashing to the parapet. This is typically accomplished by applying plastic roof cement to any breaches or breaks that are evident at the stucco to parapet transition. A silver paint sprayed over the plastic roof cement will help to extend the life of the product. 

If these maintenance items have been accomplished and you are still experiencing problems, testing of the roof is in order. A competent roofer may conduct a test by flooding the roof and flooding any other transitions to roof penetrations with water to pinpoint a roof leak.

If you have any further questions on any stucco or window related issues, feel free to call us at 505-345-3200.

Sto Stucco Restoration and Crack Repair Specification R 300

PART 1 GENERAL
1.01   Summary
A.         The general conditions, supplementary conditions and general requirements of these construction 
            documents apply to the general contractor, subcontractors, material suppliers and all persons 
            furnishing labor and materials under this section.
B.         Section Includes: description of requirements for materials and installation of stucco repair system
            as shown on drawings and as specified herein to complete work.
1.02  Description
A.         Design Requirements:  the structural wall system to which the stucco repair system is attached shall
            meet L/360 maximum allowable deflection criteria and applicable building code requirements.
1.03  Submittals
A.         Submit copies of manufacturer’s specifications, installation instructions and product data.
B.         Submit copy of applicator’s certificate of training, where training is required by manufacturer or
            product specifications.
C.         Submit samples for approval as directed by architect.
D.         Submit copy of manufacturer’s warranty.
1.04  Delivery, Storage and Handling
A.         All coating materials shall be delivered in their original sealed container bearing manufacturer’s name 
            and identification of product with written application instructions and appropriate health, hazard and
            safety data.
B.         All ready-mixed coating materials shall be protected from extreme heat, sun and frost.  Factory      proportioned bagged materials shall be stored inside, off the ground in a dry area and protected  from 
            moisture.
1.05   Job Conditions
A.         All materials shall never be applied if ambient and surface temperatures cannot be kept above
            38 degrees F during application and drying period.  For installation in temperatures less than
            30 degrees F supplementary heat shall be provided.  The installed materials shall be protected from
            exposure to rain and freezing until dry.
PART 2 PRODUCTS
2.01   Material-General
A.         Manufacturer’s:  materials are specified by brand names to establish a standard quality, or by performance
            requirements and general description of the product.  The architect will consider substitutions for brand        names of  products specified, provided the procedures set forth for substitutions are followed.  The      architect reserves the right to reject any material which, in his or her opinion, will not produce the quality              of work specified herein.
B.         The following are acceptable manufacturers:
            STO CORP.
2.02   Surface Preparation
   
A.         Conditioners
            
1.         Sto Plex W - a ready-mixed water based surface conditioner with minimum solids content of  8% for
            treatment of dry, porous stucco/plaster  surfaces and load bearing painted surfaces.
2.         Sto Bonding Agent - a water based resin dispersion designed as a surface preparation for dry/porous
            concrete, masonry or stucco surfaces.  Also serves as an additive to Sto One Coat Stucco.


2.03 Patching, Leveling and Resurfacing
A.         Sto Leveler - a one component factory proportioned polymer modified fiber reinforced cement based 
            leveler with water repellent additive for pre-filling surface cracks up to 1/4 inch wide and for leveling,
            patching or filling surface irregularities up to 1/2 inch deep in one application.
2.04   Waterproofing
A.         Sto Flexyl - a 100% acrylic copolymer based waterproofed for use with Portland cement and Sto Mesh
            to waterproof parapets, sloped sills and other areas that require a waterproof membrane to prevent 
            water intrusion.
2.05   Crack Repair Materials
A.         Sto Flexjoint Compound - a ready-mixed elastomeric acrylic dispersion based joint compound and 
            ground coat for filling surface cracks up to 1/8 inch wide and for use as a ground coat with Sto LPA Mesh
            to reinforce surface cracks up to 1/16 inch wide.
B.         Sto Flexyl - a 100% acrylic copolymer based waterproofer and stucco crack repair for use with Portland
            cement and Sto Mesh to fill and reinforce surface cracks up to 1/16 inch wide.


3.   Elastomeric paints:
A.         StoSilco Lastic - a silicone emulsion elastomeric flat paint for concrete, masonry, plaster or existing          acrylic based textured finishes; for brush, roller or spray application.  Minimum solids content shall be               60%.  Dry mil thickness shall be 15-17 mils in two applications (prime coat and finish coat).
Note:  Type, texture and color of paint shall be as indicated  on architectural drawings or per approved sample  
           submittal.  Color shall be identified in accordance with the Sto Color System and color fastness shall be a
           minimum of 8.  Lightness value shall be 30% or greater for Sto silicone based finishes.
2.06   Reinforcement
A.         Sto Detail Mesh - a symmetrical, interlaced glass fiber made from twisted multi-ended strands, and coated    to be compatible with Sto repair materials. 
B.         Sto Mesh - a symmetrical, interlaced glass fiber made from twisted multi-end strands and alkaline
            resistant coating, at least 20 grams per square yard, for computability with Sto materials.  The mesh shall
            weigh 4.8 oz./sq.yd. (162 g/m2) and shall be shiftproof with trimmed roll edges to minimize buildup on 
            overlapped seams.
2.07   Primer 


A.         STO PRIMER - a ready-mixed elastomeric acrylic dispersion based primer with fine aggregate that             can be tinted to match the finish coating; for use prior to the application of Sto acrylic textured finishes.
Note:     Priming is recommended to reduce substrate  absorption and to enhance finish color, to improve adhesion
            and water resistance, and to retard efflorescence in cementitious substrates.  Appropriate tinted primer is
            recommended as a color base for “R” (rilled textured) finishes and all fine aggregate (less than 1mm)
            finishes.
2.08  Textured Coating  (select one, depending on type, texture desired)
A.         Sto elastomeric textured coatings:
            1. STOSILCO FLEX - a ready-mixed silicone based elastomeric textured wall coating with graded marble
            aggregate (as listed below) for trowel or spray application.
                                    Texture                                      Aggregate Gradation
                        Stosilco Flex 1.0                                                 .8-1.2mm
                        Stosilco Flex 1.5                                                 1.2-1.8mm
                        Stosilco Flex R1.5                                                    1.2-1.8mm
B.         Type, texture, color and aggregate size of coating shall be as indicated on architectural drawings or per 
            approved sample submittal.  Lightness value shall be 30% or greater for Sto silicone based finishes, 20%
            or greater for all others.
2.09   Performance Criteria
A.         All materials shall meet or exceed the minimum performance criteria listed in this specification:    
1. Stucco Patching/Leveling/Resurfacing Material* (Sto One Coat Stucco or Sto Leveler):
TEST                                              METHOD                        RESULT   
   
Compression Strength                  ASTM C - 109               Greater than 4000 psi
Tensile Strength                          ASTM C - 190               Greater than 300 psi
Flexural Strength                         ASTM C - 293               Greater than 1000 psi
Water Absorption                        ASTM C - 642               Less than 3%
Surface Burning                           ASTM E - 84                 Flame spread - 0    Smoke developed - 0
*all results @ 28 days


2. Waterproofer and Stucco Crack Repair Ground Coat  (Sto Flexyl):
TEST                                              METHOD                       RESULT
Tensile Strength                          ASTM D - 412               300 psi
Elongation                                 Lab method                    7.7% (w/o mesh)
Adhesion to cement board              ASTM C - 297               100 psi
Adhesion to concrete                    ASTM D -4541               90 psi
Adhesion (in peel) to concrete        ASTM D - 903               20 lb.
Vapor Permeability                      ASTM E - 96                 1.20 US perms
Mandrel Bend                              ASTM D - 522               pass @-30 degrees C, 0 degrees C, 30 degrees C 
        
Hydrostatic Pressure                     Lab Method                    no water penetration at 7 bar (230 foot height
                                                                                                water column) after 24 hours.
Waterproofing                             ASTM E - 514                    no water penetration after 8 hours exposure
UV Resistance                            ASTM D - 822               no degradation
Surface Burning                           ASTM E - 84                 flame spread: 25              
                                                                                                smoke developed: 70
3.   Elastomeric joint  compound (Sto Flexjoint Compound)
TEST                                        METHOD                      RESULT
Tensile Strength                          ASTM D - 412               60 psi
Elongation %                              ASTM D - 412               500%
Recovery @ 100% elongation        ASTM D - 412               70%
                                                            (10 min. recovery)
Shore “A” Hardness                      ASTM D - 2240              25 - 30


4.   Silicone based elastomeric paint (StoSilco Lastic) :
TEST                                        METHOD                      RESULT
Accelerated Weathering                 ASTM G - 53                 no noticeable yellowing or deterioration 
                                                                                    or delamination @ 2000 hours.
Freeze/Thaw                               Lab method                    no cracking, discoloration or loss of film
                                                                                    integrity after 25 cycles
Tensile Strength                          ASTM  D - 412              135 psi
Elongation                                 ASTM D - 412               280%
Recovery at 175 % Elongation       ASTM D - 412               80%
Water Vapor Transmission            ASTM D -1653               9 - 10 perms @ 20 mils
                                                (method A)
Adhesion                                    ASTM C - 297               145 psi (wood)
                                                (modified)                       greater than 45 psi (steel)
                                                                                    greater than 140 psi (concrete)
Water Absorption                        DIN 52 617                    .054 kg/squ m/24 hr @ 3 weeks
TEST                                        METHOD                      RESULT
Intercoat Adhesion                       ASTM  D - 3359             5
                                                (modified)
Shore “A” Hardness                      ASTM D - 2240              35 - 40
Mildew Resistance                       ASTM G - 21                 no mildew growth at 21 days
Crack Bridging                            Lab Method                    6.34 mils at 77 degrees F
Low Temperature Flexibility         ASTM D - 522               pass at -30 degrees C
 
5. Silicone Based Elastomeric Textured Coating  (StoSilco Flex SW1)
TEST                                        METHOD                      RESULT
                                                                                                
Accelerated  Weathering                ASTM G - 53                 No deterious effects after 2000 hours.  No noticeable
                                                ASTM D - 659               yellowing. Chalk rating = 9 (10 is best on a scale of
                                                ASTM E - 313                1 - 10 )
                                                 (yellowing)
Elongation                                 ASTM D - 412               500% *
Tensile Strength                          ASTM D - 412               60 psi
Adhesion to Concrete                   ASTM C - 297               120 psi
                                                (modified)
Flexibility                                  ASTM D - 522               pass at 1/8 inch mandrel bend at - 30 degrees F
Freeze/Thaw Resistance                Lab Method                    no change after 25 cycles
Water Vapor Permeance                ASTM D - 1653              34 perms
Mildew Growth                           ASTM G - 21                 no growth
Chemical Resistance                    ASTM D - 1306              good resistance to Mild Acids, Alkalis and Salts
Resistance to Dirt Pick-up             Lab Method                    98% reflectance retained
Wind Driven Rain                        Fed Spec TT-C-555B        pass
Surface Burning                           ASTM E - 84                 Flame Spread: 5
                                                                                    Smoke Developed: 5
*elongation of neat film
*all results after 7 days
        

2.10   Mixing
A.         Sto Plex W - mix with a clean, rust-free high speed mixer.  Add water as directed on labeling.
B.         Sto Bonding Agent - As a bonding agent, agitate container and use undiluted.
C.         Sto Leveler - mix with 6 -7 quarts of clean potable water per 60 lb. bag, allow to set for approximately 
            5 minutes, adjust mix  if necessary, then remix to a uniform consistency.
D.         Sto One-Coat Stucco - mix approximately 200 lb. of sand to an 80 lb. bag of Sto One -Coat Stucco.  Add preblended dry mix to 5 -7  gallons of clean potable water.  mix with paddle type mortar mixer to a uniform consistency.
E.         Sto Acrylic One-Coat Stucco - dilute Sto Bonding Agent  with 3 parts water to one part Sto Bonding  Agent (by volume).  Follow normal mix ratio and procedures for mixing Sto One-Coat Stucco, except use 5-7 gallons of diluted Sto Bonding Agent in lieu of water.
F.         Sto Textured Finishes - mix with a clean, rust-free high speed mixer.  A small amount of clean water may
            be added to aid workability
Part 3   EXECUTION


A.         All installation of Sto materials shall be performed by and/or supervised by Sto Instructed* Applicators.
B.         Under no circumstances shall any of the products be altered by adding any additives, except for small
            amounts of clean water as directed on the label. Antifreeze, accelerators, rapid binders, aggregates, etc., are forbidden.
C.         The surface to receive the stucco repair system shall be structurally sound, clean, dry and free of residual 
            moisture or damage from moisture.  Surfaces shall be properly cured and free of dirt, dust, oil, grease,
            mildew, fungus, laitance, efflorescence and any other contaminant.  Any surfaces not in compliance shall
            be corrected prior to installation of the stucco repair system:
                        1.  Surface contaminants must be removed by wire brush, sandblasting, waterblasting or other
                             appropriate means.
                        2.  Efflorescence may be removed by a diluted acid wash and rinse, or other appropriate means.
                        3.  Treat dry, porous, or absorbent surfaces with surface conditioner.  (Use Sto Plex W for highly absorbent, sanding surfaces and chalking surfaces.)
                        4.  For painted surfaces: paint must be removed by wire brush, sandblasting, waterblasting  or
                             other appropriate means.  Alternate procedure for LOAD BEARING painted surfaces ONLY: 
                             treat with water based surface conditioner.
                        5.  If patching, filing or leveling of irregularities is requited, and to repair loose, deteriorating
                             plaster, concrete, or mortar, repair with appropriate leveling material to thickness required to achieve a smooth, plumb surface.


D.         Crack Repair and resurfacing of cementitious stucco:

1. For cracks up to 1/16 inch, reinforce with minimum 6 inch wide mesh embedded in elastomeric ground coat. For larger cracks, clean out loose material with trowel, prime inside  surfaces of crack with diluted bonding agent and fill with stucco patching/leveling material.  Allow to dry and reinforce with minimum 6 inch wide Sto detail mesh embedded in ground coat.

Note:  If cracks are widespread throughout the wall area reinforce entire area with Sto mesh embedded in
          Sto Leveler or elastomeric ground coat.

1. After properly preparing surfaces, patch/level all voids or surface irregularities with a trowel application of the patching/leveling surface.  Where adverse drying conditions exist (dry climate and/or temperature above 80 degrees F, damp cure the area to prevent shrinkage and enhance material strength.

 .     When resurfacing entire wall area, prepare surfaces in accordance with Section 3.01C.  Apply stucco 
       resurfacing material by trowel or with proper spray equipment to a maximum 3/8 inch thickness in one
       application. Apply second coat if necessary to achieve a smooth, plumb surface as soon as the first coat is
       firm enough to receive the second coat without physical damage.  Alternatively, damp cure the first coat
       for 48 hours, then apply the second coat.  Level with a darby or stainless steel trowel.  Damp cure by lightly
       fogging the installed area for at least 48 hours after initial set (usually within the first 1 to 4 hours after 
       installation).  DO NOT INSTALL DURING EXTREMELY HOT, DRY AND/OR WINDY CONDITIONS
       DO NOT INSTALL OVER DISSIMILAR MATERIALS OR JOINTS IN CONSTRUCTION.  Allow to dry 
       prior to application of primer or finish.
F.         Waterproofing:  any areas requiring a waterproof membrane, such as sloped sills or parapets, shall be
            treated following crack repair/leveling or resurfacing and prior to application of the textured finish:

1. Apply ground coat with stainless steel trowel to a uniform thickness of approximately 1/16 inch. Work horizontally or vertically in uniform strips of 40 inches.

                        2.   Immediately embed reinforcing mesh in wet ground coat and feather out seams and edges.

1. Double wrap reinforcing mesh at all corners and overlap at the seams not less than 2-1/2 inches. 
2. Apply mesh a minimum of 6 inches beyond sloped sill terminations or down both sides of the parapet (where stucco is on both sides).
3. The finished thickness of the ground coat shall be such that the mesh is fully embedded.  Allow to dry prior to application of textured finish or primer.

Note:     Retaining walls must be properly waterproofed before application of Sto products to the exterior face of the retaining wall. Absolutely no exceptions.
Note:     Parapets and sills must be sloped to shed water. Terminations at windows or at roofing material must be properly flashed and/or caulked to prevent water infiltration behind the waterproofing application.
G.         After preparation and repair of all surfaces the textured finish application may begin.  Where a primer
            is used apply with brush, roller or proper spray equipment to the substrate and allow to dry thoroughly 
            before applying the textured finish coating.  The textured finish shall be applied by spraying or
            troweling with a stainless steel trowel.  General rules for application of finish are as follows:
            a.  Avoid application in direct sunlight.
            b.  Apply finish in a continuous application, always working to a wet edge.
            c.  Weather conditions affect application and drying time.  Hot or dry conditions limit working time and
                 accelerate drying and may require adjustments in the scheduling of work to achieve desired results; 
                 cool or damp conditions extend working time and retard drying and may require added measures of
                 protection against wind, dust, dirt, rain and freezing.
            d. “R” (rilled texture) finishes must be floated with a plastic trowel to achieve their rilled texture.
            e.   Avoid installing separate batches of finish side-by-side.
            f.   Avoid application over irregular surfaces, especially with smaller aggregate finishes, which will not 
                 hide deviations in the plane of the surface.
*The holder of the Sto Certificate has been instructed by approved Sto Instructors in the correct application and
handling of specific Sto Materials.  However, the applicator is an independent contractor and Sto Corp. cannot control the manner of his/her work nor can it guarantee that the applicator will correctly apply and handle all Sto Materials. 

​

Water Leak Identification and Testing for Windows and Doors

Water leakage through windows / doors, stucco or roofing systems can be frustrating due to the circuitous route that water will travel. Identifying the area of moisture infiltration can be methodically approached to insure the proper area is identified and the appropriate fix accomplished. Considering that leakage problems in New Mexico are mostly related to stucco, we offer repair solutions specifically for the architecture in this area.

The natural reaction by the untrained person is to identify the leaking area as the local area of entry on the inside of the building, and assume it correlates directly through the wall to the exterior. This approach generally does not yield an accurate diagnosis and leads one to believe that a window or crack in the stucco is directly responsible for the problem, when in reality it may be a roofing problem or leakage in a completely different area. 

In the case of a leaky window or a vertical crack in the stucco, it is believed in some professional circles, that water is actually sucked or drawn into the house, rather than being driven through the wall by low pressure inside the home. Although there are conditions when wind driven rain is forced into and through a breach in the wall or window.

The sixty-four thousand-dollar question is always, where is the leak occurring? Once the leakage area is identified, a proper procedure for repair is always available, sometimes very economically and other times more expensively.

Testing is the first step to identify the area of moisture infiltration. Much of the testing procedure was adopted from the book, “Idiot’s Guide To Water Testing Windows” by Daniel Urroz. One can purchase this book by calling 1-800-655-9349 or by the Internet at www.buildersbasement.com.  For homeowners that are willing to dedicate a few hours, Urroz’s book is a wealth of information for leak identification.  At Reule Sun Corporation, we agree with much of the testing procedure and offer amendments to the testing for accelerated results. It is important to conduct the testing from the bottom to the top of the wall. The order of the following testing is important to isolate the leakage.

Test procedure #1: The object of this test is to test the window proper while isolating the stucco and the window to stucco interface out of the loop.  Shut and latch the window. Using duct tape and 3m masking film or landscaping plastic, tape the plastic at the edge of the window frame and lap the plastic onto the stucco two to three feet. Tape the outside edge of the plastic onto the stucco.  Strips of plastic can be used, starting horizontally at the windowsill, sides and top, making sure to overlap the sheets like shingles of a roof. Tape all of the overlapped plastic joints to create a seal. Make sure to keep the plastic film flat and avoid wrinkles in the film while applying the tape; so as to create a watertight seal. Apply a second layer of tape over the first layer and onto the stucco around the total perimeter to insure adhesion.  Spray the entire window, assimilating a heavy rain for 20 minutes. Observe the interior of window and localized areas, around, under and along the baseboard, for moisture infiltration. Wipe off and dry window and frame. 

Test procedure #2: The object of this test is to isolate the window out of the loop and focus the test on the transition of the stucco to the window frame. Shut and latch the window. Using duct tape and 3m masking film or landscaping plastic, tape the plastic film onto the frame of the window, around the entire perimeter, right up to the edge were the stucco meets the window frame and cover over the entire window. Make sure to keep the plastic film flat and avoid wrinkles in the film while applying the tape; so as to create a watertight seal. About one inch of contact of the duct tape onto the window frame is adequate. With a water hose turned on with moderate pressure, start flooding water at the bottom of the windowsill and move the hose along the sill for ten minutes.  Observe the interior of windowsill for moisture infiltration.  If moisture is observed, tape a two-foot flap of plastic onto the bottom of the windowsill to span from the windowsill and over the stucco. Continue the test individually on each side of the window for twenty minutes each, and next the top of the window for 30 minutes.  Urroz offers a great tip by utilizing a strip of plywood with a clamp to hold the hose in place. Continue with the observation on the inside for moisture infiltration. Next the water can be run onto the stucco wall above the window for 20 minutes, while paying particular attention to flood any areas of the stucco that show cracks.  Again, observe the interior for moisture infiltration.  It is important to conduct each step of the test methodically and by the times prescribed above so as to find fault or eliminate each individual area.  If no moisture infiltration is evident, proceed to the next step.

Additional Procedure: If no moisture infiltration is evident in either of the above tests, an additional step can be performed to insure absolute results for the testing. By creating a negative pressure on the inside of the window, it can aid todraw the moisture inside. Utilizing the previously described plastic and masking materials, mask over the entire opening at the inside of the window and onto the interior sheet-rock or plaster wall, making sure that the entire window is encapsulated behind the plastic.  Apply a second layer of tape onto the wall and just overlapping the existing tape to insure adhesion. Utilizing a vacuum cleaner hose, cut a hole in the plastic, place the vacuum hose through the hole and tape to seal the hose to the plastic.  Turn on the vacuum and conduct the above tests. If there is no moisture infiltration, you can safely conclude that the tested areas are leak resistant. Only a slight bit of vacuum is required. It is best if a restriction in the hose can be made so as to create a realistic negative pressure on the inside.  If a “Fan Door” is available for testing, a 15 Pascal pressure reduction to the interior of the building is adequate to conduct testing.

Test procedure #3: The object of this test is to focus the test to a flat roof parapet cap.  Once the above Tests are conducted and it is proven that there is no leakage, then testing of the parapet can take place.  The procedure is to flood the top of the parapet for twenty minutes, vertically above the area of infiltration.  Considering that water can easily migrate for ten feet or more, the flooding of the parapet should occur laterally ten feet on either side of the vertical alignment with the leak.  Care should be taken to keep the water off of the roof in this first step.  If no water infiltration occurs, then the backside of the parapet should be flooded.  Please note that by this second step, while flooding the backside of the parapet, water will flood onto the roof as well.  If water infiltrates into the wall, it is inconclusive whether the water is infiltrating into the parapet or by a leak in the roof. 

The fix: Fixes for water leakage can be as simple as utilizing a caulking product, to more elaborate sealing methods and finishing of the stucco or synthetic stucco products.  If it is diagnosed that the window is leaking, with a top grade window, generally the fix is straightforward and involves replacement of weather-stripping or caulking. With wood or aluminum clad windows, it may be necessary to replace a defective sash or in extreme cases, the entire window.  If the transition of the stucco to the window is leaking, the fix can involve more than just caulking and usually requires that the window be removed and reinstalled properly or replaced with a new window, if required.  For problems relating to your specific window(s) brand, contact the manufacturer representative, which is customarily listed on the internet. If you suspect the roofing is causing the problem, contact a qualified roofer of your choice such as Rome at Cornerstone Roofing at 505-842-1113 or Mike at A 2 Z Roofing at 505-319-2670 for a free evaluation and consultation. For problems relating to your stucco or synthetic stucco product, or if you choose to upgrade to a high quality window or door product such as Andersen Windows and Doors, PlyGem PremiumVinyl Windows or beautiful Semco Wood Aluminum Clad windows and doors, please contact Reule Sun Corporation at 505-345-3200 for a free evaluation and consultation.

Misconceptions of the Common Crack

Read this article detailing misconceptions about cracks in stucco.