Addendum to discussion about bonding agents

 

 

The more I learn about the uses of glues the more I am finding how tricky they can be. We discussed in the last installment of the proper uses of different types of glue. Some glues are strictly admixtures and some are particularly suited for the receiving surface. Problems typically arise with respect to weather and moisture retention. We discussed last time that acrylic admixtures should slow the set time down thereby making the cement material denser. This is not the case when it is hot. However, in temperatures over about 85 degrees F we find that the modified material spikes with the introduction of acrylic. That is, the material will set the mix more quickly when it is hot. With respect to PVA and EVA surface preparations we are finding some of the same inconsistencies. As plasterers and support personnel, we constantly look for new ways to improve the outcome of our products and finishes. I was recently on a job in Santa Barbara where the plasterer was re-scrubbing an existing Santa Barbara Finish (smooth) parameter wall. Since a smooth coat was already on the wall (unpainted) the plastering contractor felt it prudent to glue the wall before scratching in the first coat of smooth stucco. As it was a warm sunny day the glue appeared dry and the scratch coat was applied. As the crew doubled back over blisters began to appear. All the discussions that I have had about blisters are there is too much moisture in the material and the second coat breaks the set and bond of the first coat. What I have found since is that judging the readiness of the first coat when there is glue on the wall is tricky. It appears dry but in reality the glue is holding moisture on the inside of the first coat. Some plasterers always wait over night following the application of glue to make sure it is completely dry. These bonders all re-emulsify as the wet mud is introduced over the top. The difference is that a PVA will continue to re- emulsify for up to a week (or more depending on weather) and an EVA will only re-emulsify for 72 hours. The distinction is important and, at the same time, very tricky. The weight of the stucco can pull itself off the wall if the glue re-emulsifies following application. So we want the glue to “wet up” as we apply the stucco to insure a chemical bond, but we want it to cure before an appreciable amount of moisture is introduced. Another problem is when a bonding agent is put on the wall it will again hold moisture. This time it is after both coats of smooth (Santa Barbara Finish) is applied and the material has had its final “hard trowling”. The material looks great but since there is moisture present it continues to cure over night and the moisture naturally wicks out and hydrates. This leaves “checking” in these areas. This is also known as “spider web cracking,” “crazing,” or “shrinkage cracks.” Some of these are considered normal and part of the finish as it is virtually impossible to eliminate these small cracks.

 

Consider also that if there is suction (as with the aforementioned re-stucco of an existing smooth wall) should we use glue? In this case we are eliminating the suction bond in lieu of a chemical bond. I have always been partial to a suction bond whenever we can get it. As I interviewed more mechanics about this issue I noticed that some have found (receiving surface type) bonding agents to be tricky enough to quit using them. These guys have gone to using a polymer modified base coat similar to Basex to base out the wall. This is a way to introduce a polymer modified cement coating to bond to the existing wall and still have suction and key to bond the finish coat.  

 

When I discuss polymer modified cements, base coats and glues, I usually find myself voicing one of my favorite adages: “for every solution comes its own set of problems; we just hope the solution is better than the problems they bring!”  We are all “big boys” when it comes to plastering and construction and know that we picked a trade that is very difficult. We get blamed for every crack and imperfection in the finish coat and sometimes have no answers why. As we try to elevate the industry by using new products and techniques we have to remind ourselves that it is worth the effort. At least we are out there trying. Who knows? Maybe we will find a cementitious finish that someday will have all the functionality we want with none of the present problems. Until then, let’s just keep thinking!

Shuttle Endeavor Stages Flyover of Local Stucco Business

 

To commemorate the 50^th anniversary of Merlex Stucco of Orange, NASA today staged a flyover of the Space Shuttle Endeavor over the Merlex facility.  Although no Merlex products were used on the Shuttle, President Nick Brown says “we have some terrific Venetian plaster finishes that go on real thin and would have really classed up the cockpit.”  Crossing over the Merlex plant at approximately 12:30 pm today, the Shuttle approached from the North, flew over Knott’s Berry Farm and Disneyland, across the Santa Ana River to the east, and then banked right toward its ultimate destination, LAX.  Often quoted as saying “It’s not rocket science” when talking about stucco, the Merlex team welcomes any future involvement with the U.S. space program.

Real Stucco vs. Synthetic Stucco

Many people are confused by what the difference is between real cement based stucco and synthetic stucco. In the 1970’s we started hearing about stucco that didn’t crack and had more color consistency than the stucco we were using. Then the word EIFS (Exterior Insulation Finish System) was thrown around and the confusion really started. EIFS is for energy efficiency using foam boards or other products to achieve better insulation values and is a whole other discussion. Much can be learned on line regarding EIFS Systems. One of the problems is that we have so many names for synthetic stucco such as; Acrylic Stucco, Synthetic Stucco, Plaster Finish, and manufacturer names such as; MX Acrylic, Dryvit, Sto, Synergy, Thoro etc. Here is the difference:

Synthetic Stucco is made from acrylic resins and is very similar to paint. They have an aggregate added to replicate the look of stucco without some of the inherent problems of real cement stucco. Different size sands are used to achieve different finishes as traditional stucco uses different size aggregates. Once on the wall it would be difficult for anyone to tell the difference between Acrylic Stucco and a painted cement stucco wall. The key here is painted. It is fairly easy to tell the difference between real and synthetic, if not painted. Even though the products are supposed to be similar when they are installed they are worlds apart in physical make up and functionality. Real Stucco uses natural materials and is cement and lime based. Synthetic stucco is acrylic resin based using no cement or lime. The similarity is the sand or aggregate used. The functional aspect is also important. Synthetic stucco stops water from coming into the wall and are either characterized as water proof or at least water resistant. Cement Stucco typically dries hard enough to keep water out but the idea is not to necessarily keep water out of the stucco. More importantly it can penetrate the stucco and then naturally wick out and dry by being highly vapor permeable. Synthetic Stucco can keep and hold moisture if it can find a way in. This is usually through the windows, doors, or roof lines. Because of water related issues the manufacturers have tried to use co-polymer resins that have more vapor permeability than earlier synthetic stuccoes. Cement Stucco is very rigid and is susceptible to cracking. This has been by far the number one problem associated with stucco.  Cracks are caused by many variables all related to movement and can be read about in earlier Blogs or on line. Stucco also tends to dry differentially by how long the moisture stays in the wall. Cement Stucco typically is darker if it dries slowly and lighter if it dries quickly. In hot, dry, or windy conditions the entire building can be lighter in color than intended; conversely in cloudy, moist, or wet conditions the entire building can be darker than intended. In addition, walls can dry differently just based on shading. The north side of the house can dry darker than the south side. Even shading from plank, trees, or other structures can telegraph on to a wall and cause discoloration.   Synthetic Stucco was introduced to solve these problems and for the most part they did. Since Synthetic Stucco is a lot like paint it dries more evenly. Because of the nature of the resin it moves more than cement stucco and is not as susceptible to cracking. Keep in mind nowhere did I say “solve or eliminate” the problems. Problems and their manifestation are all a result of degrees - how much movement, how much water intrusion. The other question was of course cost. Price was always the motivation of using traditional cement stucco. It is relatively inexpensive. Synthetic Stucco changed that and made the cost significantly higher. Still, when stacked up against other claddings, both these materials are still very affordable. So let’s go through and recap these products:

Synthetic Stucco

1.       Made of Co-polymer Resin

2.       Uses sand or other aggregate to achieve the look of Cement Stucco

3.       Resistant to water

4.       Crack resistant

5.       Color fast

6.       Comes  wet in pails

7.       Spread with an acrylic trowel

8.       More appropriate for dark colors

9.       Able to have smooth to very heavy textures

10.   More expensive than cement stucco

11.   Can be used over brown coat or in EIFS (Exterior Insulation Finish System)

Traditional Cement Stucco

1.       Made of Cement and Lime

2.       Uses different size sand to achieve different finishes

3.       Highly vapor permeable

4.       Comes dry in bags

5.       Spread with steel trowels and floats

6.       More of a “natural look”

7.       Less expensive

8.       Can be used over brown coat, continuous insulation systems, base and mesh.

As you can see there are more differences than first meet the eye when making a decision which product to use. Cost is a factor and how the materials function and ultimately look are certainly things that need to be addressed. Do your research, look at the budget, and make the right decision based on your design needs and expectations of all involved.

SEALERS FOR CEMENTITIOUS SURFACES

MERLEX STUCCO NOMINATED FOR MOST SUSTAINABLE EXTERIOR FINISH ON             GREEN THINKER NETWORK 



There are many sealers on the market. Most are to protect the surface from water or moisture intrusion. There are sealers that are designed to enhance the beauty of the surface or add gloss or a “wet look”. Sealers can be categorized as surface or penetrating. Surface sealers are usually silicone based and last from as little as a few months to a few years. The reason is that silicone is a larger molecule and therefore sits closer to the surface. Since UV light is what attacks these sealers then the larger molecule silicones will break down first. Penetrating sealers are usually silane and or siloxane based. This is a smaller molecule and therefore penetrates further into the surface before forming the hydrophobic barrier.  Silicones are usually less expensive than silanes so how long you want the sealer to last is important question. The substrate is the next most important variable. How porous is the material? This will determine how deep a penetrating sealer will go. This is a two edged sword, the material will last longer as it penetrates deeper but it won’t seal the surface from staining. The primary function of a good penetrating sealer is to keep moisture out of the wall cavity. This is where the water can do the most damage. It can find a way into our homes damaging drywall and carpet but what we don’t see is usually worse. Degradation of wood framing, damaging electrical outlets and shorts and growing of molds are just a few examples of damage water can do as it enters the wall space. We must be aware however; that penetrants are just that, they will not protect the surface from staining unless built up to the surface with subsequent coats.  The proper way to put on penetrating sealers is to make sure that new concrete, masonry or stucco is cured and “thirsty” enough to accept the chemical. Since the chemical is now carried by water this is pretty easy to test. The literature usually says to wait the initial 28 day cure period before application. The problem with this is that your wall can get badly stained in 28 days. My advice is to gauge the weather against how dry or “thirsty” your substrate is and then make your own decision as to when to apply the sealer. These sealers need to form a barrier so there needs to be enough material put on to make that barrier. This usually means we put on a “flood coat” and then brush off any excess material. From a chemical engineering perspective the exact proper way is to apply a very light “fog coat” of material to “open the capillaries” of the wall. Then come back immediately and flood the surface to insure the wall accepts as much material as possible. Most often people just use a pump up “bug sprayer” and fill the wall with material until it runs and then back roll or brush off the excess. There is a very important caveat here though, when it is hot dry or windy and when doing flat surfaces it is critical to get the right amount of sealer on. If there is too much material and the substrate cannot accept the chemical and it will be deposited on the surface. This will result in a residual sticky material left on the surface to catch dirt, leaves, foot prints or whatever blows by. So try to do the job in the morning before the sun is too hot and don’t use these sealers when it is windy for this reason and you won’t get an even application. If you find that there is residual material left on any surface you can cut it off with a solvent. Paint thinner or any other solvent can be put on a rag and cut the material off the surface. Don’t worry, the rest of the material will still be in the wall as long as you don’t let the solvent penetrate. Just use it to wipe off the excess chemical without having it drip off the rag. It will evaporate very quickly and be gone leaving your sealer intact. Remember to cover all windows and frames as these penetrants can etch glass. Please read all the safety instructions before use. Think about the material you are putting the sealer on. Is it a flashed brick with very little suction? Then the material will go in very slowly or not at all. Very porous products like a Concrete Masonry Unit (concrete block) are very porous and will therefore use a lot of product. Merlex makes a penetrating sealer call Micro-Seal II that is less expensive than any other penetrating sealers I have found. It is a great product and is warranted for 10 years!  The literature will show how much sealer will cover different materials. Logic dictates that the more “open” the surface the more material will go in and the further it will go in. The less “open” the substrate the less the material will go in and will therefore go further in terms of coverage. You can use these products on brick, block, stone, concrete, stucco or any other cementitious substrate. I have found over the years that silicones are used because people don’t know about silanes. Why would you use a sealer that will last 3 years at best when you can use penetrants lasting 10 years? The price difference is not that much. I guess if it is model complex of homes or a case where a year of protection is fine then the less expensive silicone will fill the bill. I talk mostly to homeowners that are doing their own homes and want maximum protection for the longest period. Go with a good penetrating sealer and take all the precautions talked about here and you will protect your surfaces without having to reapply every few years.

SHOWER FINISH

I’m always so surprised when I talk to builders and architects about shower stucco. It seems it is very hard to find and not widely known. Shower Finish was first made many years ago as a substrate for tile or in locker rooms and industrial kitchens. It was an effective way of stopping water; the concept was to have a durable waterproof material to paint or tile over.  Through the years people have found the product on our website and it is now most common as a “finished product”. I think people are tired of cleaning ugly grout in tile, and marble and granite are very expensive. With the resurgence of contemporary and “loft style” homes in the city the cement look inside has gotten very popular. Of course, some people add color to shower finish to match existing counter tops and décor. Super Shower Finish is a polymerized cementitious coating that can go over scratch and brown (typical underlayment for tile). It can also be easily retrofitted to make a bath into a shower or just upgrade existing. As with any other cement product there needs to be some suction for bond. A base coat over a cement board is typical and works well. When I did my daughters house we screwed Durock (USG) to the studs (3x5 sheets at 3/8 or ½ inch thick) and meshed the joints (2 inch drywall mesh works fine). Then a base coat of a polymer modified cement for extra strength (like Merlex Basex) and then two coats of Super Shower Finish. This is typically troweled smooth. The material can be carried out into the entire bathroom if desired. Be advised that when the material is wet you can see streaks as the water tends to absorb a small way by not evenly. When it dries it gets pretty consistent again. Also, as any other smooth cement based stucco expect some color mottling and variation. Of course, this is what most people want.

Any cement material is extremely high Ph so it is a natural biocide. Soap scum doesn’t build up and it’s as easy to clean as any smooth material. There are no joints or areas that require scrubbing. People often ask if a sealer is recommended over the Super Shower Finish. I actually tried that myself just to make sure it was water tight. I used MicroSeal II but couldn’t get it to go in. The answer is: “if it makes you feel better to seal it go ahead”. It works just fine without it.

I am convinced that if more people knew about this it would be used extensively. The material lasts for decades and is virtually maintenance free. Color is open to the imagination as some people add multiple “blend over” colors and get real creative. There are bathrooms that are now part of the “outside” that are carried into a private garden or courtyard. This works great as it can match the existing exterior stucco seamlessly. Design professionals and architects are really excited about using this product and I have been working with some designers in New York that just love it. It certainly is a different look so be sure it’s what you want. Most people do their own color. Although, Merlex will make matches and provide the color as well. It is highly recommended to experiment with the color and get the approval of the customer by using a mock-up before proceeding.

There is a frequently asked questions technical sheet at the Merlex site so if you’re interested in this product look at the Technical Data Sheet on Super Shower Finish and the FAQ.

Good Luck!!!

What’s Philosophy Got to Do with Construction?

 I recently visited the Green Idea House in Hermosa Beach (http://www.greenideahouse.com/), which will be a beautiful contemporary custom home that is net zero energy.  There are several categories of zero-energy houses, but this one is “net zero”, meaning that balanced out through the year, the home will use no more energy than it generates.  It may draw off the grid during peak times, but will return that much and more back to the grid over the course of the year.

To get to “net zero”, they are building a tight building envelope with energy-efficient windows, blown-in cellulose insulation, an efficient heat pump water heater, and plenty of PV cells on the roof.  This would be enough to make the project remarkable in this region.  But these homeowners have taken the project much farther, to the point of making it an intellectual and philosophical challenge.

The Fortunatos, owners of the home, are blogging about the experience of building their home this way.  Perhaps because of the full disclosure of every decision they make, they are taking the time to dig deeply into the pros and cons of each design decision and material choice. They would like to help others think about how decisions they make for their home should be dictated by their specific lifestyle. And there are some eye-opening conclusions on their website for you to consider in building your own home.

For instance, installing tankless water heaters and solar thermal panels has become a common practice in green home building.  Instead, the family chose a multi-tank solution that first pre-conditions the city water to ambient temperature, which at the beach is quite often 75 degrees, a savings of 20 degrees worth of energy use.  Then they utilize a new technology heat pump that has efficiencies far in excess of traditional gas burners used in tank and tankless heaters.  While tankless water heaters have widespread advantages in certain situations, there are no one-size-fits-all solutions in green building.  The owners thought about water heating in terms of how best to support their lifestyle and generate return on investment; in their case – 3 people who are often out of town travelling – a solar thermal system and tankless water heater were not the answer.

The building design also takes into account orientation to the sun to keep sun out in cooling periods and welcome it in during heating periods.  The southern exposure is the culmination of this philosophical debate.  Using quantitative models, they arrived at a 5-foot overhang over the windows on the front of the house, carefully calculated to shade the building from the sun in summer (high up in the sky) and to allow the sun to heat a thermal mass wall in the master bedroom during winter (when the sun is low in the sky).  Decisions like this can save significant amounts of energy, and are modeled by Energy Soft when an energy consultant evaluates a project.  Every window is entered into the model with a specific compass orientation and overhang dimensions, so that passive energy use can be considered.

The homeowners are also looking deeply into the insulation design on their project.  Once the solar arrays had been specified and they knew the energy their home would produce, they could design the building envelope to release only a known amount of energy.  They settled on blown-in cellulose insulation between the framing members (many of which are reused 2x4s), for an R-value of about 13.  Rather than install foam on the exterior of the framing, commonly known as Continuous Insulation or CI, they determined that vapor permeability of wall systems is a desirable feature for air quality and mold resistance.  Their search for an energy efficient alternative to foam insulation led them to fiber board, a natural vapor-permeable material that adds an R-value of 2.6 for every inch of thickness.  Together with the blown-in insulation, their wall systems achieve an insulation value sufficient to realize their goal of “net zero”, together with all the other good decisions they have made throughout the house.

Next they had to choose an exterior cladding system that is attractive and protects the building from the elements.  They determined early on that they wanted to incorporate recycled content into their project, while minimizing embodied energy (the energy used to produce the materials in their home) and minimizing energy loss through the walls.  They are using metal panels on parts of the building, and plaster elsewhere.  The plaster will incorporate recycled content from locally-sourced recycled concrete aggregate and flyash.  The flyash question is a debate in and of itself, with questions of heavy metals, coal-fired power plants, and long-term maintenance to consider.  As with every other decision on the house, the Fortunatos considered all the angles in deciding whether to use materials that incorporate flyash and divert it from landfills.

Build Smart Group advised the owners on plaster material decisions, including fiber-reinforced base coats with recycled content, color coat stucco finishes based on recycled aggregates, and lime plasters with lower embodied energy than cement-based alternatives (and stunning good looks).  Merlex Stucco’s website is a good source of inspiration in this area http://www.merlex.com/sustainable_stucco_how_to.htm.

 Interior surfaces will take indoor air quality into account, which is one of the easiest areas to build green today, thanks to the tireless R&D work by the nation’s paint companies.  Plaster products can also produce zero VOC performance with added aesthetics, and some even claim to actively clean the air.  Indoor climate control was also a consideration that led to selection of National Gypsum’s brand new phase change drywall.  These drywall panels contain tiny wax beads that change phases right around room temperature.  During the daytime, the encapsulated wax material melts, which absorbs heat from the indoor space.  As the liquid cools down along with the house in the evening, the wax returns to solid form and releases heat.  In this manner, the phase-change materials of PCMs act to regulate room temperature and reduce heating and cooling load on the HVAC system.  The Green Idea House calculates that master bedroom energy use will be cut in half through the use of these PCM drywall panels!

This project should serve as an inspiration to all green-minded homeowners to carefully consider how their new home fits their lifestyle.  Rather than leaving the key decisions up to design professionals working in a vacuum, owners should fully inform their design teams of their values and lifestyle and what green means to them.  After all, for those blessed with the resources to create the home of their dreams, a home should say “This is our home.  This is who we are.”

Merlex Stucco is continually improving its product line of natural stucco products to add products offering (1) energy efficiency; (2) recycled content; (3) local sourcing; and (4) reduced embodied energy. Products to be included on the Green Idea House Case Study include 33% Recycled Stucco (based on recycled concrete aggregate), and Vero Antiqua lime plaster (from Merlex's Vero Venetian plaster subsidiary), which has 28% lower embodied energy than cement stucco and incorporates 65% recycled marble aggregate. Merlex & Vero are pleased to support the Fortunatos, who are kindred spirits in their quest to find the most sustainable choices in products that fit their lifestyle.

BONDERS

There are three main types of glues used in the construction industry. Concrete Glues (Poly Vinyl Acetates), high end bonding agents (Ethyl Vinyl Acetates), and Acrylics. I am convinced these products are used interchangeably and incorrectly most of the time. I have seen contractors putting acrylics on the wall to bond mud or stucco. I have seen them pour Concrete glue in the mixer to modify the mix and add strength. These guys have been using these products wrong for so long that they are convinced they are right! I have called these guys on this many times and the reaction is the same: “I have been doing this for 20 years”! My gut is that this actually does work to some degree. The logical conclusion is that these are all glues and would react whether in the mix or on the wall. However, there is a right way to do things. Acrylics are always admixtures. They modify and strengthen the material they are added to. Acrylics allow the cement in brown coat, stucco, thin set, or any other cement based product to cure longer and therefore denser. The closer (denser) the molecules the harder (higher Psi) and also the better water resistance you will get. Acrylic admixtures can react differently depending on the weather. Guys used to tell me they didn’t like using acrylics because they “spike” the mud. That is, make it set-up more quickly. My teacher told me it made the material cure longer and therefore stronger and better. So which is it? I called my guru and he said the answer is both! When the weather is over about 85°F to 90°F acrylics can set the material more quickly. This is why we recommend using PVA or EVA on the wall instead. The other truth about acrylics is that the price difference between them has to do with percentage of solids. Some companies add more water than others. So it holds true here that “you get what you pay for”. Some very inexpensive acrylics probably have solids in the low teens and the good ones like Merlex Acrylex are in the high 20% to low 30%. This can be triple the amount of actual chemical that does the job!

PVA’s and EVA’s are another source of confusion. These always go on the receiving surface. They are used on the wall if there is a “bond issue”. That is, if there is something on the wall that inhibits suction. Suction is what causes subsequent material to bond to the last material. As in stucco to brown coat or stucco over stucco. So if there is a bond-breaker like paint, sealers, oil, dirt, synthetic stucco, or any other material that inhibits bond then glue should be applied to the surface. The two main characteristic differences are PVA’s re-emulsify. This means they can become a liquid again after drying. That can be good if you are coming back later to apply the coating or it can be bad if you apply the coating and it rains and the coating slides off the wall! EVA’s do not re-emulsify and are best to use if there is any chance of rain or moisture within 72 hours. Again these chemicals are cut with water and the percentage of solids can be very low. Be careful of inexpensive glues and best to trust name brands. Contractors seem to love Weld-Crete®. It is a great product and very high in solids. Weld-Crete is a PVA and will re-emulsify. Mighty Bond from Merlex is a high solid PVA and the price is in the mid range. Merlex also makes an EVA called Superhold that is the best bonder on the market. It has a blue tint to it so you can see where it is (or isn’t) on the wall. It is towards the high end in price but is high in solids and is the right chemical to use outside.

Soka University - Laguna Niguel, CA

So what is the answer? Is it best to use acrylic in the mix to insure bond or put an EVA on the wall or both? The answer is both. The acrylic in the mix will stick to the EVA on the wall for a chemical bond in lieu of a suction bond. You can get away with either but the acrylic must be dispersed properly in the mix, and the bonding agent must be on every square inch of the wall to bond. With both materials there is that much greater probability for success.

I hope that this can help clear up the use (mis-use) of bonding agents in the field. Reality is that whomever reading this is NOT the plastering contractor. More likely it is a homeowner that will have the onerous task of telling the stucco guy his job…. This never seems to go well!