The "stucco" that is normally used for interior application and is made up of "joint compound". The way it is installed gives you the appearance of stucco. In you case a "mortar" of some type should be used to adhere to the block. I would consult with Lowes or Home Depot to find a compatible product with the right "binding qualities". You can trowel the material to the block. It may be necessary to use "dry-lock" if using in an area where moisture is present.
Key to the whole project is the preparation:
Whatever you decide to do you must first prepare the concrete for the product used to adhere. A few tips...
Cost-effective, sturdy, versatile - it's no wonder use of concrete in commercial and residential construction is increasing. Statistics on the U.S. cement industry show that despite a softened construction market, Portland and masonry cement consumption combined rose slightly in the year 2000 for the 10th consecutive year.* Total world cement production increased by 61 million metric tons in 1999, the most recent year for which such data was available.* And comparisons of cement-to-construction dollar measures suggest that industry promotion continues to have a positive impact on cement usage in the U.S.*
One reason for the continued increase in concrete use is that architects and developers are discovering that this reliable old stand-by is ideal for far more than walls and floors. With the right mix of skill and knowledge, concrete can be intricately textured, colored and patterned for a multitude of strikingly beautiful uses, from gracious lobbies, pool surrounds and patios to handsome pillars, columns and even countertops.
Like a hand-in-glove, concrete and coatings belong together. Whether the function of the concrete coating is decorative or protective - or a combination of both - coatings and decorative finishes can enhance concrete surfaces in ways that impart style, improve longevity and increase client satisfaction with the project - along the way transforming a dull, colorless expanse into a noteworthy design element.
Dispelling the Myths
Smart contractors, with the help of an ever-growing selection of concrete finishing products, are taking advantage of this increased awareness of concrete's aesthetic possibilities. As a result, they are expanding their markets by learning the methods and techniques to deliver these exciting new looks. But what exactly do contractors need to know about concrete coatings?
With all of the new products and techniques available to help contractors achieved desired effects, some confusion about coating characteristics and attributes is inevitable.
Myth #1 : All the various products and processes available today to colorize and detail concrete are "coatings."
From acid-etch stains and color admixtures to concrete etching and overlays, there are numerous ways to enhance the appearance of concrete surfaces. But many of these are not actually concrete "coatings." Acid, polymer and other chemical stains, for example, are not paints or coatings, but are, rather a coloring process that initiates a chemical reaction with a cementitious surface.
Water-based concrete stains, typically composed of acrylic resins -- while technically not coatings -- behave more like coating products because they do not react chemically with cementitious materials. Instead, these products penetrate deeply into the concrete surface, providing colorization and protection against harmful elements to both vertical and horizontal surfaces.
Water-based acrylics resist fading and abrasion, and they may be applied using stencil designs to create faux brick and geometric effects. Easier to apply than chemically reactive stains, water-based acrylics clean up with soap and water. Another advantage is compliance with even the strictest air quality regulations due to their very low VOC (volatile organic compound) content.
Myth # XXXXX: Coatings, by their nature, bridge the porous surface of concrete, trapping moisture already present that seeks to escape through the surface and setting the coating up for failure.
Not necessarily. Coatings do bridge porous surfaces, in the process protecting concrete and masonry surfaces from water penetration. But a number of newer concrete coatings are available that are highly permeable from the substrate side. There are new elastomeric coatings, for example, that are as easy to apply as paint, but which allow moisture vapor from within the concrete to escape. This quality virtually eliminates the problems of blistering, peeling and delamination associated with most concrete coating failures.
Elastomeric concrete coatings apply to a thick, elastic film that enhances concrete surfaces by providing uniformity while concealing hairline cracks, patches and other irregularities. At the same time, these coatings improve concrete longevity by providing protection from wind-driven rain, even in coastal or severe-weather environments. They are available in a wide range of colors and also may be tintable.
Textured elastomeric coatings provide these same benefits, while offering the advantage of an imperfection-camouflaging, uniform finish that adds visual interest to otherwise ordinary pre-cast panels or concrete block surfaces. Such coatings are available in different textures, plus a wide variety of factory-tint or store-tint custom colors, so enhancement possibilities are numerous. What's more, the choice of textures makes it possible to easily match new areas to existing textured surfaces to deliver a clean, consistent look across an exterior expanse.
Myth #3: Concrete must cure for at least 30 days before coating
While many coating products cannot be applied to "hot" masonry surfaces (NOTE: always carefully read and follow the individual manufacturer's instructions) some primers and topcoats can be used after just seven days of curing. These systems may provide an ideal solution to schedule conflicts resulting from weather or other job-related delays, or help make possible a fast-track construction schedule.
Look for primers and topcoats that can be used successfully on substrates with surface pH levels from 6-13. These systems are available in white as well as a wide range of pastel and deep-base shades.
Myth #4: Concrete block fillers are unnecessary, heavy and difficult to apply.
What better way to prepare a rough, uneven profile for a beautiful topcoat or decorative finish than using concrete block surfacer? These coatings dramatically enhance a concrete surface by providing a stable, uniform foundation for finishing by filling pores, voids and pinholes - often in just one pass. But unlike the block fillers of old, new, lightweight concrete block surfacers are available today that backroll faster and with less effort, so they save on application time. These products may weigh as much as 30 percent less than traditional block fillers. They are also useful for building a solid barrier between topcoats and the substrate, preventing pH burns even over freshly cured mortar.
Myth # XXXXX: Chalky concrete cannot be coated.
While chalking concrete should not be directly topcoated, it certainly can be prepared for topcoating through the use of concrete conditioner products. These coatings penetrate deeply into masonry substrates to secure chalky surfaces and create a stable base for long lasting finish coats. On new construction, they may be used as a penetrating sealer for surfaces that include 7-day- cured concrete. An added advantage of concrete conditioner use is prevention of topcoat delamination and alkali burn - even on concrete substrates with pH levels as high as 13. These coatings can serve as an economical alternative to primers and are particularly useful on rehab projects where the existing topcoat has deteriorated over time.
A Word About Surface Preparation
While conditioners can go a long way toward preparing a concrete surface for topcoating, before any coating is applied, some simple steps should be taken to assure a proper bond. Most coating failures occur not because of improper coating application, but because of inadequate surface preparation. For a coating to properly adhere to a concrete surface, the surface must be clean, dry, dull, sound, and free of surface defects such as cracks or spalling. These areas should be repaired using the appropriate patching compounds. The surface to be coated should have a slightly rough profile - approximately equivalent to a piece of 120-grit sandpaper.
Be sure to clean the concrete to remove any grease, oil, dirt, old paint or other contaminants, using one of the methods recommended by the manufacturer of the coatings you will be using for the job. It's important that the surface is properly prepared so that it is compatible with and receptive to the specific coatings you plan to apply, so be sure to check your tech data pages. Pebble blasting, power washing, acid etching or cleaning with a commercial concrete cleaning agent are among the methods that may be recommended.
* Portland Cement Association U.S Cement Industry Fact Sheet 2001 Edition
Before coating, a concrete surface should be:
Hi Bob; Having only been a hod tender myself I decided to consult the oracle. Hes a 83 yr old Italian grouch that gets to the job site at 6:45 every day. He opens the shed (roll off) and gets his seat out. From there he conducts operations like no other foreman I have ever seen. So I would think that he might have some stucco experience behind his advice.
the first thing he said after I asked him the best way to do it was "hire a (expletive) hispanic to do it" (he was not politically correct at all). He then gave this advice-
1) get all the paint off if there is any.
2) repair any cracks or voids.
3) buy a good brand of color coat. DONT GET CHEAP!
4) prep EVERYTHING before you start to mix mud.
5) dig all the dirt away from the base to at least 4 inches below the point you want the stucco to end.
6) get a 5 gallon bucket and a 'Tom Sawyer' brush and tell your helper to mix 1/4 gallon of AcrilaBond to 2 gallons of water and start painting the house with it. When he is done he better be soaked with the stuff. Slather it on good.
7) in a wheelbarrow (not a mixer he says) mix your mud using 1/4 gallon of the AcriliBond and add water as needed. Throw in one bag of stucco mix and one box of color dye. Never mix anything less or more at a time. This ensures a good color match from batch to batch. If you want you can throw a 1/4 shovel of lime in too. But that isn't really needed unless your gonna try and make it water proof. "Now don't get smart and lazy and mix the mud in a (expletive) mixer. You'll never get the color dye to mix completely and you'll see the difference."
8) get out your hod a slap that mud to her.
10) AND HURRY UP ABOUT IT YOU (expletive, expletive, expletive) LAZY SONS OF SKUNKS!! YOUR BURNING UP MY DAY LIGHT!!
Ok so I added #10. That is what he says about 7:05 am every day. And yes I still work for the old grouch sometimes. Hes really an old softy with a big mouth..... And a lot of wisdom.
As a hod tender of at least some experience I can tell you that your mud should be about the same consistency as pancake batter. Just not as lumpy.
I hope this has answered your question. If it has then please be sure to click on the accept button.
Best regards; The Home Smithy.
Your question was posted "How to apply stucco over painted concrete block? What materials are needed? The paint is in good condition. I pressure washed it but want to make sure the stucco sticks & I don't have problems later."
Based on the information you provided I tried to give you the best advice without knowing all the facts. Your response clearly gave "The Home Smithy" a better idea of where the work would be done (outside) to prepare an answer.
When a customer submits a question we hope to get as much information concerning the subject matter to give a good clear response. Basically, the two answers you received run parallel to one another, preparation and product selection is key to a good job. The Home Smithy is suggesting to use someone to do the work and I believe you're trying to do this yourself. The technique in applying the material varies, some use different methods for applying these materials, trowels, straw-brooms and even specialized spray-ons.
In response to your comment, "How many years have you applied stucco on the outside of homes?" I have done none, I have experience in interior applications and gunnite experience for in-ground swimming pools. I also have installed ans prepared dry-wall for paint and other applications. Again, based on your question I provided the best advice i had at the time.
Good Luck with you project.