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Efflorescence is more commonly known as chalking, due to its chalk-like properties.  Like most spalling, efflorescence is an ugly, but otherwise harmless.

A combination of the following three common circumstances causes efflorescence:

1. Soluble compounds which are part of the concrete.

2. Moisture combined with hydrostatic pressure that picks up the compounds and brings them to the surface.

3. Evaporation which removes the moisture, leaving the compounds in the form of a white chalk-like dust.

Efflorescence is a normal occurrence in concrete and is nothing more than an aesthetic nuisance, but it presents two significant problems when applying a concrete coating which are the following:

1. Prevents bonding – Efflorescence creates a physical barrier between the coating and the concrete.  If the coating bonds to the efflorescence instead of the concrete, it will begin to chip and peel after it cures.
2. Prevents proper curing – One “ingredient” of efflorescence is alkaline salts.  If the coating comes into contact with alkaline salts, it will not cure the way manufactures intend it to cure.  Not only will this cause problems with the coating after application, but it will also invalidate any manufactures warranty.

The hands down, best way to get rid of efflorescence is to grind it off.  Many “experts” recommend using a miranic acid wash to rid the concrete of efflorescence.  This will work temporally.   But because miranic acid is a liquid, and liquid is moisture ( hat tip to my second grade science teacher), one is really reintroducing one of the key ingredients (moisture) that cause the efflorescence in the first place by applying miranic acid.

If a grinder is not available to remove efflorescence, try a stiff steel brush.  If that doesn’t work, miranic acid will have to do.  I do recommend waiting for a week prior to applying a coating to make sure efflorescence does not begin to reappear.

Always, always, always, thoroughly rinse a floor with water after an acid application.

Final note on chalking:  Chalking is always a sign of the presence of moisture in the concrete. Remember: Moisture + coating = bad.  If you do not have a moisture meter, make sure that there are not any of the indicators mentioned in my previous post on moisture in the area where efflorescence is occurring.

Personal Note: Efflorescence is more commonly a problem of vertical masonry brick walls than it is of horizontal concrete surfaces.  In Minnesota, I have found efflorescence in the corners of garages or warehouses on the floor next to the exterior masonry wall.  It usually indicates that rainwater has found a way to penetrate the wall. In Arizona, it usually only occurs on walls that are subject to a regularly scheduled shower due to a misplaced sprinkler head.   Exterior wall moisture problems should be fixed prior to applying a coating, if possible – especially when applying epoxy, which takes seven days to cure.  If moisture is introduced to the coating environment prior to a full epoxy cure, IT WILL cause the coating to delaminate from the concrete.

There are two structural conditions in concrete that can interfere with a successful coating application.  They are spalling and efflorescence.  I like to call them the acne and dandruff of concrete.  Ugly and annoying,  but usually not deadly.

This post will address spalling.

Spalling is when small chunks of concrete become dislocated from the surface of the floor leaving a small divot in the concrete.  Spalling can range from a dime sized pimple to a full blown case of concrete acne.

Extensive spalling on a floor less than a year or two old is a sign of major problems with the concrete.  Either the air temp was to hot on the day of the concrete pour, there was too much water in the concrete when it was poured, or the concrete manufacture sent out a bad batch of concrete. No coating on earth will fix these problems.  The floor should be torn up and replaced.

Extensive spalling on an older floor (5+ years) is a sign that the original sealer has worn away and road salt or other chemicals have penetrated the floor and caused the concrete to break up.  This is normal and a little concrete TLC can fix these problems prior to the application of a coating.

The following is a question I always hear from customers:

“Won’t the coating cover that up?”

The answer is NO.  Coatings are not concealers.  Unless the spalling is smaller than a quarter and less than a 1/16” deep, the coating will not hide the imperfection. If not properly filled, spalling becomes more visible after a coating application due to the high reflectivity of most coatings.

“How do you cover up spalling?”

The best way fill spalling is with a powder based masonry product or with an epoxy based product designed for floor fill.  Use the following steps:

1. Place a high intensity light on the floor near the garage door with the light directed towards the back of the garage.  This will make all spalling easily visible.
2. If the spalling is old and dirty, chip away the top layer with a hammer drill so the filler can bond to the concrete.  Make sure to vacuum up any dust.
3. Wipe down the damaged area with acetone to remove any grease residue.
4. Fill the hole using a putty knife and filler material.  If you are going to grind the floor after filling, which I highly recommend, slightly overfill the hole.  This allows the grinder to grind the filler smooth with the adjacent concrete for a better finish, and also allows for shrinkage in the filler while it cures.

Note: Epoxy and masonry products have solvents and water in them that evaporate from the products while they are curing.  This will leave a slight depression in a previously filled area and may require a second application.

“How do you cover up extensive spalling?”

The short answer is: You don’t.  Like a severe case up acne it’s time to call the pros.  Any attempt to skim coat a large area or an entire garage floor will be an exercise in futility for the average homeowner.  Remember, you can still apply the rouge yourself but let a contractor fill the damage first.  A skilled masonry contractor can skim coat a heavily damaged three car garage in half a day, creating a smooth surface ready for coating.

Personal Note:  In my experience, in Minneapolis, MN, where salt is used on the roads for deicing, spalling is a common cosmetic problem that starts small and continues to grow over the years.  A properly applied epoxy/urethane or polyurea coating will prevent the problem from ever recurring.

In the Phoenix Valley/ Scottsdale, AZ area, I’ve yet to see a floor with extensive spalling.   Most likely, a floor in Phoenix with an extensive spalling problem would be an indicator of a larger problem caused by concrete being poured over hot desert earth on a hot desert day.

Inspection: KNOW YOUR MOISTURE CONTENT!!!

If you learn just one thing from this blog, let it be this: “Know thy moisture content.”

The effect of moisture on concrete coatings is often misunderstood by homeowners, overlooked by contractors, and is most often the cause of coating delamination several years after installation. If you think you have little or no moisture in your floor, run through the following site conditions checklist:

• Hydrostatic pressure
• Rapid changes in air pressure
• Cold air over warm concrete
• Warm air over cold concrete
• Humidity
• Spills
• Snow melt
• Roof leaks
• Garage door seal leaks
• Automobile AC condensation (often overlooked)
• Soap and water
• Rain water or irrigation system water leaking under garage door or service door (very common)

Concrete ALWAYS has moisture in it no matter how dry the surrounding environment may be. It’s not a question of “is there?” or “isn’t there?”, but of “how much?”

I have yet to inspect a floor where fewer than five of the above conditions have occurred. By using the right instrument, it only takes about two minutes to check the moisture content of a three-stall garage floor. There’s no good reason why this important step should be skipped, especially when considering how much money will be spent on the coating.

A visual inspection is not the right way to check for potential moisture issues.  Coatings fail when a floor is coated that is not visibly wet, but has a moisture content that’s too high to properly accept a coating. Concrete with 7% moisture content most often won’t be visibly wet, but it will still prevent most coatings from bonding properly. There are many different devices that are used to measure moisture content and all qualified contractors should own one. Ask your contractor about moisture content—it’s a simple way to check to see if they’re qualified. Professional contractors who install coatings for a living will give an educated response and have a moisture measuring device with them when they inspect the concrete—those who aren’t pros won’t.

If you’re a homeowner planning to install your own coating and have no way to check the moisture content of your floor, don’t let what I’ve just said scare you. I find moisture readings higher than 6% in about 1 out of 15 floors I have inspected in Minnesota.  In Phoenix, AZ I’ve yet to find an interior floor with a high moisture content, but I know I will eventually.  When I do, I’ll save that homeowner lots money and many headaches by taking care of the problem before I apply a coating.  Most of the time there’s an easily identifiable reason for a high reading. Nevertheless, here are a few precautions to take to lower the risk of moisture damaging a coating if you do not have a moisture meter:

• Don’t park vehicles that are dripping AC condensation in the garage for a couple weeks before the installation
• Don’t coat the floor during a high rainfall/humidity time of year
• Set a fan on low in your garage to circulate air for a few days prior to installation
• Call a pro and ask about soil conditions in your area. A local excavating company will know if your home is in an area that is likely to have high underground moisture levels

In some areas of the United States, nearly every concrete slab has moisture content over 6%. Contractors who work in rainy areas of Pacific Northwest typically won’t install any coating without first installing a special primer that acts as a moisture barrier. If you live in a high moisture environment, call a concrete products wholesaler and ask if they sell these primers to the general public.

If you  live on a hill or in a desert like the Phoenix Valley, do not assume your floor has moisture content below 6%. Hydrostatic pressure can push water into a garage floor in a hilltop residence the same way it does in low-laying areas. A hilltop location doesn’t necessarily mean dry concrete. Arid areas are typically much less likely to have high moisture readings in the concrete, but even in very dry areas concrete can hold the remnants of a spill or humidity for years in the right conditions.

In summary, I recommend DIY homeowners take these simple precautions to reduce the chances of a coating failing in their garage. If you’re planning on hiring a pro, ask him or her to measure the moisture content and ask them a few questions using the knowledge you’ve learned here. It’ll help you find out if the contractor is qualified to perform the work and will let the contractor know that you’re expecting top-notch service.

Personal Note:  While inspecting a peeling patio coating in Scottsdale, AZ, I was nearly blasted by the irrigation system when it turned on.  The irrigation happened to spray right over the peeling area.  I suspect that the interior of the concrete was extremely wet at the time of the coating application, but the surface had probably quickly dried in the heat so the coating was applied anyway.  Case closed.

Floor inspection: Overview

The first step toward a successful coating installation is a floor inspection. A proper inspection will consist of:

1. A moisture reading at multiple locations throughout the floor.
2. An inspection of the structural integrity of the concrete.
3. A survey of potential contaminants in the floor.
4. A discussion with the homeowner or business owner of the past use of the floor and the intended use of the coating (this will include presenting physical samples of the intended coating).

A thorough inspection takes only 10 minutes and will address or eliminate any unforeseen problems.

Step #1 is the most often skipped and most misunderstood step—which causes the most problems months or years down the road!

The reasons for this are many and will be addressed in my next post.

So your one-year old floor coating is beginning to crack and flake. You are extremely frustrated because: 1) you paid an arm and a leg to hire a contractor to perform a world class job and now you’re finding paint flecks on your car tires, or 2) you spent a long sweaty weekend cleaning out your garage, prepping the floor, coating the floor with an expensive coating, and now a mere 365 days later your floor looks terrible and you feel like you efforts were in vain.

This post and subsequent posts will be an exploration into the many reasons why this could be happening.

The potential causes behind a concrete coating failure are countless. Unlike vertical surfaces, horizontal surfaces are subject to all kinds of stresses that can cause a coating to fail—stresses from above, within, and below the concrete.  Concrete surfaces in a garage or harsh commercial environment magnify these stresses even more. A properly installed coating will be installed using a process- of-elimination method that greatly decreases the chance of failure due to stress.

This process of elimination can be broken into five categories:

1. Job site inspection and inquiry
2. Material selection
3. Site preparation
4. Coating installation
5. Post installation use

All of these processes are closely related to one another and must be executed properly in order to have a long-lasting, successful concrete coating.  Failure to properly address just one category, can cause the whole process to fail, no matter how well the other categories are executed.

Following blog posts will feature an in-depth exploration of each of the five categories.

My name is Paul Kariniemi. I am the owner of a concrete coatings company, Rocksteady Concrete Coatings, located in Phoenix, AZ and Minneapolis, MN. I recommend and install coatings for homeowners, contractors, and businesses. You can learn more about my company at www.rocksteadyconcretecoatings.com.  I emphasize polyurea coatings and concrete polishing in my business because they have beneficial characteristics that are not found in typical epoxy and urethane coatings.

I got into this business by chance while working as an industrial property manager and running a small heavy industrial general contracting business on the side. While building an aircraft hangar for a charter company, I was given instructions to install “whatever coating I thought was the best”. I had seen many failed epoxy coatings, many pristine epoxy coatings, and many coatings in between while working as an industrial contractor. Past experience convinced me that I was going to install the absolute best possible coating for an aircraft hangar floor. After many late nights and countless hours of research, I was absolutely hooked on concrete coatings!!!  Strange, I know.

I do not have a PhD in chemistry or a poster of the periodic table on the wall of my office, nor can I explain what happens at the atomic level while a coating cures (I’d sure love it if a visitor to my blog would!). My knowledge is based in countless hours of independent product research, in-the-field experience, and the hundreds of conversations I’ve had with chemists, sales reps, fellow contractors, and customers. I’m just a coatings junkie who loves the science behind making coatings, the common sense behind selecting coatings, and the art of installing coatings.

Thanks for stopping by my blog. Please post a comment or ask a question. It’ll make my day.

If you live in the Phoenix, Scottsdale, Sun City, or Cave Creek, AZ (or anywhere else in the Valley) area and have questions about coatings or have problems with an existing coating, feel free to give me a call.  I’ll stop by your place and perform a free inspection.  If you live in Minneapolis/St. Paul area, call me as well.  If I’m in town, I’ll stop by myself or else I will send one of my associates to answer your questions.

Los Angeles, CA and San Diego, CA also fall in my market area.  While I’m not in the area often, if you call me ahead of time I can make plans to stop by you place while I’m in town.

If you live elsewhere in the country and you can’t find the answers your looking for in my blog, or if your sick and tired of reading through pages of extremely boring concrete coating commentary : ) and want a quick answer, give me a call as well.  I deal with people all over the country over the phone – many times questions can be answered in short conversation.