Commercial Painting Problems & Solutions – When Paint Peels From Brick

Brick is a challenging surface to paint.  But its grooves and valleys are the least of any applicator’s concerns.  Because the real distressor lies within the mortar. Here are The Problems That Can Happen When Painting Commercial or Industrial Masonry

Masonry and block walls are held together with mortar mixes.  These mortar mixes offer excellent adhesion and compression strength, which allows the structure to maintain its integrity.  However, these mortar mixes are also made from many soluble salts.  And when these material get wet, moisture wicks the salt water to the exterior of the brick and mortar joint.  When the water evaporates, the brick substrate is left with a layer of sodium film, which prevents the paint from adequately adhering to the substrate, causing it to peel and disbond.

Additionally, efflorescence can become a major compromisor for painting brick and masonry.  But this is typically a problem with new construction.  After masonry is completed, it’s common practice to wash the brick or concrete with a muriatic acid to clean away excess mortar.  This does well to improve the initial appearance.  But if the rinsing isn’t thorough, the muriatic acid can alter the chemical compound of the salts.

The alteration causes the salt to absorb water at an increased rate, causing it to swell and expand in size.

In the picture above, you can see the results of the salts mingling with the muriatic acid.  This is what efflorescence looks like.  And if you put a coating on top of freshly washed concrete or masonry, then you could have a surface that appears like this:

And as you can see in the image above, the salt is reacting, and causing the efflorescence to press against the coating.  In the image above, the paint has enough elongation, or flexibility to tolerate the pressure without failure.  However, a lot of coatings do not have the same elongation, and are more susceptible to rupturing.

The Solution to Efflorescence Paint Problems

There’s not coating it.  You have to physically remove the efflorescence from the substrate.  Wire brushing is a nice recourse.  However, it can be labor intensive if the area has a large accumulation of it.  In that care, high-pressure power washing is usually the best method, because you can cover a lot of area in a short amount of time.

Some painters and contractors will recommend using a masonry patching compound, or a latex concrete patch or caulking compound.  They are designed to adhere to the substrate, and mitigate the efflorescence and soluble salts.

But again, this method can prove tedious and even egregious if you’re an unskilled at the art of masonry.  So, as commercial painters, our best course is to apply a block filler over the masonry.  Block filler is typically engineered with alkali-resistant compounds that resist and neutralize the efflorescence from starting.  Concurrently, block filler has excellent moisture resistance, which prevents moisture from coming in contact with the salts, preventing them from expanding.

Another low-concern you may want to consider is the exterior temperature of the surface.  Certain temperatures can attract moisture, which can exacerbate the efflorescence effects.  Here’s a wide range of infrared thermometers to help you know the surface temperature.

But, if you want to cover all sides of the problem, you should consider painting the opposite end of the wall or surface.  Even though you use a block filler, it only prevents moisture from entering on the side being painted.  Moisture can still enter the masonry from the opposite side of the masonry.  So to take the necessary precautions, you should be applying another high-quality masonry coating.