Cleaning & Painting Concrete Block Exteriors

Concrete Block is a very common type of masonry building material used in commercial and industrial exteriors. A composite made from several types of materials—concrete, cement and aggregate—concrete block is affordable and long-lasting. When concrete block is used in new construction or remodeling, it comes together more quickly than brick, since fewer units are ultimately used. Other benefits of concrete block include its energy efficiency and eco-friendly materials.

Lakeside Painting has a long history of painting concrete blocks exteriors for our various Southeastern Wisconsin and Northern Illinois commercial and industrial business customers.

Inspect for & Repairing Cracks

Before cleaning and painting concrete block exteriors, a facility manager and painter should inspect the walls for cracks. This is vital in order to control moisture and ensure a long-lasting paint finish. An inspection for cracks also ensures structural integrity and the stability of the wall. Any number of things could causes cracks, from moisture and thermal expansion to foundation settlment and bad support. Weather changes (a strong winter, for example) can cause cracks to shift, while other cracks remain static. 

Structural engineers should be called in if the crack looks as though it is threatening structural stability. Settlement cracks, for instance, appear diagonal or stair-stepped and and will first appear near the floor. Depending on the building's construction and the extent of the cracking, additional structural support may prove to be a necessity. Smaller cracks should be sealed to prevent against moisture intrusion.

Mortar joints—the spaces in between concrete blocks—can also deteriorate over time due to moisture migrating into the building's structure. Freeze/thaw cycles and poorly mixed mortar can both precipitate the deterioration process. They should be inspected to make sure they are intact and solid rather than deteriorated. If the mortar joints are largely stable, then we can repair them with some tuck-pointing or "repointing," which is the process of applying fresh mortar to mortar joints.

All holes, scrapes and gouges in the concrete block should be fixed prior to paint application. Masonry repair material, not caulks or sealants, should be used to repair the block in such cases. Likewise, all spalled block, cracked sealants, flashing failures, galvanized parapet cap corrosion, damaged weep (drainage) systems, and gutter leaks should be inspected and repaired before painting as well. 

Lakeside Painting is an Industrial and Commercial Painting Company serving Milwaukee and Southeast Wisconsin. Vigilant about safety and dedicated to quality, we understand the complex needs of active businesses. At Lakeside, we adapt to provide you excellent, individualized blast cleaning and painting services.

Cleaning Concrete Block

When painting an existing, previously-painted concrete block structure, Lakeside Painting uses high-pressure washers (up to 6,000 psi) to remove all dirt, dust, and oxidized and/or failing paint. Loose mortar or cracks will need to be tuck-pointed after pressure-washing. Any aged and deteriorated control joints must be removed and replaced with new backer-rod and urethane sealants. Some buildings have, from nature’s expansion and contraction processes, established their own control joints commonly known as stair or step cracks.

Since they move, these voids are better treated like control joints. At Lakeside Painting we grind them out with diamond blade grinders, then install backer rod and urethane sealants, which better accommodate continued movement.

Painting Concrete Block Exteriors

As with almost all building units (save for certain bricks), concrete block requires a paint job to waterproof and preserve the building's structural integrity and create an overall aesthetic look.

Paint application depends on whether the block surface is smooth or textured. Smooth will require less paint, while textured (split-face) will have a rougher, almost gravel-like surface into which the paint must be worked. Split-face will typically require twice as much primer and paint than smooth block. The multiple coats of primer will help fill the porous split-face block.

We typically use 100% acrylic coating as they outlast oil paints by a wide margin. A sprayer will likely be used to apply the coatings; however, all coatings are back-rolled and/or brushed into the masonry surface. This is a very important measure, as a pinhole-free surface is essential to inhibit moisture intrusion into the masonry surface, which is the leading cause of most coating failures.

Careful observance of the aforementioned guidelines allows Lakeside Painting to offer up to Ten Year “Labor and Material” warranties. 

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