Foreman Ed Erazo, SparkleWash Construction Services, Omaha, Neb., uses low pressure spray to apply Sure Klean Vana Trol masonry cleaner to a mixed masonry elevation at an under-construction shopping center in Papillion, Neb. photo courtesy Craig Christensen.
The editor of a construction trade magazine called the other day.
She wanted to understand masonry cleaning, since she planned to feature this important but not-so-well-understood facet of masonry construction in an upcoming issue. She wasn’t afraid to ask about the basics, either.
She sent me a list of questions. I answered them, and after checking my answers with our in-house experts, returned the list.
Here’s the masonry cleaning Q & A:
What is the cleaner supposed to do? Simply remove excess mortar, dirt and grime from the surface of the brick, stone or CMU? Or more?
Cleaners for new masonry construction remove dried mortar smears and splashes from the masonry. They “clarify” mortar joints, removing the bit that has bulged out during tooling, so the joint has nice neat edges. On colored concrete block masonry, good cleaners also improve “color uniformity” building-wide.
This photo shows the basic purpose of new construction cleaning — remove excess mortar and clarify mortar joints.
Restoration cleaners remove a host of contaminants from historic building fabrics, from biological staining to atmospheric soiling from decades of air pollution caused by cars and factories.
New construction cleaners and restoration cleaners should do their jobs without damaging the masonry.
This before-and-after photo shows restoration cleaning under way on a 1928 apartment building in Gary, Ind.
What isn’t it supposed to do? Sink into brick and mortar joints, because that could cause what?
Above all, cleaners should not damage the masonry. Other things they shouldn’t do include staying on the surface too long. They can dry out and become one more unsightly contaminant, especially if they contain dissolved mortar or other soiling. If applied at too high a pressure, they can penetrate the masonry too deeply to be rinsed away. If the cleaner starts to dry before the dwell is complete, reapply.
What do you mean by masonry “substrates” when talking about the mock up panel?
Whether referring to a test or mock-up panel, or the building itself, “substrate” is jargon for the particular kind of masonry material. For instance, clay brick is one kind of substrate, and concrete brick is another.
When is the bucket and brush method needed? Is that ever the best choice?
Bucket and brush is appropriate for indoor cleaning where water must be tightly controlled. Also for cleaning isolated areas and features outside. Bucket and brush doesn’t distribute the cleaner as uniformly over a large area as low-pressure spraying, however.
This is a good place to mention the 4-step method for masonry cleaning.
Why was raw acid ever used? Why isn’t it anymore? Was it always muriatic?
Pre-World War II, masonry pretty much meant red clay brick and gray mortar. Red clay brick is highly acid-resistant, so to clean the acid-soluble excess mortar, masons used cheap, abundant muriatic acid, a by-product of steel manufacturing.
Since then, manufacturers have developed an enormous range of masonry products, in all colors, both clay and acid-soluble concrete. Ingredients to create colors and effects in clay brick, such as vanadium salts (beige brick) or iron (iron spot brick), for example, can react with acid to mobilize ugly stains. So manufacturers created cleaners that use only tiny amounts of acid, controlled and enhanced with detergents and buffering agents.
These proprietary cleaners, made specifically for cleaning, come with precise application and safety instructions, and warranties. Follow directions, and you can count on the result. This is not the case with muriatic acid, which is just a byproduct, and never intended for masonry cleaning. It has no warranty, safety or application instructions, let alone any kind of tech support.
The good news – the contractor saved a couple bucks by using muriatic acid to clean the masonry. The bad news – Cleaning with muriatic acid caused these ugly stains which equal thousands of dollars in damage.
As a byproduct, it contains impurities, which accounts for the yellow color. These impurities can stain mortar joints during cleaning.
Muriatic acid is cheap and abundant which is why some contractors use it, even though the Brick Industry Association, Mason Contractors Association and other industry groups have come out hard against muriatic acid. Many brick manufacturers include pallet tags with their products expressly warning against cleaning with muriatic acid. But old habits die hard.
Is there a maximum PSI for water pressure?
For rinsing masonry, 1,000 psi is probably as high as you want to go. Again it’s quantity of water used (gpm) rather than psi that governs the effectiveness of the rinse. The higher the psi, the more chance you have of scarring the masonry with “wand marks.” In the dimensional stone industry, as you may know, super-high psi is used to cut stone.
Another element to consider in pressure rinsing is the radius of the spray, commonly referred to as the “degree of fan.” A thousand psi at zero degrees of fan would basically be a laser beam, scarring the masonry. The same psi at 40 degrees of fan (recommended) will give you a good rinse.
PSI also refers to the water just as it leaves the nozzle. The stream loses some of its velocity between nozzle and wall. Keeping the nozzle about 18 inches from the masonry is recommended.
High pressure and a narrow fan have scarred this concrete masonry — without doing a very good job of cleaning,
If a cleaning plan is discussed in pre-construction, should it also be specified?
The cleaning plan should always be discussed pre-construction, and proper products and procedures specified. It isn’t always, and projects often pay the price.
Whose job is it to design the cleaning plan and to approve of the job when done?
G.C., architect, mason and cleaning sub should work together to design the cleaning plan, with input from the masonry manufacturer. Whoever has overall responsibility to deliver the building to the client – usually the architect — should approve the completed project.
Is the cleaning typically done by the mason contractor or is that work sub-contracted out?
It can and is done either way. If sub-contracted, the mason contractor still needs to ensure proper products and procedures are used.
Bad cleaning looks bad but may also damage masonry. How?
On clay masonry, some forms of improper cleaning, like using muriatic acid or not properly pre-wetting or rinsing can etch mortar joints. Exposing the softer layers beneath the surface decreases the mortar joint service life by making it more vulnerable to freeze-thaw cycling and other forms of deterioration. Eventually, water gets in the building envelope.
The same can happen with concrete masonry, only the CMU is also vulnerable along with the joint.
Above all, cleaners should not damage the masonry. Here, a cleaner not made for concrete masonry etched the joints and the block surface. In addition, the masonry was likely not properly pre-wet or rinsed.
Does masonry with a water repellent coating need different treatment than “raw” masonry?
New-construction cleaning – removing excess mortar and clarifying mortar joints – should be conducted before applying a water repellent. A finished building with a water-repellent applied will still need maintenance cleaning. But this will be a different type of cleaner than used for new-construction cleaning, because the soiling to be removed is different.
In general, maintenance cleaners are less complex and less aggressive than new construction cleaners.
Is it appropriate to ask about cleaning historic or existing buildings?
Yes, because anything outside gets dirty and needs to be cleaned — especially after half a century or so.
Anything outside gets dirty — just how dirty a building can get is shown here during restoration cleaning of Chicago’s Randolph Tower, with PROSOCO’s Sure Klean Restoration Cleaner, natch.
Is that process different?
The basic procedure – soak or “prewet” the surface; apply the cleaner; dwell and agitate; rinse – is usually the same for restoration and maintenance cleaning as it is for new construction cleaning.
Is the product used different?
The products are different from new-construction cleaning, because the contaminants and masonries are different. You always want a cleaner specifically designed for the masonry you’re cleaning and the contaminants you’re removing. Just as there are different products for different kinds of new construction cleaning – clay and concrete, for instance, so there are different kinds of cleaners in restoration cleaning for, say, granite and limestone.
Removing biological soiling from old acid-soluble limestone takes a much different kind of cleaner than removing dried mortar from new acid-resistant clay brick.
Can you list, generically, the best kinds of products for different masonry materials (one for brick, another for block, another for limestone, etc) without using brand names?
Your best bet for cleaning any kind of new masonry is to locate a cleaner designed for that specific kind of masonry. Cleaning red clay brick? There’s a cleaner made for it.
Cleaning cast stone (a concrete product)? Use a product specifically designed for cast stone.
Removing atmospheric soiling from 100-year-old limestone? Make sure the cleaner is designed specifically for that chore.
If you’re in doubt, call the manufacturer’s toll-free customer care number. If there is no number, don’t use that product. Use only cleaning products backed by free, readily available manufacturer tech support.
The cost of damaging a building is too great to be anything but one hundred percent certain that you’ve got the right cleaners and procedures.
If you see one product that claims to clean every kind of masonry – and there are some out there – run. One product cannot clean every kind of masonry and every kind of soiling any more than one kind of saw can cut every kind of material, or one kind of hammer can do every construction job.
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