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Painting Brick Masonry

When Painting Brick Masonry make sure you dont trap water inside your walls, or your paint will peel off as the effloresence starts to bleed through the surface bringing the salts with it.

Although painting can make masonry look a little better at times, you really need to consider that it is all too easy to make it worse by trapping water inside the wall, this not only causes an interior swamp, your paint job will fail. It is wise to not cut corners with workmanship assuming you can cover it up with paint.

Make sure you fill the joints up tight with mortar to keep moisture out of the wall. Any moisture trapped behind the paint will cause problems later, such as paint peeling off the wall.

Water or moisture can enter masonry wall through incompletely bonded or partially filled mortar joints, coping, sill, projections or pop outs, or incomplete caulking and improperly installed or omitted flashing.

Before Painting Brick Masonry

Make sure there are no efflorescent materials in the mortar or brick. Efflorescence beneath the paint film can cause problems.

Each coat of paint is the foundation for the next coat, so your success or failure with painting will depend a lot on how well you prepare each surface. The first thing to do is thoroughly examine the entire surface to be painted. Previously painted surfaces often require the greatest effort. Remove all loose matter. Take special care to clean any surface that you will be covering with emulsion paint or primer, they require a cleaner surface than solvent based paints. Be sure to follow the manufacturer's directions about applying any paint to damp surfaces.

Preparing New Masonry

Usually you wouldn't paint new clay masonry. But if need be don't wash clay masonry walls with any acid cleaning solution. Acid reactions can make paint fail. Use alkali-resistant paints. Unless low-alkali portland cement was used in the mortar, neutralize the wall to reduce the possibility of alkali-caused failure with a zinc chloride or zinc sulfate solution of 2 to 3-1/2 pounds per gallon of water.

Preparing Existing Masonry

Examine older unpainted masonry for efflorescence, mildew, mold, and moss. Check for any possible entry points for water. If necessary repair any flashing and caulking and tuck point any defective mortar joints. Remove all efflorescent by scrubbing with clear water and a stiff brush.

If moss has accumulated on a damp shaded wall, wet the wall first with clear water and then apply weed killer. Chemical weed killers may add to efflorescence or reach unfavorably with paint. After you get rid of the moss, be sure to scrub the wall with a stiff brush and rinse with clear water to remove the weed killer.

Remove any mildew completely before applying any paint. It will continue to grow and damage new paint if you do not do this. You can steam clean or sandblast to get rid of mildew also.

This mixture works well too:

* 3 Ounces trisodium phosphate (Soilax, Spic and Span, Etc.)

* 1 Ounce laundry detergent (Tide, All, Etc.)

* 1 Quart 5 percent sodium hyperchloride (Clorox, Purex, Etc.)

* 3 Quarts warm Water, enough to make 1 gallon solution.

Using this solution, scrub with a medium soft brush until the surface is clean then rinse thoroughly. For small areas, use an ordinary household cleanser, Scrub with a medium soft brush and rinse. Use a mildew proof paint to keep molds from coming back.

Remove all peeled, cracked, flaked or blistered paint by sandblasting, scraping, or wire brushing. Blistering paint is usually due to moisture within the masonry unit. Find and stop the water from entering the masonry. If too many coats of paint have already been installed, remove them all to get the best look. Sandblasting is the faster way to remove large areas of paint.

Completely remove cement based paints before Painting Brick Masonry with other types. An exception to this rule is when you have used cement based paint as a primer and you will be doing the next coat with another paint within a couple of days. If you are going to repaint the wall with another cement based paint, just wire brush and scrub if you don't have any mildew, efflorescence, or any other problems of that nature when Painting Brick Masonry.

Selecting Masonry Paints

In selecting paint for Painting Brick Masonry walls, you greatest concern should be the characteristics of the surface and the exposure conditions of the wall. Choosing a good primer is important, especially where unusual or severe conditions exist. It's best to use an alkaline resistant primer.

Masonry paint should be durable, easy to apply, and should stick well. All paints have distinct properties, and the surfaces you put them on can very a lot when dealing with the many aspects of the masonry wall. Even the most experienced paint contractors have to examine a surface carefully before deciding which paint to use. Typically for exterior masonry, you will want to use a porous paint so any moisture in a wall wont be trapped behind the paint and cause it to blister etc.

Painting Brick MasonryBrick and Masonry Water Repellents

Summary: Brick, block, stucco, and mortar all contain little passageways that accept water. This can be positive depending upon exposure to the rain, snow, heat, wind, and temperature conditions, strength of the individual brick or block units, etc., it can work against the long term durability of the masonry. The two main categories of colorless coating to apply to Painting Brick Masonry surfaces are film forming sealants and penetrants.

Related Articles: Brick Veneer Leakage, Brick Water Repellents, Brick Leaks

Painting Brick Masonry with Water Repellents

Brick, cmu, stucco and mortar can absorb large quantities of water. In fact, brick / block masons often cover brick and cmu pallets on the job site to protect them from rain. The reason is simple. Brick and block have a property referred to as 'suction'. This suction draws water from wet mortar into a brick or a block when it is laid. This, in turn, rapidly sets up the wet mortar. This stiffening allows the bricklayer to continue to lay row after row of block and brick. If bricks absorb too much water, they can't absorb water from the mortar. When this happens, the brick or block can move around in the wall after it is laid. Those who live in freezing weather areas can testify to the power of freeze thaw. Let water soak into a brick, let that water freeze, and BINGO, major problems soon develop.

Many people have experienced efflorescence (white salt deposits) on brick or block. Efflorescence is made possible by the tiny passageways in brick, block and mortar. Water travels right through a brick and dissolves the salts. These salts deposit on the surface of a brick after the water evaporates.

Approximately 100 Years Ago

Many people have houses built from 'used' brick. These brick were often fired in low temperature kilns. The outer face each brick would become hardened, but often the core would remain somewhat soft. Some bricks would harden more than others depending upon their location within the kiln. It was an inexact science.

So the new bricks were not all the same. Some new brick can be soft. The clay used to make the brick can be of poor quality. The manufacturer may cut costs by reducing the amount of time the brick spend in the kiln. Quality control may have been non-existent.

The point is, in order to protect your brick structure, from the elements you may have to consider Painting Brick Masonry or sealing it with a clear sealer. Note; there is a big difference between products you may be considering.

Painting Brick Masonry - Sealers vs. Repellents

During the past 25 years, there has been a plethora of products that can be used to 'seal' masonry surfaces. The problem is, some things should be sealed and others should not.

My Webster's Dictionary defines seal as "a tight and perfect closure (as against the passage of gas or water)". Can you detect the problem? A true sealer will completely block the passageway of water. In fact, it will most likely block it no matter which direction it is headed (into or out of the unit being sealed).

There are two primary categories of colorless coatings that you might use for Painting Brick Masonry surfaces: film forming sealants and penetrants.

A film forming sealant produces a thin, solid film on the surface. A penetrant, on the other hand, is absorbed into the brick or masonry.

Painting Brick Masonry - Sealants

Sealants work great if you are trying to prevent absorption of oil, paint (graffiti), chemicals, etc. They also do a fantastic job of keeping water from entering brick or masonry, but they have serious drawbacks.

Sealants can slow down, or stop, the ability of a brick or masonry surface to breathe. Because they form a film at the surface of the brick or block, they stop trapped water or water vapor from escaping into the atmosphere. In colder climates, this can cause brick spalling (flaking) when water, trapped behind the sealant, freezes, expands and fractures the brick or masonry.

Film forming sealants can also trap dirt, discolor, change the color of the masonry or brick, and produce a sheen or gloss when applied.

Painting Brick Masonry - Sealant Ingredients:

Film forming sealants often contain one or more of the following principal ingredients:

  • acrylics
  • stearates
  • mineral gum waxes (paraffin)
  • urethanes
  • bsilicone resin

All of these ingredients act like paint when they come into contact with brick or masonry. They simply 'stick' to the surface and form a film. Some sealants are so heavy bodied that they can bridge small hairline cracks.

On a microscopic level, sealants are 'big'. Their large molecular structure does not allow them to penetrate into the small passageways in brick, block, stucco and mortar.

Often the principal ingredients of a sealant are listed on the product label. If you see any of the above things mentioned, you very likely are dealing with a sealant. Don't be tricked by labeling that says "Sealant" - "Water Repellent." Yes, sealers repel water, but you may want a product that allows the brick or block to breathe.

Painting Brick Masonry - Penetrants

Penetrating clear coatings are, in almost all instances, the top performers. These products are excellent water repellents. They can penetrate deeply, sometimes up to 3/8 inch into a brick or masonry surface.

Penetrants do not form a film on the surface of brick or masonry. Rarely do they change the appearance or color of the surface. They are able to penetrate because of their tiny molecular structure. These products coat the insides of the tiny passageways of the brick and mortar greatly reducing the freeze thaw problem.

The primary ingredients of penetrants are silanes, siloxanes, or a blend of these ingredients. Note that these two ingredients look very similar to silicone. Do not confuse them!

Silanes have a very small molecular structure. They can penetrate deeply into masonry surfaces. Siloxanes have a slightly larger molecular size, but they also penetrate quite well. Both of these compounds can chemically bond to the silica and alumina minerals often contained in brick, block, stucco and mortar. This bonding property and their ability to penetrate make for long service lives. Often these penetrating compounds can last in excess of ten years!

Be sure to read product labels. If the label doesn't say what it contains, call the manufacturer and ask. Always ask for the technical department when calling so you can get the details of what you are purchasing.

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