How to Clean Exterior Brick

Cleaning Dirty Bricks

You should only use a powerwasher as a last resort - if you have a crumbling brick problem, this will make it worse. Simply spraying outdoor brick with a hose now and then rinses away any dirt that gets spattered on the bricks from sprinklers or rain.

For removing normal dirt and grime, simply rinse with plain water and scrub with a stiff bristled brush. For stubborn stains, add ½ cup of ammonia to a bucket of water and rinse well.

How to Clean Green Moss from Brick

If the brick is continually moist, it will almost always start growing a variety of molds and mosses. It is fairly easy to remedy.

Tools you will need:

Plastic spatula
Garden hose with pressure nozzle
High pressure hose
Chlorine bleach
Spray bottle
Soft bristle nylon brush (no wire brushes)
Eye protection, rubber gloves

How to do it:

Once a year use a garden hose, with a pressure nozzle, to remove as much moss as possible.
Periodically scrape off the moss or mold with a non-metallic spatula.
Mix one cup of bleach into a gallon of water.
Apply the solution on a small sample area first, then wait a week to see if there are any unwanted color changes in the brick.
If there are no unwanted color changes, thoroughly soak the bricks with water.
Using a spray bottle or hose spray attachment, spray the bleach solution on the bricks while they are wet.
Let it sit for a week, then thoroughly soak the bricks again with water.
Remove the moss with the scrub brush.
Rinse.
If this does not get all the moss, use a power washer to blast the rest off.
Better results are obtained when the moss is actively growing, but you should be able to remove the stuff even in cold weather. Avoid tightly focusing the spray or using so high a pressure that you damage the brick; start low and work your way up, keeping the pressure well below 3,000 psi.
Always rinse thoroughly with clean water.

Be sure to wear rubber gloves as you scrub, and don’t forget eye protection—scrubbing and spraying can splatter the bleach mixture toward your face.

How to Clean Cement off Brick

The easiest way to clean mortar or cement off of brick is with a chisel. If the brick has not yet been used in construction, you can also knock the cement or mortar off with another, damaged, brick. If the cement is actually embedded within the brick, you may have to resurface the brick to get it off.

How to Clean Rust off Brick

The strategy for rust stain removal is to remove the rust while not causing more staining or opening the surface of the brick and making it more susceptible to weather related damage. The only acid that will effectively remove rust is Oxalic acid, not muriatic acid, which is often recommended. Either may damage the brick and leave a stain – so test it on a small area first.

A favorable alternative to harsh acids is a liquid called "Klenztone", made expressly for this purpose.

How to Remove Oil Stains from Brick

Oil stains can be removed with a simple paste:

Mix one pound of trisodium phosphate and one gallon of water.
Add enough powdered chalk to thicken the paste.
Spread a 1/2" thick layer of paste over the stain and let it dry.
Remove the dried paste with a wooden scraper.
Wash the surface with clear water.

Paint Removal from Brick

Every so often, there is a vogue for painting brick facades, something that was seen in this country as early as the late 1700's and has rarely looked good. Removing that paint can be a maddening process. Sandblasting causes lasting damage to the beauty and integrity of brick and should never be used. Chemicals may be applied to remove chalk, calcium carbonate, and rust; chemicals must be spot tested in various concentrations. Too high of a concentration can etch the surface of the brick, damage window glass, or cause discoloration. Such procedures are best left to professionals.

Keep in mind, however, that some older brick houses were meant to be painted. They are constructed of rougher bricks, or seconds, and were designed to be painted to seal them from the elements. Often they were whitewashed, or painted with fanciful colors to mimic stone work. Such houses should be periodically repainted after doing the appropriate prep work. Use a paint that is formulated for masonry, usually 100% acrylic latex.

Fresh paint stains can be removed with a commercial paint remover or a solution of two pounds trisodium phosphate, available at paint and hardware stores, to one gallon of water. Apply the mixture to the stain and allow to dry. Remove with a wooden scraper and wire brush. Rinse with water. For older paint stains, you may need to use steel wool or a wire brush. Be sure to protect unstained areas from any chemicals you use.