How to Prevent Efflorescence
An ounce of prevention can eliminate many of your efflorescence headaches, but you'll have to rely mainly on your contractor. Good building practices are essential. Remember, you're trying to avoid the three essentials of efflorescence: keeping salts out of the masonry, keeping water out of the slab and avoiding porosity in your stone work.
Here are some of the key things you should insist on from your masonry contractor:
- Use high quality concrete that contains minimal water. In the business, this is known as "low slump" concrete. Compact and finish the concrete well to minimize its porosity.
- Make sure the sand and gravel used in concrete has been washed and that the water in the mix is pure and salt-free. Adding fly-ash to concrete also reduces the water and cement that are needed and binds some salts, minimizing efflorescence [source: Bannister].
- Use low-alkali mortar for stone or brick work so that alkali salts don't leach into the masonry. Mortar should be firm and free of cracks. Make sure the manufacturer of fired clay bricks has added chemicals during manufacture to make salts in them insoluble and limit efflorescence.
- Cure concrete or stucco properly. Keeping a concrete slab wet and covered with plastic while curing makes it denser and leaves fewer channels through which salts can wick to the surface [source: Nasvik].
- Consider a sealer or paint that will minimize efflorescence. Since some sealers can trap the deposits and make them harder to remove, this decision should be left to an expert.
- Install a vapor barrier under the slab in order to keep moisture from seeping up from below. Seal footings with plastic so water doesn't seep from the ground into the foundation. Proper flashing, wall covers, roof overhangs and window caulking all protect masonry, too.
Once the masonry is in place, it's up to you to discourage efflorescence. Watch out for lawn sprinklers, excessive washing and splashing -- any wetness encourages the problem. Improve drainage by routing runoff away from your house, patio or wall.
The bad news is that efflorescence may not be entirely preventable. But the good news is that however annoying it may be, it's usually not a huge problem and may even go away on its own. Don't be impatient. When the restoration of Michelangelo's Sistine Chapel ceiling began in 1975, the first step was to waterproof the vault to prevent any further efflorescence. And when the 19-year project was completed, the art work didn't look half bad [source: Capel].