White powdery substance on basement walls - a problem?

Is this normal or is it a sign that I need to do something. I bought the house last year and the house inspector didn't mention it as a problem but now I read online ads from waterproofing companies that it's a sign that moisture is seeping through my foundation. I'm going to have a contractor come in to look at it this weekend but I understand that there are a lot of scare tactics employed by these folks to get people to overspend on waterproofing so I'd appreciate some education on what's normal and what is a problem.
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http://www.cement.org/tech/faq_efflorescence.asp

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Before the contractor arrives, test for damp. This is done by taping 8x11-inch sheets of plastic to various spots on the wall, and seeing how many days it takes before drops of moisture appear between plastic and wall.
Dry efflorescence from masonry is hardly ever structurally important -- usually just a nuisance (an extra source of dust.) If you do not like to see it, think about having the basement drywalled. Your contractor can estimate costs.
--
Don Phillipson
Carlsbad Springs
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Joe wrote:

Also make sure it is not as simple as an exterminator doing a "baseboard" treatment and the clay in the mixture is just showing up as would dirty water stains. It would wipe off and not return...unless of course the same exterminator came back...
Lar
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"Joe" wrote

Yes, wise to check. Tape some plastic over the affected spots and see if it gets really wet. If so, you have some seepage.
This is normal so dont panic unless it's right on a wood support member. Chances are, the most you need is some basement grade water sealing paint product.
If the one fellow tells you that you have a major problem, get *multiple* estimates because uness you have alot of crumbling mortor (would be obvious to the eye that it's falling out), you probably just have a little damp.
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Make sure water drains well around the outside of your house. Wait for a dry spell, then wire brush basement walls and apply a sealing plaster, I used a wallpaper paste brush. This will reduce basement moisture and is something you should do before ever finishing a basement.

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