What "seals" a concrete block and stucco house from rain?

Hi,
As a followup to a previous question I asked about our concrete block house leaking after Frances, I have a slightly different question now so I can hopefully learn more about block house construction:
Let's say a house has no "holes" or "gaps" in the roof or walls for water to easily intrude. When a builder builds a concrete block house, what actually stops water from "seeping" through the walls themselves into the hollow concrete block? I know concrete is somewhat porous and will absorb some water, but what is normally used in block houses to prevent that? I've heard that stucco itself is totally aesthetic and serves no "waterproofiing" or "waterblocking" purpose.
So...
Is the block itself supposed to resist letting water get inside itself?
Does the block normally get a "sealer" applied to the outside by the builder during construction to keep out water later?
Is the paint on the exterior supposed to be the "water block" to protect rain from seeping into the block?
Thanks in advance!
-- Vinnie
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Stucco does have some degree of sealing but the thing that really seals it is a couple coats of a good paint.
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Garage door in concrete block outbuilding was blocked up & made into a window... there's no stucco on that 2 car garage. It's strictly painted with a sealer and then exterior latex. The concrete block below the new window I probably painted with five or more coats of $20/gal one coat latex and the new block still absorbs it... next paint job it certainly will get a sealer applied there first.

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bumtracks wrote:

factory, and I remember they always had a product called Thoroseal in 5-gallon buckets, lined up against the wall in the front office / showroom. I just looked, and what-do-you-know I found it at http://www.ruberoid.ie/ruberoid31.htm on the web! I have no idea if it's the best out there, but it's certainly been around a while <grin>. The description says...
"THOROSEAL is a blend of portland cements, well-graded sands and chemical modifiers supplied in powder form. Mixed with water or an ACRYL 60 / water blend to a batter consistency, it can be easily applied by brush or spray to concrete and masonry."
(Beware - the site says there's a separate forumla for low PH applications.)
Steve Henderson
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bumtracks wrote:

might be http://www.thoroproducts.com/product_detail.asp?product_id=T520
Steve
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