"The famous towers of Babylon (the one still in existence being now known to
the inhabitants of that district as Birs Nimrod) were protected for no less
than twelve stories with a coating of a kind of concrete consisting of
crushed brick cemented together with bitumen, so as to effectually retard the
encroachments of both damp creeping up from the earth and the waters of the
Euphrates when that river was in flood. There is no doubt but that the sole
reason why the one still in existence, as well as other very ancient
buildings which are yet extant, has stood for such a great length of time is
that the builders invariably used bitumen as an admixture, even if not
actually by itself in its construction. . . "

The Temple of KARNAK, Luxor, Egypt
(12 century B.C.)
Arthur Danby
http://www.karnakcorp.com/

So, if tar spread all over masonry worked in Babylon, then why don't it work
so well on the backsides of brick parapets?

Shaman