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Re: FIRE - Fire damage to unreinforced brick wall.

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Stan,

The ability to scratch mortar out of the joint in a wall subject
to fire is an indication of spalling of the mortar.  Fire heating
the sand particles causes them to expand, causing (micro?)
cracking in the mortar.  The white residue that you have seen in
joints not directly exposed to fire may well be lime, however,
the mortar may not necessarily be a true lime mortar (*all* of
the mortar in that case could be easily scraped out), but a
portland cement-sand-lime mortar with an abundant amount of lime.
 (Masons love lime, it makes the mortar "fat" and easy to
handle.)

Examine the surface of the wall that was exposed to the fire by
tapping the brick with a hammer.  A dull "thud" will indicate
delamination of the brick and incipient spalling, while a "ping"
will indicate that the brick has not delaminated.  If the fire
was bad, I would suspect that you will have considerable
delamination and the expense of coring could be eliminated.  If
that is the case, then the recommendation would be to remove and
replace the damaged wythe.  Do you have any visible delaminations
or spalling of the brick? 


A. Roger Turk, P.E.(Structural)
Tucson, Arizona