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RE: CMU walls after fire

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Generally the CMU will also become discolored if exposed to excessive heat.  Any other testing you could do I would imagine would have to be destructive rather than non-destructive.


Matthew Stuart

Structural Department


-----Original Message-----
From: jrgrill(--nospam--at) [mailto:jrgrill(--nospam--at)]
Tuesday, October 03, 2006 2:28 PM
To: seaint(--nospam--at)
Subject: CMU walls after fire


I was asked to look at some CMU walls at a structure that was exposed to a fire.  The structure has been gutted with the exception of the exterior CMU walls.  The owner wants to use the walls to rebuild the structure.  The owner said that another engineer looked at the walls and said they could not be used that they had been damaged due to the heat of the fire.  I have not seen their report.  From what I saw, I'm not so sure the walls are not usable.

The walls are lightly scorched and for the most part near the bottom half of the wall.  I used first a jackknife, then a screw driver, then a cold chisel and neither the block or the morter appeared to be soft.  There was one area, that apparently the first engineer or possibly damage with equipment during the gutting process, where the CMU was scraped deeper than I was with my tools.  At that location I could scrape material from the block fairly easily, but at the surface it was more difficult.  I came back to the office in our basement where there is some 25 year old CMU walls and the difficulty in scraping the block was about the same.  There are some light gage lintels that have deformed due to the heat, but they can be replaced.  The walls are lightly reinforced/grouted, jambs at openings, but new bars can be cut in and grouted and a new bond beam can be installed at the top of the wall.  If additional reinforcing is added to the wall, footings will have to be investigated to determine their size/capacity.  The footings are monolithic with the slab.

Are there any difinitive tests other than what I have done to get a better feel for the integrity of the remaining walls?  Is there anything else that I can do, or things that should be looked at?

Thanks for the help,

Joseph R. Grill, PE

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