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Re: purposely permeable concrete

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Often, the older buildings have been modified so many times - floors cut
up -  that any original barrier is gone.

Russ Nester
rnester(--nospam--at)juno.com

On Tue, 9 Jun 1998 05:34:37 -0700  "Canitz, Charles F NAB02"
<Charles.F.Canitz(--nospam--at)nab02.usace.army.mil> writes:
>Russ -
>  I've also encountered this problem. A few years past, I was the PM 
>for the
>upgrade of an existing 30 year old building. Part of the upgrade 
>included
>replacement of a VAT flooring located in the lobby with rubber 
>flooring.
>After in-place for a few months, several of rubber tiles lost their 
>bond to
>the 5" concrete slab on grade. When a tile was removed, moisture was
>evident. Prior to placement of the new flooring, water vapor 
>transmission
>tests occurred per the flooring manufacturer's requirements. However, 
>said
>tests occurred after all of the existing VAT was removed(lessons 
>learned).
>The new rubber flooring apparently acted as a watertight membrane 
>while the
>VAT was a lot more permeable and didn't trap the water vapor. It was 
>also
>subsequently discovered that no vapor barrier occurred below the slab.
>
>Charlie Canitz 
>
>> ----------
>> From: 	rnester(--nospam--at)juno.com[SMTP:rnester(--nospam--at)juno.com]
>> Reply To: 	seaoc(--nospam--at)seaoc.org
>> Sent: 	Tuesday, June 09, 1998 12:23 AM
>> To: 	seaoc(--nospam--at)seaoc.org
>> Subject: 	purposely permeable concrete
>> 
>> Permeable concrete sounds like a guarenteed failure for the 
>flooring. 
>> The planned sheet vinyl flooring will then become the vapor barrier, 
>even
>> if the concrete is of normal porosity.  In dozens of buildings built 
>in
>> the 1960's and 70's, I have seen two interesting rphenomena.  The 
>first
>> is that the water pressure will eventually lift the flooring off, 
>glue
>> and all.  The second is that the concrete underneath will be dark,
>> indicating water saturation.  In the most extreme case, with a more
>> modern urethane floor, blisters formed on the flooring, and if 
>punctured
>> would actually squirt water.   Similarly, plywood or OSB placed on a 
>slab
>> w/o a proper vapor barrier will swell and raise up, eventually 
>requiring
>> total replacement. If the flooring is to last, there must be an 
>effective
>>  vapor barrier under the slab.  
>> 
>> Russ Nester
>> rnester(--nospam--at)juno.com
>> 
>> 
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>> 
>
>
>

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