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hollow sounding basement slab

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[#1] Posted: 04/22/2010 - 6:18:12 PM
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I inspected an old house today. It had a concrete slab in the basement that I'm pretty sure was poured sometime after the original construction.

Even more recently, a drain tile was added. The finishing layer of concrete over top of the drain tile must not be very thick because there was a very hollow sound when knocking on the concrete.

I didn't even use a dead blow hammer. Just knocking with my bare knuckle, it was easy to hear the hollow sound compared to the solid concrete and other areas.

How much concrete material should be on top of the drain tile after it's installed? I understand there's a pipe under there but shouldn't it sound more solid when knocking on it with my knuckle?

I'd show pictures but they don't really show anything since the whole thing was all painted.

John Dirks Jr - Arundel Home Inspection LLC - MD license: 29827
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hollow sounding basement slab
[#2] Posted: 04/22/2010 - 6:24:53 PM
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You can't draw a single conclusion based on a bare-knuckled rap on a basement floor, John. Nothing.


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hollow sounding basement slab
[#3] Posted: 04/22/2010 - 6:39:41 PM
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Quote: Originally posted by Jim Morrison

You can't draw a single conclusion based on a bare-knuckled rap on a basement floor, John. Nothing.




So the hollow sound does not necessarily indicate a problem. Is that a fair statement?

John Dirks Jr - Arundel Home Inspection LLC - MD license: 29827
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hollow sounding basement slab
[#4] Posted: 04/22/2010 - 6:48:15 PM
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Not just fair, John, true. How exactly do you measure 'hollow'? How hollow is too hollow?


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hollow sounding basement slab
[#5] Posted: 04/22/2010 - 6:51:58 PM
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Quote: Originally posted by Jim Morrison

Not just fair, John, true. How exactly do you measure 'hollow'? How hollow is too hollow?




Good points Jim. Thanks for the quick response.

John Dirks Jr - Arundel Home Inspection LLC - MD license: 29827
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hollow sounding basement slab
[#6] Posted: 04/22/2010 - 7:34:57 PM
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Hollow sounding concrete floors in Chicago basements can often mean there's been massive sewer backup. The sanitary sewer backs up, leaks out of the dry fit bell & hubs of the clay tile, and heaves up the skimpy concrete floor.

Rare nowadays though; that's old Chicago, pre-Deep Tunnel.


Kurt in Chicago

"If I smell it, it goes in the report".............Phillip Smith...2012


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hollow sounding basement slab
[#7] Posted: 04/23/2010 - 03:20:01 AM
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Google edge curl.
Chad Fabry
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hollow sounding basement slab
[#8] Posted: 04/23/2010 - 04:00:56 AM
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Quote: Originally posted by Chad Fabry

Google edge curl.


All I get on the first page is Photo Shop links.

Marc

"If Guam gets too overpopulated, it might tip over."
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hollow sounding basement slab
[#9] Posted: 04/23/2010 - 04:05:00 AM
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Quote: Originally posted by Marc

Quote: Originally posted by Chad Fabry

Google edge curl.


All I get on the first page is Photo Shop links.

Marc


Put "cement" after your "edge curl" search.

Terry



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hollow sounding basement slab
[#10] Posted: 04/23/2010 - 04:06:26 AM
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Got it, Thanks

Marc

"If Guam gets too overpopulated, it might tip over."
Congressman Hank Johnson (D) GA
   
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