12" diameter hole through concrete brick exterior wall


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Old 09-20-14, 02:36 PM
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12" diameter hole through concrete brick exterior wall

Hello everyone,

I have a load bearing wall composed of 16 by 8 by 8 concrete blocks. I will be cutting a hole though the wall that is approximately 12.5" in diameter for a 12" wide venting duct. I plan on placing the hole not directly under one of the trusses, and there will be at least one complete concrete block row above the cut hole. My perception tells me that this shouldn't be a problem. Is this installation acceptable?

Thanks for the help,
Mike
 

Last edited by 951Michael; 09-20-14 at 05:20 PM.
  #2  
Old 09-21-14, 12:01 PM
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It's difficult to say, without knowing more details of the wall. Are the blocks filled, how many courses are above the hole location ("at least one" could mean 8 or 9), sill plate loading, etc.? Since such a large hole is effectively destroying at least one block, and possibly two, I'd be tempted to install a steel liner sleeve between the duct and the hole, to make sure there aren't any future wall problems.
 
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Old 09-21-14, 01:46 PM
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Are you going to hammer and chisel the hole opening or rent a monster hole saw?

Curious again, why the big vent hole, is this a commercial building? You mentioned truss loading so I assume an exterior wall. If so, then there will be a hood of some sorts?

Bud
 
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Old 09-22-14, 01:57 AM
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is this a diy job, pro w/diamond coring equip, or are you asking for feasibility of placing the hole where you want it ? if diy, how did you intend to make the opening - dia coring or hammer drilling ? if dia coring, how do you attach drill stand & base ? impo, 12" dia core holes are NOT diy but its YOUR hole & wall
 
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Old 09-22-14, 05:56 PM
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Basically, I plan on first making a hole with a hammer drill using a nice size bit and cutting the rest with a reciprocating saw blade specifically for bricks. And it is not filled with concrete

There is a sill plate on top of it.

At 12" diameter I will not be compromising a complete brick as the sides of the brick I cut into will still be intact - bricks are 16" wide.

There is one row on top of this brick that I am not cutting into. The bricks on top are obviously overlapping this brick as bricks do, so the sides of this brick that I cut into will still be giving there complete support to the two bricks above it.

I need the hole to move a lot of air for an inline fan that is 12".

Additionally, there is no truss located directly on top of this location. The trusses are about 24" o.c. And for the 12" hole, I am locating the hole almost in the middle of the two trusses.

Thanks
 
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Old 09-22-14, 07:45 PM
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based on the new information, go for it ! good luck !
 
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Old 09-23-14, 03:03 AM
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I don't know how well you can control the sawsall and make a neat hole. What I've always done when I didn't have a drill bit big enough for masonry was to drill a series of small holes along the perimeter of the desired opening and then finished it off with a hammer.

btw - the block is reinforced every 8" so it's not like the whole thing is hollow
 
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Old 09-23-14, 03:41 AM
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A fan that requires that size duct and hole becomes a concern for excess depressurization (or pressurization) when there are naturally drafted appliances in a home, like a furnace or water heater. If this is for a large range hood, when flow rates are at or above 400cfm then a make-up air supply is required.

Even if this is not a range hood, a high exhaust rate will need make-up air from somewhere, otherwise some combustion appliances will backdraft into the house.

Without more details I'm guessing.

Bud
 
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Old 09-28-14, 09:52 PM
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That is a good point. Although I think that there is enough holes in this building for it to be fine, but I think it would be nice to directly blow air in on the cool side of the house. I am installing this large fan to remove a lot of heat that is being blown out of some large equipment.

Do they make an intake fan of a sort that is specific for make up air? Sense I might have to make another hole on the cool side of the building, which is the only place to put it as there really is no roof overhang, I wonder how this goes?

Thanks
 
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Old 09-29-14, 06:19 AM
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A naturally drafted gas hot water heater or furnace are the most sensitive to a negative pressure. Without going back and reading, do you have either?

For reference, a range hood over 400cfm must include a make up air system. Searching for what they use for a solution might help.

Bud
 
 

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