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Old 09-13-2009, 09:36 AM   #1
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Questions about installing bathroom vent fan


I have a couple of mounting questions pertaining to a bathroom vent fan. I have a mounting kit with instructions but my question concerns specifically with cutting a hole to the outside. I need to cut a 4" diameter hole to the outside and the area where I need to cut the hold is an exterior load bearing joist (below that is brick and block). I know this shouldn't be an issue but I have another hole a few feet down that brings in my electrical. I wasn't sure how far away a hole needed to be from another hole on an exterior joist before it could create problems with structural rigidity.

Also, I believe any hole cut should be dead center in the joist, correct?

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Old 09-13-2009, 11:05 AM   #2
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Questions about installing bathroom vent fan


Are you planning on cutting through the rim joist or a floor joist? You can cut through a rim joist for the duct, but not a floor joist.
Ron

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Old 09-13-2009, 11:25 AM   #3
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Are you planning on cutting through the rim joist or a floor joist? You can cut through a rim joist for the duct, but not a floor joist.
Ron

The rim joist. The exterior joist that goes around the house, not the floor joist.
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Old 12-31-2009, 11:32 AM   #4
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Questions about installing bathroom vent fan


I need to cut a 4 1/2" circle in the rim joist. Should I cut this hole center in the joist or closer to the bottom of the rim joist?

I was reading this:

http://askville.amazon.com/largest-h...uestId=7847396

Last edited by tripower; 12-31-2009 at 11:39 AM.
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Old 12-31-2009, 12:20 PM   #5
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Questions about installing bathroom vent fan


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Originally Posted by tripower View Post
I need to cut a 4 1/2" circle in the rim joist. Should I cut this hole center in the joist or closer to the bottom of the rim joist?

I was reading this:

http://askville.amazon.com/largest-h...uestId=7847396
I would cut it in the middle.
Ron
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Old 12-31-2009, 12:55 PM   #6
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Questions about installing bathroom vent fan


Quote:
Originally Posted by tripower View Post
I need to cut a 4 1/2" circle in the rim joist. Should I cut this hole center in the joist or closer to the bottom of the rim joist?

I was reading this:

http://askville.amazon.com/largest-h...uestId=7847396
A neighboring county building code is real rigid as far as adhering to code issues. I recently had the same scenario you are dealing with and double checked with the inspector before I drilled a hole in the customers house. Basically, there were no specific code requirements as far as location on the rim joist. Of course, your local codes may differ.

You may want to check the exterior location of the proposed hole and determine where the flange to the vent cover lines up the best with your siding. Depending on your siding style you may want to line it up a specific way to accommodate the siding.

Kevin
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Old 12-31-2009, 03:40 PM   #7
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Questions about installing bathroom vent fan


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A neighboring county building code is real rigid as far as adhering to code issues. I recently had the same scenario you are dealing with and double checked with the inspector before I drilled a hole in the customers house. Basically, there were no specific code requirements as far as location on the rim joist. Of course, your local codes may differ.

You may want to check the exterior location of the proposed hole and determine where the flange to the vent cover lines up the best with your siding. Depending on your siding style you may want to line it up a specific way to accommodate the siding.

Kevin
I have two other pre-existing holes in my rim joist in other areas of the house. Both are around 3" in diameter. I really am not comfortable cutting the hole larger than that. Not to mention that upon closer inspection the area that I am cutting has the rim joist already with a notch about 5 x 11" to make way for an air vent (orig construction). I want to maintain the structural rigidity of the rim joint.
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Old 12-31-2009, 05:01 PM   #8
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Questions about installing bathroom vent fan


The rim joist sits, full bearing, on a plate member in Western construction. Under this is concrete, block, wood, etc. wall. You can cut a section out as long as there is no point (concentrated) load above. A post or jack stud of a window, directly above. When installing rim joists (which transmit distributed loads to the foundation) it is acceptable to use shorter pieces. 16", 4', 2', mix and match, so long as they are properly nailed to the plate member. They have full bearing, you can drill or cut any size hole as long as the rim holds the other joist's ends in line, from rotation, their other job. If a stud above has a load from the roof, usually the load would be transmitted down by the plate and rim below. But sometimes the plywood sheathing shear comes into play, carrying some of that load, distributing it to areas next to the stud/rim. There are rules to follow when drilling joists that are clear spanned, not when fully bearing. At least for a 4 or 6" hole with no point load above.

The fan duct termination should be 3' from any outside openings (doors, windows) or the plate line of the building. Keep it away from the furnace or other intake--- 1.EXHAUST FANS: IRC Section M1501, WSVIAQ 302.2.1. IMC 501.2, 501.2.1 Exhaust fans are required in each kitchen, bathroom, water closet room, laundry facility, indoor swimming pool, spa and other rooms where excess water vapor or cooking odor is produced. The air removed by every mechanical exhaust system shall be discharged outdoors at a point where it will not cause a nuisance and from which it cannot again be readily drawn in by a ventilating system. Air shall not be exhausted into an attic or crawl space.


Your local energy may require additional rules.




Be safe, Gary
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Old 12-31-2009, 08:15 PM   #9
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Questions about installing bathroom vent fan


Tripower,
Are you putting in a standard 4" duct? If so, you can get a 4 1/8" holesaw. It leaves you just enough clearance to fit the 4" duct through. Nice and neat, easy to seal up when you are done. Bosch, Milwaukee, Lenox all make that size.
Mike Hawkins

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