hole in hardie lap siding

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Old 04-10-16, 10:49 PM
J
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hole in hardie lap siding

Hey all,
I am on a new project this week, I have an upstairs laundry room that has the dryer exhaust vent running up the inside of the wall and out the roof, the total run is about 24 feet. I am going to run the dryer vent right out the wall like it should have been in the first place but I am trying to figure out the best way to cut a 4 inch hole in the exterior hardie lap siding. I have never done any cutting in hardie so I am unsure of just how to go about doing it. And I also am curious if I need to do any type of weatherproofing around the hole I need to cut for the vent. Any help would be greatly appreciated.
 
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Old 04-11-16, 04:20 AM
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Hardie siding will virtually ruin a 4" hole saw, but you have a choice of spending $20 for a hole saw and taking a chance of it being dulled, or 2 or 3 times that for a coring hole saw. I would use the hole saw, make a really nice cut through the siding and the OSB underlayment and call it a day. Be sure to miss the studs as you drill

Milwaukee 4 in. Bi-Metal Hole Saw-49-56-9645 - The Home Depot
The arbor will cost about $15 if you don't already have one.
 
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Old 04-11-16, 05:48 AM
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Totally agree. You want the center of your hole to end up centered vertically on a single piece of siding... (for example, in the center of a 7" piece) not overlapping on 2 pieces. So measure down from the edge of the glass in a window on the outside... then transfer that measurement (center of siding) to the inside. If you need to mark the hole by drilling inside to outside, use a 3/8" x 12" hammer drill bit, or similar to mark the general location of the hole. But when you go to use the hole saw, drill your hole in the siding from the outside in.

Be sure you caulk the dryer vent on. If you were doing this as the siding was being installed, you would probably want to mount the vent on top of a 6x6 mounting block.
 
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Old 04-11-16, 06:22 AM
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The hole for a dryer vent needs to be 4-1/4 not 4" for several reasons.
Not going to get a 4" pipe into a 4" hole without crushing it, and any outside vent cover I've seen has a lip on the back side where the pipe slide in that would cause the outside cover to stand out away from the wall if the holes to small.
There's three different types of siding blocks. All are installed different.
If you use a surface mount you would need to drill the hole in the middle of the lap, not in the middle of the panel.
Mounting Blocks | Georgia-Pacific
 
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Old 04-12-16, 11:29 PM
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Thanks

Thanks for the help guys, I appreciate it a lot. Got some good advice to get this project finished.
 
 

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