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Hushpuppy 11-24-2006 08:16 PM

Making an 8" hole in the brick
I have an old brick home, built in 1926 or thereabouts. It's actually a 2-unit building; we are on the second floor. The outer walls are made of 3 courses of brick; there is no framing as you'd see in newer construction.

I need to open an 8" diameter hole in the brick, so I can put an exhaust fan over the stove and have it exhaust to the outside. My friend rented some sort of brick hole cutter from Home Depot and said it was easy to make a nice big round hole all the way through your brick. My question is this:

Assuming the brick is sound, is this hole too big to be putting in the side of my house? I don't want to weaken the wall. Do I need to shore up the brick at all in the hole? (Ie, maybe there's some sort of liner or something I need to use in there; who knows?)

Because of space constraints, my hole will be 5" from the side of the chimney. I dunno if chimneys add any structural burden to the issue, or if there is some sort of minimal distance to the chimney because of the danger of exhaust gasses rentering the house (but the hole will be a good 6 feet down from the top of the chimney).



joasis 11-25-2006 08:03 AM

I think you need to back off and be sure you are completely certain you are making the right approach. Exhaust fans can be adapted to a rectangle opening, that would allow a nicer cap outside, plus allow you to chisel out the bricks carefully to size, hand..hammer and brick chisel. I cannot imagine what Home Depot rented you to cut an 8 inch circle in it is a small demo hammer, and you need experience with those or disasterous results will be obtained.

majakdragon 11-25-2006 08:11 AM

I agree with joasis. The only tool I know of that will cut a really nice round hole is a diamond bit drill. They don't rent these at HD. It is likely you will end up ruining a bunch of bricks. Hand scoring with a chisel is the best way to do this. 8" is a pretty big hole for a bathroom exhaust fan.

mdshunk 11-25-2006 08:43 AM

I've core drilled an 8" hole in a brick curtain wall, but not a structural brick wall. I'm not so sure I'd core that big of a hole in a structural brick wall. Leave that up to a mason. They can install a proper lintel that would be required.

Consequently, 8" round is the normal size for a through the wall range exhaust fan.

Hushpuppy 11-25-2006 09:15 AM

Thanks for the replies!
Thanks for the replies, guys. Looks like I need a mason...:hammer: Yes, this is for a stove in the kitchen, not a bathroom, and it's asking for an 8" hole to get the proper airflow that we want.

concretemasonry 11-25-2006 11:44 AM

Have a mason do the sawing - He can do it easier, faster and with less mess. - And probably cheaper if you consider all the time, rental and running.

Drilling a hole as small as 8" in a thick masonry wall should not require any reinforcing because the the naturak "arch action" of the masonry. The loads are naturally spread out. Your walls are as thick as they are because of the thickness of the lower walls and the desire for uniform construction from top to bottom. I have seen 20 story buildings built out of 6" thick block walls with no steel or concrete columns or beams. - It is not a serious as drilling a hole in a wood joist that carries a much more concentrated load.

mighty anvil 11-28-2006 07:17 AM

brick hole
If this is a brick veneer cavity wall the important issue is flashing of the backup wall. The larger the initial brick opening, the easier it will be to install flashing. When this flashing is omitted, water penetration will usually depend on the density of the brick and mortar.

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