Cutting Hole in Cement Block Chimney.

EarthWindandFire · Post by **EarthWindandFire** » Sat. Oct. 05, 2013 5:24 pm

Hi guys, I'm in the process of cutting a hole in my cement block chimney. The chimney runs up the center of the house which makes it draft well. If you look at the picture, it shows two block courses that I exposed after cutting away the Sheetrock. The photo shows three possible flue center lines.

Which location is the best to maintain chimney block strength and integrity. Also, does this look like a job for a hammer drill or a diamond-tipped hole saw?

Thanks!

McGiever · Post by **McGiever** » Sat. Oct. 05, 2013 6:24 pm

Guessing you have no tile flue liner behind those block???
So, no it does not matter. Pick one and give'er h3ll.

Hammer drill will do fine.

Post by **franco b** » Sat. Oct. 05, 2013 6:46 pm

There should be a liner in there and if so the hole should be centered on it. There are hole saws that can do the full size hole in one go.

McGiever · Post by **McGiever** » Sat. Oct. 05, 2013 6:52 pm

That would be a Diamond Core Drill Bit....best to rent that,$$$$$ Then there is the core drill machine...rent that also.
Hammer-drill is crude, but effective. YMMV

2001Sierra · Post by **2001Sierra** » Sat. Oct. 05, 2013 7:21 pm

If you have a tile liner drill its center.

Cap · Post by **Cap** » Sat. Oct. 05, 2013 7:22 pm

You do not need a diamond bit for cinder block. The purpose of diamond bits is to cut thru rebar in concrete. You can do that job with a star chisel & sledge hammer.

But if I am opening up a hole in clay flue, I'd try a hole saw on the end of a drill and/or gently break it away after knocking away the cinder block with a star chisel. You looking at 6" hole?

2001Sierra · Post by **2001Sierra** » Sat. Oct. 05, 2013 7:25 pm

Like on "Gold Rush" drill first

EarthWindandFire · Post by **EarthWindandFire** » Sat. Oct. 05, 2013 7:36 pm

I went and looked at the core drill at Home Depot. I might have to build a jig to hold the drill steady and straight while drilling. The chimney does have a clay flue liner. I'll try to stop the drill when I hit the clay, then I'll finish the hole in the clay with my Dremel. But, back to original post, which hole location would be best for maintaining strength, especially with so many intersecting mortar lines involved?

Post by **franco b** » Sat. Oct. 05, 2013 8:27 pm

I don't see where you have a choice if you wish the hole to be centered on the clay tile.

2001Sierra · Post by **2001Sierra** » Sat. Oct. 05, 2013 8:30 pm

franco b wrote:I don't see where you have a choice if you wish the hole to be centered on the clay tile.

Amen

Den034071 · Post by **Den034071** » Sat. Oct. 05, 2013 8:55 pm

Ole mason here .If you can fill chimney a foot above where you are cutting or drilling with sand yes sand the sand will absorve shock and prevent breakage .When you are done simply remove sand .Ive cut flues with just a brick hammer this way on the ground of course . Try it pm me if you need more info .jack

2001Sierra · Post by **2001Sierra** » Sat. Oct. 05, 2013 9:03 pm

Den034071 wrote:Ole mason here .If you can fill chimney a foot above where you are cutting or drilling with sand yes sand the sand will absorve shock and prevent breakage .When you are done simply remove sand .Ive cut flues with just a brick hammer this way on the ground of course . Try it pm me if you need more info .jack

One again experience! I love this forum.

tsb · Post by **tsb** » Sat. Oct. 05, 2013 9:35 pm

Use the sand idea if you can. Start with a star bit and hammer and make a small
hole in the center of the block. Enlarge the hole with a flat chisel to the size you need.
Then lay waste to the clay liner with the ball end of a hammer. Then grout in the liner.

McGiever · Post by **McGiever** » Sun. Oct. 06, 2013 7:13 am

Maybe I assumed wrong...thought it was a 90 degree photo rotation that happen here so often as folks don't know how to post them correct.

If I am correct...all 3 options are on the vertical center-line already.

EarthWindandFire · Post by **EarthWindandFire** » Sun. Oct. 06, 2013 7:39 am

McGiever is right, I didn't notice the picture was rotated incorrectly

My concern is not about centering the hole vertically, naturally the hole will be dead center, but whether or not I should smash a hole into a single block or move up horizontally and damage several blocks. It's hard to put this situation into words that make sense to others.

Cutting Hole in Cement Block Chimney.

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