How to cut 6" hole through concrete???

How would one go about cutting a 6" round hole through an 8" thick poured concrete basement wall? It appears that the only place I can get access to vent a stove out of our basement is to go right through the concrete. It's a great location for the stove, but not so hot to run a direct 4" vent setup outside.

I was hoping that the builder had stepped down the concrete level to match the slope of the outside grade from the front to rear of the house, but it appears that the concrete stays at the same height all along the side of the house. It's fully finished inside and covered with siding on the outside, but I'm using the opposite wall of the basement as a guide, and it is full height the whole way. I'll probe around this weekend and verify it's concrete behind it.

I do have a well stocked local rental place that I'm sure might have something that would do the job, as well as a proper dolly to move a heavy stove down to the basement.

Chris

The rental shop may be able to fix you up with a concrete core drill. It can bore a hole right through your concrete wall. Pretty fast, I might add. You may need a little water to cool and wash out the swag while you drill.

I have used long 1/2 inch rotary hammer drill bits to drill a series of holes and then a hammer and chisel to remove what's left. I first made a plywood template marking the large circle. I then used a wood bit to drill a series of holes in the template closely spaced. I bolted the template to the concrete wall and hammer drilled each hole. It was a lot of work especially the hand chiseling. For the cost of renting the proper large size core drill I was able buy a top quality hammer drill and bits. Would I do it again? Only as a last resort.

Yanche

hilti rents equipment thru home depot. see if they have a water cooled core rig. possibly the dd100 or 150. if your wall is smooth enough it will mount with the vacuum plate supplied with the rig. if not you can anchor it with a 1/2 inch drop in expandable anchor

Thanks for all the replies! I'll check out Home Depot here and see what they have, as well as my local rental place that I really like.

I was hoping not to have to resort to such drastic measures to get a vent outside, as boring a huge hole through the foundation is so, so , so PERMANENT. But oh, well, I suppose that it could always be filled back in with concrete down the road if necessary.

Chris

Don't forget to pitch it 1/8" per foot minimum IIRC.

Good luck!

On moving the stove, I took my front doors off and bin, and put the front of the stove towards the dolly, the legs just fit on the bottom of it. It worked great. If not, put a piece of wood to support the legs if possible. Run the strap around just above the stoker unit.

Hi Chris, I don't think you need a 6" hole, a 4" should be plenty, remember the outlet from the direct vent motor is only 4".

I'd wait until you see the unit, and can measure, calculate, re-measure etc.

A 6" hole would give you some extra 'wiggle-room' and of course you can pack fiberglass insulation in the gap around the actual exhaust pipe.

Concrete cuts pretty easy. Now, a field stone foundation wall, that's another matter. Hitting a black granite rock in the middle of a 16" wall, that is a challenge. I was using a small jack-hammer, and it took a lot of time to get through.

When I've cut or drilled regular concrete, it is relatively soft, and cuts/drills easily

Greg L

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LsFarm wrote:Hi Chris, I don't think you need a 6" hole, a 4" should be plenty, remember the outlet from the direct vent motor is only 4".

Hi, Greg. The plan was to make a 6" hole for a thimble setup which would also get me around the drywall on the inside and the siding on the outside. WNY has some nice pics of his vent setup at his old house that I was using as a guide.

I still may very well go the 4" pellet vent route so I can get a 'canned' system that comes factory sealed with gaskets, etc. Truly plug-and-play. Just a little $$$..

Chris

Chris,

I core foundations all the time for wood/gas/coal installations. The coring bits work the best. Be sure to save the "plug" of concrete to use as a patch if you decide to remove the stove in the future. The plug can be epoxied back in pretty easily, and will look nice too.

Mike

Complete Heat wrote:Chris,

I core foundations all the time for wood/gas/coal installations. The coring bits work the best. Be sure to save the "plug" of concrete to use as a patch if you decide to remove the stove in the future. The plug can be epoxied back in pretty easily, and will look nice too.

Mike

Thanks! I'll go in search of a core drill for rental and do it that way, and save the plug as you mention. I like things that are reversible. Makes life easier if the potential buyers of the home in the future have no interest in a stove.

Chris

Do typical concrete foundation walls have rebar? More than likely they do. If you do find a rental unit, it'll be diamond bit. If You if go the star chisel and sledge rout, have a sawzall available to cut any steel.

I burrowed thru a few walls in the past to run large pvc & foam insulated copper tubing we call X-50 used in the cryogenic industry for liquid nitrogen in food plants. Make my arm sore just thinking about it!

I had the 6" metal duct around the 4" since it was a combustable wall (wood) so you have an air gap as recommended. If you have a non-combustable wall ie) concrete, I don't you need to make it that large.
Just my 2 cents.

coaledsweat wrote:Don't forget to pitch it 1/8" per foot minimum IIRC.

Does this pertain to the amount of angle you need to ensure the coal flows from the outdoor bin and into the coal hopper on the boiler? How do you determine the angle or pitch, and can the core drill be set to that angle?
Thanks!

crmoores wrote:

coaledsweat wrote:Don't forget to pitch it 1/8" per foot minimum IIRC.

Does this pertain to the amount of angle you need to ensure the coal flows from the outdoor bin and into the coal hopper on the boiler? How do you determine the angle or pitch, and can the core drill be set to that angle?
Thanks!

No, we are talking about the smokepipe from the stove. Horizontal runs must have some pitch, the more they have the better.

For coal to flow as a chunks, the angle needs to be about 45* or better (for coal bins).

Depending on the core drilling machine, it may have adjustments for angles or you may have to shim and/or clamp it. I would not attempt to use a 7"core drill half way up a concrete wall.