Drilling through cinder block?

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Old 11-02-15, 02:06 PM
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Drilling through cinder block?

I need to install a clothes dryer vent through a 60 year old, 8" cinder block wall. The hole will need to be around 5" to 6" in diameter to accommodate the dryer vent.

Would I want to do this right in the center of the block, avoiding any corners, and what is the best way to accomplish this?

Thanks!
 
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Old 11-02-15, 02:12 PM
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The cheapest and easiest way to do it is to do a series of smaller holes in a circular pattern around where you want a new hole. It will and easy to break out the remaining block pieces. Depending on where you are going to put the whole in regards to the height of the wall you might be better off making the hole on a seam that way you would have a 4 block spanning across it above it instead of a joint. It's probably not going to make any different for strength but it would look better that way. Overall is a pretty simple project to do.
 
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Old 11-02-15, 02:14 PM
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IMO it's easiest/best to put it in the void portion of the block. I'd draw out the hole and then using whatever size masonry bit I had handy - drill a series of holes and then use a hammer.
 
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Old 11-02-15, 06:50 PM
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You will probably hit a cross web that runs between the inside and outside of the wall. On the old fashioned 3 core block, you could even hit 2 webs with such a large hole for dryer vent. 6" would be excessive for a dryer vent. You could drill a few test holes at the midpoint of the height of the block (4" up from the bed joint) to see where the vertical webs may be. The face shell of the block will be at least 1-1/4" thick.

I hope you do not have any of the old fashioned 3 core block that were used in CT from many plants.

I would drill the circular pattern of holes as suggested. A good starting point for the center of the circular pattern would be about 4" from the center of a vertical head joint..

Dick
 
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Old 11-03-15, 07:29 AM
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Yikes. Lots of terms I do not understand here. Lets go over some of this.

What is meant by 3-core? Three vertical cavities as opposed to what is normally just 2... is that it?

I am in Connecticut so this issue of 3-core blocks... is this a bad thing or just going to make my life more difficult?

If there are three cores would I want to go into the center of one side and hit one vertical as opposed to the center of the block and hit two verticals?

Vertical head joint? Again, I'm at a loss here.

I may be way off on the diameter of the hole. I'll need to source the vent kit to see what is really required.

As far as looks go... not a big deal. This will be located at the back of the building under a large car port just above and to the side of the oil delivery and vent pipes. Nothing pretty about it.
 
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Old 11-03-15, 08:53 AM
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If this is a foundation wall, I would make the hole for the dryer vent in the wood wall above the top of the cinder blocks and between the floor joists. Good luck
 
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Old 11-03-15, 09:02 AM
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What is meant by 3-core? Three vertical cavities as opposed to what is normally just 2...
Correct, you see them sometimes on older homes. I see them occasionally here in tenn also.
 
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Old 11-03-15, 09:25 AM
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If this is a foundation wall, I would make the hole for the dryer vent in the wood wall above the top of the cinder blocks and between the floor joists. Good luck
No, this IS the wall to the building. Have to go through this way or up out the roof and not wanting to go that way if I can avoid it.
 
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Old 11-03-15, 10:47 AM
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These are only examples. See next post.
 

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Old 11-03-15, 11:36 AM
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Ray - The 6x8x16 CMU is typical of some units since it can be laid by grabbing the center web and mortaring the ends. - Some people do not like the smooth ends because it can be difficult to keep the mortar on the ends (too wet or too dry) and prefer a 2 core unit with open ends and vertical mortar grooves on the "ears". - That is typical of just one of the many configurations available in North America.

Actually, there are many different configurations for a standard CMU because the specifications are so general and differences are personal and regional. Some of the variations are number of webs, core shapes (square and pear shaped), splitting grooves/guides and especially widened face shell tops and/or webs. One mold supplier to the industry has a catalog of over 1000 different molds for 8x8x16 "standard/normal" units and another for metric units. That is just for single units of one size but different units can be made with varying percentages of different shapes on a pallet. - That is why there is no just "standard" block for any wall thickness.

Dick
 
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Old 11-03-15, 12:23 PM
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Thanks, Dick. I have clarified my post.
 
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Old 11-03-15, 01:06 PM
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So based on the two photos it makes the most sense to drill the hole so that the outer diameter is just inside the end of the block. Perhaps 2" from the end.

That way no matter which style...2 or 3 core... is in there, the worst case will be I have to drill through one vertical " web" and maybe get lucky and not drill through any is it is a 2 core.
 
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Old 11-03-15, 02:00 PM
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You can test the left and right sides of where you want to cut the hole by drilling a quarter inch hole and seeing if it is hollow. If it isn't you can try adjusting left or right before cutting.
 
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