Coring through my foundation wall; a few questions

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Old 06-02-15, 02:50 PM
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Coring through my foundation wall; a few questions

I'm running a sewer line from an outbuilding in my back yard and need to core through my foundation wall in my house. I figure the hole will be about 40" below grade, just above the footer. I understand the trenching/sloping of the sewer line, but I never did the boring before and wondered what I should be aware of? Thought I'd rent an electric core drill and a bit from a local rental place. Some of the things I'm wondering about are: 1) isn't there rebar in my foundation wall? How do I avoid that? (house was built in 1954, if that helps). 2) I was planning to bore a 4" hole for a 3" PVC sewer pipe (sound about right?) 3) I wanted to place a smaller pvc conduit in the same trench to run a coaxial or CAT5 cable to the building...can I also bore a smaller 1" hole near the original 4" hole, or would that weaken my foundation wall too much? I have bentonite soil, so there is sometimes movement in my foundation when the weather is wet.

I would very much appreciate any info anyone has on this, so if anyone has any words of wisdom, I'm all ears! THANKS!
 
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Old 06-03-15, 05:02 AM
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I've always used a rotary hammer. I bore a ring of holes through the wall using the hammer drill function then switch to hammer only with a chisel point and knock out the center.

In my area code requires a conduit or sleeve where a drain line passes through the foundation wall. That sleeve get's mortared in place then the drain line passes through it. Both the conduit and any angle of your drain line means the hole in the wall will have to be rather large so keep that in mind if using a drill (coring bit). I generally use a section of 6" PVC pipe for the sleeve. Making a smaller hole in the wall may seem easier but it can be a real headache to get your drain line to properly align so some free play can make it go a lot easier.

Yes, you may have rebar in your wall. You won't know until you hit it.

Your Cat5 conduit depends on how you make the hole in the foundation. If boring the hole then I'd do a separate hole about a foot or more away from the drain line hole. If using the hammer drill and chiseling out the center I'd make a "mouse hole" to run the Cat5 conduit next to the drain line sleeve.
 
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Old 06-03-15, 05:24 AM
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I've cut some deep, long, straight lines through concrete and right through the rebar, but I don't recommend it. Slows the cutting and eats up an expensive diamond blade. Our cuts were also water cooled so not sure if your basement would need or accommodate that.

I prefer Pilots solution as filling back in around that sleeve is simple and then water sealing the outside doesn't care if it was a really neat hole or not. If you run into any rebar, just chisel around it and then cut with a grinder or other. Having plenty of space makes work easier. Then run your smaller conduit through the same opening between the sleeve and the concrete.

Not a pro, just been there.

Bud
 
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Old 06-03-15, 07:20 AM
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Renting (or borrowing) a pachometer makes short work of locating embedded rebar in concrete. The more sensitive ones will locate a No. 4 bar as deep as 6" below the surface, but their cost usually puts them out of reach of most people. The cheap (less than $100) Zircon that I bought about 10 years ago will only scan to about 3" deep, but its audible feature is effective in finding most rebar up to that depth.
 
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Old 06-03-15, 12:30 PM
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Thanks everyone!....as usual, great info and I appreciate it very much!
 
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Old 06-08-15, 01:26 AM
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don't bother coring - use the rotary hammer approach,,, the size hole you'll need is too large to core using a weka-style hand-held drill,,, setting up a drill stand's the only other way to do it,,, my bet is you won't find steel but, even IF you should,it won't be difficult to cut,,, the chances of your running into edge steel are nil,,, should you encounter some rebar, this is sound reason to buy a sawzall

think we only used the pachometer 1 time when we were coring a jfk runway elevated over the sound into post-tensioned conc slabs,,, even then it was eic & gc located

gl
 
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Old 06-09-15, 07:15 AM
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OK...also good to know since I don't think I'll have room in the trench (or a real stable way) to set up any kind of drill stand. The more I hear about this, the more I like Pilot's rotary hammer approach. I assume for a 4 or 5" hole, I'd drill something like 10 or 12 half-inch holes then (as was suggested) switch to hammer-only-mode and chisel/impact the areas between the holes to knock out the plug. Does this sound about right???
 
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