Drilling Concrete Block (Pillar Caps)


Old 11-08-06, 06:14 PM
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Drilling Concrete Block (Pillar Caps)

Need help - hoping to get pointed in the right direction with this. To some of you this might sound simple but since I haven’t done this before I wanted to get some advice before trying.

Had two concrete block pillars put in at the end of our driveway. The guy who built them ran an empty ¾” electrical pvc conduit underground from the house (about 10 ft away) and up through the center to the top of pillar #1. He then ran another empty ¾” conduit from the top of pillar #1 back down underground for about four feet and then up through the center to the top of pillar #2 in the event I ever wanted to have lights put on top of these pillars. Supposedly he cut the pvc conduit so it is just about flush with the underside of the pillar caps in both cases. Unfortunately he did not cut holes in either pillar cap, he just ran the pvc to the underside of each cap.

Well the time has come to install the lights on top of the pillars …but…. to get the wires to the lights that will be installed, I will need to drill a hole in the pillar caps which are made from concrete block that is about two inches thick (techo bloc brand). The questions are:

Should I make the hole in the cap only big enough for the wires to "just fit" through, or , should I make the hole big enough for the pvc conduits to fit through? What type of bit should I use…someone told me a dry masonry diamond core bit would work good for this but I wonder about starting the hole with the core bit since the ones I’ve seen don’t have a centering bit. What type of drill would be best to use, rotary or hammer? Would the hammer drill cause a higher chance for causing cracks in cap? Any advice would be greatly appreciated. Thanks in advance for your help.
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Old 11-08-06, 06:46 PM
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If it were me, I would remove the caps, determine the location of the conduit, extend the conduit, and drill a hole through the cap large enough to give me at least a 3/8" joint for sealant around the conduit. The light fixture will determine what the actual size of the hole is, and also determine the means to affix it to the cap. You should also fish the wire while the cap is off.
Old 11-12-06, 04:42 PM
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Thanks for input. Unfortunately when they installed caps they glued them on. Sure would have been nice if they would have left the caps loose. These things probably weigh about 200 pounds, probably didn't need glue to begin with. I guess the only option I have is to drill from the top. Any ideas that might make this go a little easier would be greatly appreciated. Thanks again for advice.
Old 11-13-06, 01:58 AM
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But. just exactly where is that conduit? I would start out by asking myself the stupid questions.

1: Where's the conduit? Answer: supposed to be in the middle.

2: How can I be sure? Answer: How bout drilling a hole.

3: What size bit? Answer: The smaller the better to begin with, start out with a 1/4-3/8" masonry bit and hammer drill it through the center.

4: This is just great, how the heck am I supposed to know if I hit the very center of the conduit? Answer: I dunno everything. Get creative. watch for gray plastic, look in there with a flashlite, use your air compressor and blow some air up from the other end......fish a brightly colored wire up from the other end......I assume the base of that lamp will allow the hole to be pretty forgiving.

go for it......


(There really are no stoopid questions. Stoopid answers....well, maybe)
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