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rjordan392 07-22-2008 03:39 PM

Drilling Through Concrete Wall
I was advised on another forum not to drill a 4 inch hole in my concrete wall if it does not have rebar. I did not get an explanation why. I would like to add another vent hole close to another existing vent hole in this wall and wanted to know if there is a code requirement as to the distance between holes. For what its worth, I don't know if I have rebar. My home was built in the early 50's. I checked out 60 homes in my back driveway and 19 had holes drilled for vents through the concrete wall. About 20 homes had vents installed above the concrete wall and through the brick. The rest of the homes had no vents. None of the homes with vents through the concrete has shown any deterioration on the walls.
What are the problems with or without rebar?

Termite 07-22-2008 04:19 PM

I don't see any issue with drilling a 4" hole in a concrete foundation, provided that there is at least a foot of concrete over the top of the hole, and provided that the hole is a foot or so away from the other hole.

Rebar simply keeps the concrete from moving too far when it inevitably cracks. A hole could theoretically weaken the concrete and create a stress point, but it is a small hole. They often cut entire windows into concrete walls with no ill-effects.

rjordan392 07-22-2008 04:47 PM

I am bringing my vents (two) up to code. I just learned that my existing setup with two vents (bathroom and Gas dryer) going into a wye connector before exiting the dwelling is not code approved and that each should have their own vent.

Termite 07-22-2008 09:12 PM

Oh good golly my heart just stopped for a second. :no:

You definately have a dangerous installation there, as the combustion gas from the dryer (carbon monoxide!!!!!!) definately needs a dedicated vent.

Glad to hear you're taking care of it. :thumbsup:

rjordan392 07-22-2008 09:46 PM

I had a backflow preventor placed on the bath vent duct to prevent air from the dryer from backing up into that duct. The dryer is only a few years old and the combustion is good so far. So I will make corrections this week.

yesitsconcrete 07-23-2008 06:35 AM

either diamond core the hole or hammer drill series of holes on the circumference & punch out the core,,, if you run into steel, move the hole if using the hammer drill,,, coring can cut the steel,,, coring isn't easy for a diy-er - suggest hammer drill & 3/4" bits.

rjordan392 07-23-2008 10:31 AM

Thanks for the tips.
I already used a core drill with a diamond bit. It took about 30 to 40 minutes to go through 9 inchs of concrete. The tool rental and diamond bit only cost $70.62 for 4 hours. I returned it in less then 2.

yesitsconcrete 07-23-2008 10:50 AM

good for you,,, just curious,,, wet or dry & did that price include wear on the bit ??? for that thickness, we wouldda done it by hand w/weka 3speed 110v drill made by the germans

rjordan392 07-23-2008 06:30 PM

I drilled dry. The price includes everything including the tax. I rented from Home Depot. The drill hammer was a "HILTI" 1-3/4 SDS. I used a small worktable to rest the hammer drill on as it was too tiresome to hold it.

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