What's the best way to punch a 2" hole for a drain pipe through a cinder block wall?
I've researched a variety of suggestions from a hammer and a star drill, to drilling a ring of small holes in a circle with a carbide bit to renting or buying a diamond tipped core bit. What's the best way of doing it so as NOT to crack the block?
I have used them all. FIrst of all, I am sure you don't really have a cinder block wall. Many people wrongly call concrete blocks, cinder blocks which were made from coal cinders. Making a hole in real cinder blocks is easy, they are soft and can be punctured without much effort. Now concrete blocks are different, they are hard and brittle.
You can use any method and it will not crack the block unless you use extreme force to do the job. The easiest is to rent a large drill and bit from your local big box store. The hardest part is to find out if you have two core or three core blocks. New walls will be 2 core. Whatever method you use will work best if you miss the web in the block. You may have to do some small hole drilling to find the core and web. Old blocks with 3 cores are easy to work if you drill through the center and hit the center core. Newer blocks will only have two cores and you will hit the web if you drill in the middle, so you need to drill 1/3 of the way from the end. The year that manufacturers changed to two core blocks will vary according to when they changed machines and moulds.
Yes, vertical re-bars mortared in the cores, sometimes from footing up to the sill plate, can cause problems. You may want to check with a metal detector to see if you can find any. Horizontal reinforcement would most likely be in the mortar joint, so avoid penetrating in this area.
Excellent points. The worry about 'crackign the block' is no biggee. The likely hood of making a tight fitting 2" hole without using a core drill is zero so it will have to be patched in any case. I have done the BFH route and patched the remains later, used a 3/8" hammer drill and small concrete bit and probably a few other methods. If I ever have to do it again it will be 'rent a real electric hammer and decent bit, drill a ring of holes and knock out with hammer' Of course being careful to miss the web.
Yes I did. But I own neither. I probably should have added that I would prefer a solution that would work with a run of the mill, 1/2" AC power drill that I do own.
You are probably correct. It has the very rough and granular texture I associate with cinder blocks, but I'm not quite sure how to tell the difference without a hardness tester.
House was built in the midst of war shortages in 1942, if that helps. There's also a section where the block has heaved so I can get a better idea what I am dealing with by inspecting that section of the wall. I believe it's open enough to make the two/three determination.
Well, if my previous experience of trying to drill through to the basement and managing to hit a discarded hammer head inside the wall cavity is any indication, I'll run into something nasty. Acutually, now that I am reading through this, I realize there's a dryer duct installed that I can pull that should give me a better idea of what I am facing. Thanks for the input.
A good idea, but I'm betting there's no rebar because everything was in short supply in 1942. They skipped on things like putting building paper between the subfloors so the open basement ceiling rains down plaster dust on the stuff below. Such an easy thing to have done right during construction and now such a bitch to remediate.
So far, it's a once in 25 years job so I think HF might do the trick. I will have to cut some smaller holes to mount an HDTV antenna and rotor in the next few weeks, but after that, the block wall should be safe for another 25 years. Thanks!
You might try a 2" metal hole saw. They should be available at the box stores and don't cost much. Here's a quick hit on a 2.5" hole bit for $15.00.
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As for 1/2" drill, should be no problem - they should run at a MUCH slower speed than when drilling wood.
OR
You could just poke an ugly opening, insert a 2.5" bit of PVC, then fill the void up with cement.
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