Cutting Concrete Block

Mossyoakglock · September 26, 2011

I need to cut a piece of a concrete block wall out in our garage. I need to cut 3 inches off the face of the wall/block that is about 7ft long making a sort of pocket in the wall. It will probably be about 14" off the ground and the cutout will be around 10" tall. I'm going to put a piece of steel across the top to help support and distribute the weight as well.

What is the best way to cut this? I can't rent a concrete saw from Home Depot since I don't have the space to use it. Would it be better to get a diamond blade for a skilsaw or for an angle grinder?

Any other thoughts or methods somebody can suggest?

desrtrat · September 26, 2011

if you can find a 7 1/2" worm drive saw will work better than a regular Skil. a blade for cutting concrete is always best. have a hose with water to keep the blade cool, and you'll be ok. you'll need a bunch of extra blades..

good luck

GasHog369 · September 26, 2011

For that long of a cut, buy yourself a diamond cut blade. The standard composite blades will wear down extremely quick and will take much much longer. Whichever skil saw you use, make sure dont care much about it or need to depend on it in the future..

Most likely you will burn it up pretty good and throw it out of alignment..

Also you will need to look at the max cutting depth of the circ saw.. Depending on what size blade you have, it may not get all the way thru.

Personally i would find a way to get a concrete saw to fit in there, and or rent a rotary hammer with a chisel on the end, use the circ saw to jsut score where you are going to cut , and finish with the rotary chisel..

I also agree that when cutting , keep plenty of water on the block / and blade at same time. Also goggles and a respirator would be a great idea. If u dont have a respirator, use a face shield of some sort and you do not want to breath in all that dust... Been there, done that.

jdubya · September 26, 2011

+1 on the diamond blade.

You could also put a diamond blade onto a 4 1/2" grinder to make the cut. It may be a little easier to handle than the circ saw in a odd position.

Also, if you are going to use water as suggested, please plug the powertool into a GFCI outlet or threeway splitter. SAFETY FIRST.

music · September 26, 2011

Are you talking about cinder block? If so, I'd take out whole blocks at the joints, and fill-in/fit to the new header from the block line. A chisel works fine. Maybe I didn't understand?

Mossyoakglock · September 26, 2011

Yes, it is a cinder block wall with a regular wall (2x4s and drywall) on top of it. I attached a very crude picture from paint so you can see kinda what I want to accomplish.

Porter_ · September 26, 2011

i'm sure you know what you're doing, so i won't preach...but if it's a load-bearing wall make sure you're not weakening it to the point of failure. just keep in mind that that wall may need to transfer dead load, wind load, snow load, etc. to the ground.

GasHog369 · September 26, 2011

Being that it is cinder block, I dont know how you are going to accurately and delicately cut in 3"and then chip along the back side of the pocket without knocking out the rest of the block..

Why not remove the whole blocks, then replace with smaller bricks that are not as deep and re mortal them in, to resupport the wall again. Also a lintel should be installed to carry the load...

I also agree with what is said above about temp support braces while you are doing this work. I would use build a temp beam out of minimum 2x6, if not 2x8, then support the beam going to solid ground using also 2x6 / 2x8's. Wouldnt be a bad idea to sister them together with glue and nails. I hate to preach about this like PORTER did not want to do, but he brought up a great point that should not be bypassed or assumed the wall will hold or the roof wont collapse.

Mossyoakglock · September 27, 2011

My thought was to make the cut and support it while working then put in a piece of angle iron to support the weight and then backfill in the holes with concrete. My thoughts about cutting 3" off the cinder block are the same. That's why I thought I'd ask before just cutting away.

There is already a 2x4 or 2x6 that runs along the top of the concrete wall sandwiched between the blocks and actual wall. I would not touch this piece. I would probably put the steel/iron underneath this for added support.

I might just give a concrete and coring company in town a call and see if they give free estimates and see how much they will charge.

I don't mind doing this kind of stuff and am comfortable doing repairs, etc but seeing that this might be a little more involved and require more/specialized tools than what I have this might be a job for somebody else.

GasHog369 · September 27, 2011

Wouldnt be a bad idea to call in someone professional at all

Why are you creating this pocket in the wall anyhow?

music · September 27, 2011

Wouldnt be a bad idea to call in someone professional at all

+1. I pretty much know how I'd do it, but can't (won't) attempt to explain it on a forum for fear of making it sound easier or simpler than it is. I've built a few houses with my dad (who built for almost 50 yrs), have lots of tools, and have a good "feel" for it. It's not possible to describe in words, without seeing it all first hand. Heck, those TV shows that "show you how" don't show you how... they just give a snapshot version, without all the sweat and cut hands.