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Outbacker 03-07-2009 11:14 AM

Precautions when cutting concrete
I am going to be cutting a 12X12 inch square hole in a concrete slab to accommodate a drain box, and was hoping to get some cutting tips from you who have done this before. I am going to get a diamond blade for my circular saw and cut the hole. Which blade is better :wet or dry? I guess with wet I would keep the area wet with a hose trickling water out. Am I correct? What about depth of cut? I cannot see going 3 inches all at once. How deep should I set the blade for each cut? Any precautions to follow when doing this (outside of the obvious of gloves, eye safety gear, filter mask)?


hondadrv24 03-07-2009 08:53 PM

I would just go ahead and rent a gas powered wet saw from a rental company. You can do it with the circular saw if you want but make sure you have water on it to keep the dust down. Concrete dust does nasty stuff to your lungs. Check around for prices on renting, I think when I was looking to rent a saw it was like $50 for a day. so probably 20 for a couple hours. Money well spent imo. If using the circular saw i would probably set it like you suggested to cut through in 2 passes. Just be careful and keep the dust down

Daryl in Nanoose 03-08-2009 09:47 AM


jdougn 03-08-2009 12:14 PM

Yeah, I would cancel the idea of using water with an electric powered circular saw. That is an extremely bad mix.
Renting a gas powered concrete saw is a real good idea or just using your circular saw dry. If using the circular saw, the saw itself will let you know how deep to cut. When it starts pulling too hard then lighten up. If you go dry, keep in mind there will be massive amounts of abrasive concrete dust to control. If you have the budget then consider renting an electric "chipping hammer" which is like a mini Jack Hammer. If not, then get a good concrete chisel and hammer. The 12" square will have to come out in pieces unless you overcut a whole lot.
hth, Doug

CraigFL 03-09-2009 05:35 AM

And... your circular saw will be finished(dead & gone) by the time you finish with the hole... They really aren't made for that kind of cutting and duty cycle.

jdougn 03-09-2009 07:24 AM

I've used my DeWalt circ saw, purchased new in 1994, a number of times to cut either brick or concrete and it's still going strong. But, CraifFL is right, concrete dust will tear up bearings, bushings and moving parts.

Outbacker 03-24-2009 06:01 PM

Thanks for the replies and precautions. I was looking at the diamond wheel blades, and the ones I was looking at can be cut dry. I will do that and take shallow cuts till I get a good groove in the concrete and then just break it up with a masonry chisel. The saw I am using is old and if it does pack it in, then it is no loss. I figure if I take it easy with shallow cuts it should work.

Quattro 03-25-2009 12:11 PM

Worried at all about rebar?

I'm considering doing something similar where my driveway (very large, concrete) meets my foundation wall. I'd rather have 3 feet of gravel or garden along the I'd have to somehow cut and remove all that concrete (about 30 linear feet along two walls).

Outbacker 03-25-2009 01:06 PM

In your case, I would rent the gas powered concrete cutter, and ask the rental guy about the possibility of rebar. I am cutting a small square, and I doubt there is any rebar in there as it is only a back door patio slab. I was quoted about $120.00 to rent the cutter and buy a blade, so I am going to buy a diamond blade and use the old circular saw and see how it goes.

yesitsconcrete 03-27-2009 06:36 AM

if it were my job, i'd rent a gas power'd demo saw w/14" blade,,, it'll cut 4" deep & you can rent the blade & pay according to the damage/useage :rolleyes: some even have wtr hookups for blade help & dust control,,, always easier to make the 1st cut 1/2" deep STRAIGHT then cut another 1" at a pass.

we have milwaukee gear-drive circle saws but they're fitt'd w/dustmuzzles to make things easier, cleaner, & save bearings/motors.

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