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Old 10-25-2010, 03:05 PM   #1
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cutting concrete with circular saw


i need to demo some concrete to run plumbing for bathroom on slab. I was going to rent a diamond concrete saw & jackhammer, but the concrete saw is $150/day.

So I thought I can save some money and use a diamond blade with a 7" circular saw to score it, and then jack hammer. I remember seeing it done on a DIY show.

Anyone done it this way before? Is it a good idea?

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Old 10-25-2010, 03:24 PM   #2
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cutting concrete with circular saw


Depending on how many feet you need to cut, I would think it could be done in half a day. Can you rent for half a day for $75.
I would think a good blade would cost at least that much, not to mention the wear and tear on a circular saw. When I use a wet saw indoors, set up plastic as walls and 2x4 caulked down to the floor to create a dam, use a wet vac to suck up the water that does not go through the floor (the cut you are making)
The dust would be unbelievable inside a house without using a wet saw.
I would not use water with a circular saw .

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Old 10-25-2010, 03:34 PM   #3
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cutting concrete with circular saw


I would look around a little more for an electric cut-off saw. Here, a gas or electric is only $50-60 per day, and I think the electric are on the cheaper end of that. Plus, they're FAR safer to use indoors.

The circle saw will only cut to about 2" deep, at best, where the cut-off saw will cut down to 5" if it's a 14" saw. I would estimate that it will take 10-15 times longer to cut the 2" with the circle saw than the 3-4" with the cut-off.

If you're looking to save the money, I'd just pass on renting the jack hammer. If you can saw all the way through the floor, it should break fairly easily with a simple sledge hammer.
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Old 10-25-2010, 03:59 PM   #4
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cutting concrete with circular saw


sds, good idea on the plastic on walls.
i got one of these $14 blades at lowes.

i will keep looking. but so far, 3 tool rental places here charge about the same.
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Old 10-25-2010, 04:25 PM   #5
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cutting concrete with circular saw


Angle grinder with a diamond blade to get the first inch or two might help.
If you have a hammer drill, some holes would also help.

Be prepared for lots of dust either way.
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Old 10-25-2010, 04:48 PM   #6
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cutting concrete with circular saw


You can demo concrete that is relatively thin (4 inches or less total thickness) without scoring first with a diamond blade. The only downside is the cut is ragged, but you are going to patch it anyway, so perhaps that is not an issue. And you certainly can cut an inch or so with a diamond blade on a circular saw, I recently did just that in my basement when I put in some drain lines under the basement slab.

My slab was only about 3 inches thick, I scored it with a masonry blade (could have used diamond), then jackhammered the concrete out with a demolition hammer and a chisel bit. It worked fine.

I also recent cut several concrete blocks with a diamond blade on a circular saw, again it worked fine, just make sure each cut is small (say 1/2 to 3/4 inch depth). Also, be sure to wear a NIOSH approved mask (I have a mask with a combination chemical and airborne filter), as concrete dust is extremely hazardous to your health.

I did my cutting outside, so I did not need to wet it down, if you cut inside you may want to dampen the concrete prior to cutting, else the dust will get everywhere.
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Old 10-25-2010, 04:53 PM   #7
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cutting concrete with circular saw


How many feet of cut do you have to do Ace?
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Old 10-25-2010, 05:05 PM   #8
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How many feet of cut do you have to do Ace?
the bathroom is about 6'x10'. Almost all of it needs to be opened up, so about 25' to 30' of cuts.
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Old 10-25-2010, 05:20 PM   #9
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cutting concrete with circular saw


For that amount of cutting, especially indoors, I'd still suggest one of these:

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The electric motor is protected against small amounts of water, which is all it will see when sawing with a sprayer or trickling water hose.

I wouldn't run water with a circle saw, as they're not intended to be run in water.

If you dry saw in your basement, you could spend countless hours cleaning up the dust, where wet-sawwing is very easy to attain.

A jack hammer will create small amounts of dust as well, and will leave an inferior edge to patch into.
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Old 10-25-2010, 05:28 PM   #10
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I've done it ----Daniel is right,though--If you are going to tile,just jack hammer without cutting--

Back to the saw----I used a Skill wormdrive,a diamond blade and a garden hose---

Make absolutely sure you plug into a gcfi protected outlet--set the garden hose to a trickle (I had a spray nozzle) Hang the extension cord from the ceiling so it stays dry--

Cut--keep the water trickling onto the blade.---I cut over 50 feet and the blade looks almost new.

---Mike---
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Old 10-25-2010, 05:28 PM   #11
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cutting concrete with circular saw


Back when I was a Rookie... had to chop out some concrete for a 6 x 10 bathroom in my own home...

No problem.

Borrowed the gas powered 14" saw from work, closed the door and let 'er rip.

Wow! was there a dust cloud in there...
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Old 10-25-2010, 05:30 PM   #12
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Looking at Cresco Rentals in SF a 14” saw rents for $50 for 4 hrs. and $75 a day.
http://crescorent.com/bl_san_francisco.html

Even with a diamond blade 30’ is pretty tough on a circular saw.
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Old 10-25-2010, 07:29 PM   #13
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Looking at Cresco Rentals in SF a 14” saw rents for $50 for 4 hrs. and $75 a day.
http://crescorent.com/bl_san_francisco.html

Even with a diamond blade 30’ is pretty tough on a circular saw.
thanks! i did not know about that company. Those are much better prices.
I think I might have found a rental place that's cheaper still. $35 for either elec. or gas for 4 hrs, probably no blade included. I'll have to give them a call in the morning.

kinda off topic, but:
i see cresco has concrete chain saws. I need to cut the top of a footing to open up a doorway from a 32" door to 6' opening. The wall is load bearing and sits on top of footings raised above the slab. There is already a 3' opening for the existing door, so I will just need to trim about a 1.5' on each side off. Of course I am installing properly sized headers for the wider opening. I was thinking using the chain saw because the concrete cutoff saw will not be able to cut deep enough. It would be nice if I can rent one tool for the both jobs, but not sure if I can. Any thoughts?

Last edited by acerunner; 10-25-2010 at 07:40 PM.
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Old 10-25-2010, 07:36 PM   #14
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That kind of cutting is a saw killer---I used my least favorite saw for that one---Mike--
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Old 10-25-2010, 07:48 PM   #15
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cutting concrete with circular saw


Yes, you can use the same saw to do both: The electric cut-off saw.

If you have access to both sides of the wall, the cut-off saw will work great.

If you want to cut the entire opening from the outside, with no overcutting in the corners, the chainsaw is better.

You DO NOT want to cut the floor with the chainsaw, or even think about running it inside. The chains are expensive and slow, and the saws use a very rich fuel:oil mixture, bad enough that it sometimes chokes me out when running ours outside in a hole in the ground.

Just for the record, I own at least one (in some cases 4 or 5) of everything mentioned in this thread so far, and I'd recommend the 14" electri cut-off saw.......................






And another side note: The last time I used a gas saw inside a house I thought I killed an 80+ YO man. I warned him to leave, go for a walk or something, for a while as I cut. I guess he came back before I was done and took a nap on the couch. I'll tell you when I came up the stairs from the basement & saw him hunched over, I finally realized how unsafe running a gas saw in a house was. There's no reason to risk it when you can get the same results from a safer, leaner approach.

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