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Cutting driveway slab to install drainage channel

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  1. #1
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    Default Cutting driveway slab to install drainage channel

    Hi everyone,

    I am having drainage issues during heavy rain across the front of the garage. I'm on a sloping block and the existing drainage can't cope with moderate to heavy rain. We are in a very leafy area so the drain and pipe often gets blocked by dirt and leaf litter.

    My plan was to install drainage channel (the poly everhard stuff) across the front of the garage and down the side of the garage. Will need 4m cut across the front of the garage and about 9 metres down the side. The channel down the side is to replace the current narrow pipe (its smaller than 90mm).

    I have tried cutting with a 230mm diamond blade in the circular saw but it is extremely slow going. I'm cutting 10mm at a time and the saw is moving through smoothly but slowly. The saw can also only cut down to 85mm and the slab is 100-125mm thick.

    After wisdom on the best method for cutting the concrete:

    a) persist with the saw and use a rotary hammer drill to remove the waste (is the 85mm depth sufficient to remove the concrete without damaging the rest of the slab?)

    b) hire a concrete saw from Kennards (but don't know how long I would need to cut this length as it says it cuts at 25mm intervals)

    c) get a tradie in to cut it (much faster but much more expensive)

    Thanks

  2. #2
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    Ring a concrete cutter and ask them how much per m for a road saw. They are pretty cheap.

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  3. #3
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    Quote Originally Posted by pseudodog View Post
    c) get a tradie in to cut it (much faster but much more expensive)
    Have you tried them as they are pretty quick and from my experience well worth the cost.

  4. #4
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    Without a doubt, ask as to cost for a concrete cutting business to do the job,
    and also ask how close they can cut to a wall because the partner (hand) saw can get to withing about 50 mm but the large road saw may be further away,
    if that is going to be a problem.

  5. #5
    Deactivated User Marc's Avatar
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    Doing it with a 9" grinder is a recipe for disaster. You can do it with a hired petrol concrete cutting saw if you have the arms and back to handle them, or you can take a gamble and buy a chinesium one. For a one off job they can be a solution, I have seen them for $380 to $500, as opposed to 1500 - 2500 for a good one. Once you finish, put it on Facebook Marketplace for half price and get rid of it.

    But the obvious choice is a concrete cutting business. Plenty independent one man operation in most suburbs. Cost? I don't know, last time I used one was ten years ago and I thought it was cheap, but cheap and expensive are very subjective concepts
    Some folks believe that paying the local GP $10 for a gap payment is a "rip off" others find a piffy electric car that needs recharging every 200 K and cost $60,000 a bargain. Go figure

  6. #6
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    A road saw is quicker and cheaper than a hand saw if you have the room.

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  7. #7
    Senior Member YoungBolt's Avatar
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    Quote Originally Posted by Marc View Post
    Doing it with a 9" grinder is a recipe for disaster. You can do it with a hired petrol concrete cutting saw if you have the arms and back to handle them, or you can take a gamble and buy a chinesium one. For a one off job they can be a solution, I have seen them for $380 to $500, as opposed to 1500 - 2500 for a good one. Once you finish, put it on Facebook Marketplace for half price and get rid of it.

    But the obvious choice is a concrete cutting business. Plenty independent one man operation in most suburbs. Cost? I don't know, last time I used one was ten years ago and I thought it was cheap, but cheap and expensive are very subjective concepts
    Some folks believe that paying the local GP $10 for a gap payment is a "rip off" others find a piffy electric car that needs recharging every 200 K and cost $60,000 a bargain. Go figure
    What's wrong with an 9" grinder?
    I've used them a few times and still am in one piece today!

    I wouldn't recommend it for everyone, but if you've handled anything fairly dangerous before (e.g. a chainsaw) then you should be fine. Just stay out the way of the damn machine incase the f**ker kicks back. I've done more jobs than I probably should have with my $80 ozito 9" grinder and i'm yet to have even had a near-miss or any kickbacks. The only problem with a 9" is how long it can take to spin up and wind down which if you're stupid can cause you some problems.

    OP - you can buy 9" grinders for as cheap as $100. It's a one time use, likely will use it for 10min max. Why spend $300+e for a concreter to do it. Trying to get a creter to come and do the job will be half the challenge as it's no money for them and half a day wasted.

  8. #8
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    Quote Originally Posted by YoungBolt View Post
    What's wrong with an 9" grinder?
    OP - you can buy 9" grinders for as cheap as $100. It's a one time use, likely will use it for 10min max. Why spend $300+e for a concreter to do it. Trying to get a creter to come and do the job will be half the challenge as it's no money for them and half a day wasted.

    Quote Originally Posted by pseudodog View Post
    Will need 4m cut across the front of the garage and about 9 metres down the side.

    So you think you can cut 17 meters of concrete driveway with a 9" grinder in 10 minutes ?

  9. #9
    Deactivated User Marc's Avatar
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    YB, your post is not only inaccurate and misleading but outright dangerous advise.

  10. #10
    Community Moderator phild01's Avatar
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    pseudodog, do not start your angle grinder experience with a 9" grinder.

  11. #11
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    Quote Originally Posted by Marc View Post
    YB, your post is not only inaccurate and misleading but outright dangerous advise.
    I agree they are decidedly dangerous which is why the have been banned from a big proportion of industrial sites.

  12. #12
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    Job all done. $550 for bit over an hour of work. Already chiselled away 1/3 ready to install drainage.

    I had considered going for the large grinder but it was too much of a jump in size compared to the usual angle grinder I use. Not worth the cost of a grinder and the risk.

    Thanks heaps for the replies.

  13. #13
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    Quote Originally Posted by pseudodog View Post
    Job all done. $550 for bit over an hour of work. Already chiselled away 1/3 ready to install drainage.

    I had considered going for the large grinder but it was too much of a jump in size compared to the usual angle grinder I use. Not worth the cost of a grinder and the risk.

    Thanks heaps for the replies.

    Road saw?

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  14. #14
    Senior Member YoungBolt's Avatar
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    Quote Originally Posted by Marc View Post
    YB, your post is not only inaccurate and misleading but outright dangerous advise.
    In what way?!

    I’m not suggesting that a 9” grinder be used for long periods or to cut up steel/concrete standing upright.

    A 9” grinder is as dangerous as a demo saw yet everyone here is happy to suggest using one of them. I once worked for a major manufacturer of petrol power tools which includes chainsaws and demo saws. The petrol demo saw killed more people than chainsaws ever did and we were always in and out of litigation over the saws. The issue wasn’t the machine, it was the careless operator not being conscious of using it in a way that when it kicked back you were in The way of it. Those demo saw carts did little decrease the danger of the demo saw as well because again when it kicked that thing went flying and often in the path of the operator who is actually standing my right behind it.

    I’ve used a 9” grinder plenty of times, and so too have my friends and family members. We’ve all still alive and healthy.

  15. #15
    Deactivated User Marc's Avatar
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    YB, if you think that it is a good suggestion to use a 9" grinder to cut 17m of drainage, (that is actual 34m of cut), with a 9" grinder crouching down, by someone who has never used it ... I can't help you.
    A wet concrete saw is dangerous like most power tools are, but is the correct tool for the job. Cutting that amount of concrete with a grinder is like cleaning a toilet with a toothbrush, using your left hand and walking backwards whilst looking in a mirror and having a sneeze attack.

    And to add that you and your family use 9" grinders regularly and are yet unharmed is rather disingenuous.

  16. #16
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    I've used a mate's 9" grinder to cut a square in concrete for a post hole, no worries, and my mate is big into steel work and uses it a lot, maybe thousands of times, but a couple of years ago he got careless, the disc caught and shattered and a big piece lodged in his upper lip. Goggles and face shield are always nearby now

  17. #17
    Deactivated User Marc's Avatar
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    My point is ... the right tool for the job. If you donít own one, rent one. To suggest a grinder for 34m of concrete is like suggesting a multitool, to rip a 2Ē 6m plank in half. Want more illustrations? Walking to Rome from Sydney ... Digging a house footings with a spoon ... blowing in your boat sails to change direction... keeping the smell of a fart in a basket ... etc 🤪
    Yes, i have a Makita and a DeWalt 9Ē, and use it when it is appropriate. A hole in concrete is a sensible use, grinding I beam joints or rust, done many times. Cutting large boulders into marbles? Not a good idea

  18. #18
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    I've done something similar recently with GMC circular saw, and am happy with the outcome, although total cut was only about 6 metres. I'd never cut concrete before. Things i learnt:

    Try to use very slow water on the cutline to keep the dust down and seems to make the blade work better;
    Don't waste your time with rotary hammer drill. I bought a $130 used demolition hammer (originally about $200 from Aldi) and it has done a great job. Eats the concrete.
    Use ear muffs, face mask for dust, safety glasses and use a knee pad so you can get comfortable on the cut line. Don't rush.
    Do a number of cuts. First one half inch. drop the blade, do again, then do again. I was cutting through 3 inch slab, no problem. And the demo hammer knocks out the last bit. You don't have to cut all the way through.

    Getting someone in to do the job if it can be done in one go would be also a good idea, but make sure they do wet cut as the amount of dust created by dry cut is something to behold. But if you are doing a bit, then a bit more, may as well tackle it yourself at your own pace.

    I looked at Kennards but price was too high for me.

    good luck.

  19. #19
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    I need to cut up an old slab, about 60m worth of cutting. All 100mm deep.

    I looked into some of the options, and settled on buying a quality secondhand machine.

    I figure I can resell it for nearly what I paid since it was bought secondhand. I also have some other concrete cutting work I need to tackle at some point in the future. So I will keep it until thats all done too.

    I got a Stihl TS800. Its a 100cc 5kW 16" demo saw. Its a bit of a beast TBH and I'm a bit apprehensive about using it. Any tips or links I should look at before I kill myself?

  20. #20
    Deactivated User Marc's Avatar
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    It's no different from using a chainsaw.
    Keep the water coming, watch for kickback, use hearing protection helmet gloves and face shield.

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