Breaking out monolithic concrete
Discussion
Hi all. Another massive concrete job for myself, got to break out our garage floor to 8 inches deep ish. Problem is the garage subsided many years ago and the floor (luckily not the whole building) moved by about 6-7 inches on one side. Somehow it hasn’t cracked and from test holes and chatting with our builder, it looks like the slope they built on, they just filled the void with concrete, so one side of the garage is about 8-10 inches deep and the other side about 8ft deep. Poured 70 odd years ago it’s incredibly hard. Tried our electric breaker and didn't really touch it, hired a belle bulldog hydraulic breaker and I think the chisel came off worse than the concrete and didn’t really make much progress. Only thing left to do is hire a mini digger and pecker but the biggest I can get through the doors is a 1 tonner but I’m afraid I’ll find the same thing. Have looked at raising the whole floor but it would mean side door, main doors, gable, bits of plumbing/electrics and head room would all become an issue given the massive difference in levels. Would appreciate any brainy ideas at this point!
Had a very similar job to do with a garage floor laid in the 60’s. Long story short the only thing that made any impression was a 3.5 tonne digger with a pecker; the arm had to be mostly horizontal rather than the optimal vertical because of the height.
It took a week and was excruciatingly noisy. We had to run the operators in shifts.
And then of course, you are left with a pile of rubble, you pay to take it all out and away, dug out a foot, and then pay to bring it all back in as crushed concrete…
It took a week and was excruciatingly noisy. We had to run the operators in shifts.
And then of course, you are left with a pile of rubble, you pay to take it all out and away, dug out a foot, and then pay to bring it all back in as crushed concrete…
Try cutting it first? That way you will have blocks that want to break out rather than chipping away at it and hoping it fractures on its own.
Also form a hole or edge and work away from that. Could start it off by cutting deep but narrow sections and snapping them off with a breaker/bolster/crowbar.
Does depend on what if any reinforcement is in it and what size/quantity of aggregate.
Drilling can also help encourage it to break, doesn't have to be stitch drilling. Nice big SDS bit can make useful sized holes and help confirm the depth too.
Been there & done that, hardest bit was where I found someone had used 1" solid bar for reinforcement which took some cutting.
Also form a hole or edge and work away from that. Could start it off by cutting deep but narrow sections and snapping them off with a breaker/bolster/crowbar.
Does depend on what if any reinforcement is in it and what size/quantity of aggregate.
Drilling can also help encourage it to break, doesn't have to be stitch drilling. Nice big SDS bit can make useful sized holes and help confirm the depth too.
Been there & done that, hardest bit was where I found someone had used 1" solid bar for reinforcement which took some cutting.
PhilboSE said:
Had a very similar job to do with a garage floor laid in the 60 s. Long story short the only thing that made any impression was a 3.5 tonne digger with a pecker; the arm had to be mostly horizontal rather than the optimal vertical because of the height.
It took a week and was excruciatingly noisy. We had to run the operators in shifts.
And then of course, you are left with a pile of rubble, you pay to take it all out and away, dug out a foot, and then pay to bring it all back in as crushed concrete
Good grief that sounds horrendous, and similar to what im finding. Luckily if we do ever manage to get the top layer of it off, we should only need to bring in a bit of type 1 as the levels will be pretty much there. Thanks for the motivation that you did manage to do it though!It took a week and was excruciatingly noisy. We had to run the operators in shifts.
And then of course, you are left with a pile of rubble, you pay to take it all out and away, dug out a foot, and then pay to bring it all back in as crushed concrete
JoshSm said:
Try cutting it first? That way you will have blocks that want to break out rather than chipping away at it and hoping it fractures on its own.
Also form a hole or edge and work away from that. Could start it off by cutting deep but narrow sections and snapping them off with a breaker/bolster/crowbar.
Does depend on what if any reinforcement is in it and what size/quantity of aggregate.
Drilling can also help encourage it to break, doesn't have to be stitch drilling. Nice big SDS bit can make useful sized holes and help confirm the depth too.
Been there & done that, hardest bit was where I found someone had used 1" solid bar for reinforcement which took some cutting.
Yep, tried cutting it with a stihl saw and it was definitely more successful but INCREDIBLY slow cutting even with a really nice diamond blade. It looks like it’s made up of a lot of small flint, sharp sand and a boat load of cement given the colour. I put a 1 1/2 foot bit through it and was still going😂. Luckily they decided 10ft of concrete doesn’t need reinforcement so in my test holes I didn’t come across any.Also form a hole or edge and work away from that. Could start it off by cutting deep but narrow sections and snapping them off with a breaker/bolster/crowbar.
Does depend on what if any reinforcement is in it and what size/quantity of aggregate.
Drilling can also help encourage it to break, doesn't have to be stitch drilling. Nice big SDS bit can make useful sized holes and help confirm the depth too.
Been there & done that, hardest bit was where I found someone had used 1" solid bar for reinforcement which took some cutting.
reggie747 said:
As said, put a Stihl saw depth grid pattern of cuts over it.
Once you have the first "cube" out, the rest will follow.
And yeah, it will be dirty sweaty one too.
Agreed, starting to think this is the only way. Do you have any advice for spacing? Can't be too liberal with it as those diamond blades ain't cheap!Once you have the first "cube" out, the rest will follow.
And yeah, it will be dirty sweaty one too.
Chris240 said:
Agreed, starting to think this is the only way. Do you have any advice for spacing? Can't be too liberal with it as those diamond blades ain't cheap!
I'd go with at least with a 300mm grid.Yeah, I get that blade price is a consideration so look around for a bundle deal (and make sure you get concrete quality ones, they're not all the same)
Chris240 said:
Mammasaid said:
Could you hire in a floor saw? Would put in deeper cut and be less backbreaking.
Did have a look but it would have to be done in layers as can't go deep enough in a single cut, and very hard to then wheel over the rough surface for the second cut. 
https://www.husqvarnaconstruction.com/uk/floor-saw...
It doesn't necessarily have to be a full grid of cuts; cut in rows in one direction, cut one or two slots in the other to get it a starting point to remove a section, and that might be enough to encourage it to come out.
A full grid will give sections that will want to snap off more cleanly across the base but even just rows will give it a starting point to break.
Main point is that solid concrete is hard to chip away if you're just stuck trying to pulverise or crush it but if it has some space to move into it really does like to fracture.
For a slab inside a garage get the middle out and the rest will want to follow.
A full grid will give sections that will want to snap off more cleanly across the base but even just rows will give it a starting point to break.
Main point is that solid concrete is hard to chip away if you're just stuck trying to pulverise or crush it but if it has some space to move into it really does like to fracture.
For a slab inside a garage get the middle out and the rest will want to follow.
Your description has a bit a Fred Flintstone feel to it...
You could use expanding grout to break the concrete, something like this:
https://dynacem.com/uk-en
My inner child would like to think that explosives are the best idea, especially if things are required to go according to plan.
You could use expanding grout to break the concrete, something like this:
https://dynacem.com/uk-en
My inner child would like to think that explosives are the best idea, especially if things are required to go according to plan.
Chris240 said:
Hi all. Another massive concrete job for myself, got to break out our garage floor to 8 inches deep ish. Problem is the garage subsided many years ago and the floor (luckily not the whole building) moved by about 6-7 inches on one side. Somehow it hasn t cracked and from test holes and chatting with our builder, it looks like the slope they built on, they just filled the void with concrete, so one side of the garage is about 8-10 inches deep and the other side about 8ft deep. Poured 70 odd years ago it s incredibly hard. Tried our electric breaker and didn't really touch it, hired a belle bulldog hydraulic breaker and I think the chisel came off worse than the concrete and didn t really make much progress. Only thing left to do is hire a mini digger and pecker but the biggest I can get through the doors is a 1 tonner but I m afraid I ll find the same thing. Have looked at raising the whole floor but it would mean side door, main doors, gable, bits of plumbing/electrics and head room would all become an issue given the massive difference in levels. Would appreciate any brainy ideas at this point!
Am I reading that right, the concrete tapers from 8’’ - 10’’ to 8ft (!) thick?JoshSm said:
It doesn't necessarily have to be a full grid of cuts; cut in rows in one direction, cut one or two slots in the other to get it a starting point to remove a section, and that might be enough to encourage it to come out.
A full grid will give sections that will want to snap off more cleanly across the base but even just rows will give it a starting point to break.
Main point is that solid concrete is hard to chip away if you're just stuck trying to pulverise or crush it but if it has some space to move into it really does like to fracture.
For a slab inside a garage get the middle out and the rest will want to follow.
Yeah this is what I’ve had most success with so far and as you say just trying to pulverise it is not going anywhere in my lifetime😂A full grid will give sections that will want to snap off more cleanly across the base but even just rows will give it a starting point to break.
Main point is that solid concrete is hard to chip away if you're just stuck trying to pulverise or crush it but if it has some space to move into it really does like to fracture.
For a slab inside a garage get the middle out and the rest will want to follow.
Freddie Fitch said:
What are you going to do when you've dug it out?
Can't you leave it there and build on it?
Sadly not as it would require rebuilding of the gable, garage doors, side door etc if the levels are changed. Far too much for self levelling screed and not much by way of other options!! It’ll just be re-poured flat to match up with the garage.Can't you leave it there and build on it?
Custerdome said:
Your description has a bit a Fred Flintstone feel to it...
You could use expanding grout to break the concrete, something like this:
https://dynacem.com/uk-en
My inner child would like to think that explosives are the best idea, especially if things are required to go according to plan.
Haha the thought had occurred to me. I did look at that stuff but fear quickly took over my excitement that it could end up pushing the garage walls sideways given the pressures you’re talking about here lolYou could use expanding grout to break the concrete, something like this:
https://dynacem.com/uk-en
My inner child would like to think that explosives are the best idea, especially if things are required to go according to plan.
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