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How can I remove concrete from concrete?

BradN
Retired Team Member
Retired Team Member

How can I remove concrete from concrete?

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Hi guys. This is the current sorry state of our narrow side yard. We've removed the old paling fence and our old raised garden beds and are going to drop in new metal garden beds like the one my partner and project boss has assembled in the pic above.


The problem is that the new beds aren't going to sit level because of the concrete that dripped down along the fenceline when our neighbour built the retaining wall and core-filled the Besser-block fence pillars.   

 

What would be the easiest way of removing some of that concrete from the bottom of the retaining wall so the raised beds can sit flat? It won't crack off easily just by hitting it with a pick. Would an angle grinder be suitable? Terrible pic below of the concrete or mortar at the base of the retaining wall:

 

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Also, would it be a good idea to paint the retaining wall and fence pillars? If so, what sort of paint would we need?

 

When it rains some water seeps or dribbles through the retaining wall in places where it can find gaps in the mortar, and we found a fair bit of green algae growing around those spots when we recently took down the old paling fence. It's not a big problem to clean that off, but the whole bare wall looks pretty ugly... 

 

One last question: It seems that corrosion has narrowed the holes in this 50mm metal tubing so that I can't fit 3mm clothesline through it any more. Could I slightly widen the holes with an 18V drill? What sort of bit would I need? I don't know what kind of metal it is.

 

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Anyway, thanks in advance for all your sage advice. Here's a bonus pic of our silly old dog Night catching some sun by the old timber retaining wall. He's a Very Good Boy.

 

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Cheers,

Brad

EricL
Bunnings Team Member
Bunnings Team Member

Re: How to remove concrete from concrete

Hi @BradN

 

Let's start with your concrete retaining wall, I suggest using a Spear & Jackson 115mm Brick Bolster and a hammer. In this manner, you'll have better control and you can precisely hit the cement overflow and not the retaining wall. You can also use it as a scrapper to remove the cement splash that's gone on the face of the Besser block. It will be slow going, but you'll see that once you hit the weak spot of the cement overflow they easily come off.

 

If the gaps in the Besser blocks are big enough to be plugged in, I recommend using Gripset Betta 1kg Water Plug, It absolutely stops water leaks, I suggest using a trowel to get a nice finish. To paint the wall I propose using any exterior paint from the three major brands in a low sheen. These paints are formulated to work on almost any surface and are self-priming.

 

But if you want something tough, you can use White Knight 4L Medium Grey Ultra Pave Heavy Duty Concrete And Paving Paint. This paint is made to be driven over so it is a bit overkill for the retaining wall. It can be tinted to your preferred colour so please look carefully before choosing a can.

 

If you have a few drill bits in your toolbox, I suggest testing a few and seeing which one fits into the hole of the metal tubing. When you find one that fits, look in your toolkit for the next size up. Most modern drill bits are now rated for multi-use so you can use them on wood and on steel. However, if you want a steel-rated bit just bring the drill bit you've tested and match it to one at the store. Please make sure that it's bigger than your clothesline. Once you've drilled a bigger hole spray or paint over it with any leftover paint you have to protect the exposed steel.   

 

My last tip, make sure to leave a gap of at least 30mm between the garden bed and the retaining wall to prevent moisture from getting trapped in between. It will make the steel garden bed last longer.

 

Tell Night for me that he is a good dog and please offer him a biscuit.

 

Let me know if you need anything else my friend, I am at your service.

 

Eric

 

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BradN
Retired Team Member
Retired Team Member

Re: How to remove concrete from concrete

Hi @EricL . Thanks so much for that fantastic, comprehensive advice! I shall begin by investing in that brick bolster first thing Saturday morning.

 

In the meantime I'll give Nighty a biscuit and let him know it's from you.

 

Cheers and thanks again,

Brad

BradN
Retired Team Member
Retired Team Member

Re: How to remove concrete from concrete

Hi folks and @EricL . A bit of an update on this one, and another question. 

 

On closer inspection, what I thought was concrete oversplash down the bottom of the fence was actually the solid concrete footings of the fence. I was never going to chip that away with a brick bolster so that the garden beds could sit level!

 

Instead I screwed together a couple of big U-shapes out of 10cm treated Pine and pushed them up against the concrete footings and then plonked the garden beds on top. It worked pretty much perfectly. My partner, Sally, has planted them out with lettuce, tomatoes, cucumbers and peppers, with some marigolds and nasturtiums as companions. At some point soon we'll rig up something simple for the climbers to climb on. 

 

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Re: the clothesline. I drilled out one hole slightly larger and then realised that all the holes had suddenly become big enough to put the 3mm clothesline through again, like I'd done before. My best guess now is that the metal must slightly expand and shrink with changes in temperature, sometimes making the holes just slightly too small to get the clothesline through. Does that sound plausible to you? In any case, I've got the clothesline fixed, so yay!

 

Now Sally has picked up these bamboo panels, which we want to mount on the Besser block fence out the back. What do you think is the best way of going about this? Will we need to screw a horizontal timber batten to the Besser blocks and then screw the panels to the batten? I've never drilled into bricks before, but Sally has a rotary hammer drill from when she put up some floating shelves a while back – she's the real handyperson around here...

 

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Anyway, it would be great to know what you think we should do here.

 

Cheers and thanks,

Brad

EricL
Bunnings Team Member
Bunnings Team Member

Re: How to remove concrete from concrete

Hi @BradN

 

Sorry to hear that the bolster did not work, but I'm glad to hear you found a way around it. In order to take advantage of all that wall space, I suggest slowly investing in a vertical garden setup. Going vertical is a bit of a challenge, but when you have it all set up you have this massive wall of green and it all depends on what you're planting. Part of it can be veggies, part of it can be ornamental there is no limit to what you can plant. So instead of seeing an ugly fence, you see this beautiful layout of plants that is relaxing to see.

 

Eric

 

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BradN
Retired Team Member
Retired Team Member

Re: How to remove concrete from concrete

Hi @EricL . The bolster worked great! It chisels away concrete, no problem. My mistake was thinking that I was only dealing with a little bit of oversplash, when I was actually looking at the whole big, solid concrete footings of the fence. But I got around that by making the Pine bases for the garden beds. I'm now trying the bolster as a chisel to break pallets for other projects (don't get too excited about those; they're pretty basic).

 

I'm very interested in vertical gardening (I've had a bit of success growing cherry tomatoes in hanging baskets before). It's something I'll definitely look into once we've got these bamboo panels up.

 

I'm guessing that for the bamboo panels we need to screw or bolt a timber batten on to the Besser-block fence. What kind of drill and screws or bolts would we need for that?

 

Cheers,

Brad

 

 

EricL
Bunnings Team Member
Bunnings Team Member

Re: How to remove concrete from concrete

Hi @BradN

 

It all depends on where you are mounting onto. If you are mounting it onto the Colorbond posts, it will be necessary to put battens on. However, if you are mounting it to the masonry wall plugs and screws should suffice. I suggest having a quick look at this discussion - Bamboo fence panel for extra privacy by @Shannon

 

For the Colorbond posts, I suggest using  70 x 22mm 4.8m Decking ACQ Treated Pine cut to length and screwed into the vertical Colourbond posts with Buildex 8 18 x 30mm Climacoat Countersunk Ribbed Head Metal Tek Screws 50 pack. If you are mounting to the masonry I recommend using wall plugs in conjunction with Zenith 8 - 10 x 40mm Galvanised Countersunk Rib Head Timber Screws - 100 Pack.

 

If you need further assistance, please let me know.

 

Eric

 

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BradN
Retired Team Member
Retired Team Member

Re: How to remove concrete from concrete

Great! Thanks, Eric. I'll show all this to the boss, and I expect we'll have a crack at it on the weekend.

 

Cheers,

Brad

BradN
Retired Team Member
Retired Team Member

Re: How to remove concrete from concrete

Hi @EricL . Well, we got those bamboo panels up, and I think they look pretty decent. We put up four battens of the decking Pine using Ramset EasyDrive 8mm 75mm Hammer-In Anchors. Then we screwed through the timber crosspieces of the bamboo panels into the battens.

 

You can only see the top row of battens in this pic; we put another layer further down so we could fix the panels to them through the lower crosspieces as well. We've had some pretty high winds here over the past couple of days and they've stayed up, so that's a good sign.

 

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Our ancient water feature is in an advanced state of decay, but I'll clean it up and it'll go all right until we get a chance to replace it.

 

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Thanks again for your invaluable advice. I don't know what we'd do without you!

 

Cheers,

Brad

EricL
Bunnings Team Member
Bunnings Team Member

Re: How to remove concrete from concrete

That's awesome work @BradN, thanks for the update. Covering up that fence has already transformed the look of that area. Will you be doing the rest of the fenced area or just a small part of it? 

 

If you need help with anything else, please let me know.

 

Eric

 

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