How to smooth the sharp corners / edges of cinder block [concrete block]

[Mmathis]

I just completed a partial CB wall along one edge of the pond. I also retro-installed a CB collar around the remaining perimeter.

Looking for ideas on ways to "smooth" the sharp, concrete edges so that I won't have to worry about the sharp edges gouging the liner [EPDM] over time. This collar is going to function as my "rock ledge."

1. a mechanical way [like sanding or grinding] the edges smooth -- what tools would I need, as we would probably have to rent or borrow [Home Depot Tool Rental Dept. knows us well, ]
2. I had thought about applying a bead of Great Stuff along the edge -- it would dry into a sort of cushion [I think...]
3. or, gluing an extra strip of underlayment or carpet over all of the edges.....

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Ideas, suggestions, input.......?

 

[Shan]

I taped a thin blue foam on the edges of my bricks before installing the liner. I also used a kitchen placemat in one area.

 

[Mmathis]

I taped a thin blue foam on the edges of my bricks before installing the liner. I also used a kitchen placemat in one area.

What kind of tape did you use and did it stick well?

Oh, and did you have to "prep" the surface at all, other than rubbing or brushing off any debris?

 

[randythawkins]

I had that same situation recently with my waterfall. I took scrap underlayment and placed 3 layers over the top of the block before laying down the "official" large piece of underlayment. that is 4 total and it did a good job of making that sharp corner not sharp when the liner was laid over it. I did have one place where it was not just the edge but the corner of a block and, for that, I lightly chipped at it with a hammer just to knock the point off. then the multiple layers of underlayment went over it just like everything else.

 

[randythawkins]

...I hit "Send" too soon...

I did not glue mine, just laid them there. Things can move around while laying the things on top of it but, once everything is in place and water pressure and rocks are holding it still, it won't go anywhere.

 

[Big Lou]

Double underpayment over the blocks followed by a layer of semi-dense foam sheet (like sold at a craft stores or for a bed from Walmart) or even layers of cheap blankets or rugs. Top the padding with underlayment. Spray on expanding foam can become brittle and break off.

Another tip. Place a section of additional liner that has been cut to the width of the wall. Of course, this is not water proof but provides very pliable pad between the stone and the true liner.

 

[randythawkins]

Another tip. Place a section of additional liner that has been cut to the width of the wall. Of course, this is not water proof but provides very pliable pad between the stone and the true liner.

Before placing rocks in my waterfall I added 1 to 2 layers of scrap liner under them. I did not want a heavy rock pressing on my primary liner. I figured some layers on top would help pad any roughness of the rock.

 

[RobAmy]

A small grinding wheel with work real easy. Something in the 4 1/2" range will be fine. They have different grinding wheels so tell who ever what you want to do so you get the correct one, just make sure it is thinker, the real thin wheels are more for cutting masonry. It will be dusty but you can use a hose to help reduce the dust but this will create another problem with a bit more mess. if you do not have much just use a dusk mask and deal with the dust and then you can use a air hose to clean up the dust or a shop vac.

 

[minnowman]

You could get a rub block from anywhere that sells concrete supplies. It looks like a flat rock with a plastic handle.

 

[Shan]

What kind of tape did you use and did it stick well?

Oh, and did you have to "prep" the surface at all, other than rubbing or brushing off any debris?

I just dusted off any dirt and then used Duct tape. I layed the pond liner over and then a brick on the top, so that's probably what keeps the foam on--I'm not sure how the tape would hold without the brick on top.

 

[Mmathis]

@RobAmy
@minnowman

I'm on my way to Home Depot soon. My HD app shows that they do have some "rub blocks" in stock [had never heard of those] and are inexpensive. Also going to see if they have rental grinders in case the block doesn't work [or requires more elbow grease than I can spare -- not as young as I used to be, LOL].

@Shan Even if the above mentioned do work, I'll probably still go with something a little extra to cover the edges. I wondered how duct tape [or any adhesive] would work, putting it over dusty, dirty bricks [I say that, 'cause even brushed off, they're still going to be coated to some extent]. But it really only has to grip long enough for you to get the underlayment & liner positioned, then those + the water would hold the foam in place, I would think.....

Thanks to everyone who has replied! I thought I was the only one to have this issue, so it gives me hope to know that there are others out there doing the same [similar] thing.

 

[Mmathis]

I ended up buying an angle grinder today -- it was going to cost about the same amt. to rent one. Tried it out on the cinder block edges and it did a wonderful job, though I'm not finished yet.

This is the blade I got

 

[Big Lou]

You go Turtle Mommy!