Finishing a square liner in a round above ground pond

Discussion in 'Pond Construction & Equipment' started by icerabbit, Oct 4, 2012.

  1. icerabbit

    icerabbit

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    I am working on my first pond / water feature with a liner. (previous experience full masonry & pre-formed)

    Originally we were going to do some kind of stacked / locking stone and I figured the liner could just sit underneath the top row, but we didn't like the look of those stones so much for a larger feature. So went the bricks & mortar route, but now I'm having some trouble with the final details at the top.

    It is 12 ft in diameter, about 3ft at its deepest in the center of the "bowl". Dug into the soil about one and a half foot and then tapers up about a one and half foot masonry wall. It has a layer of sand and two layers of tarp as a protectant against the brick work. Couldn't get official cloth inexpensively asap when I realized I needed it and the liner & water HAD to go in ;)

    We're nowhere near summer, so the 20x20 liner did not smooth out as much as I thought it would, and I've got plenty of little lines, wrinkles, ridges and then of course some trickier bits and bigger folds going up the sidewall over the edge. I currently have the liner draping over the edge and trimmed off the biggest excess so that it is about touching the ground. Plenty long.


    Should I cut the liner flush with the outer edge of the brick work? Shorter?
    Or leave it longer and see about folding some back under, by making some cuts and folding flaps in?

    Then should I trim it back an inch or so from the edge and just embed it in the mortar, and put the cap stones?
    I still need to find the natural stone to serve as caps, and may finish the edge in the spring if it stays wet out given the other fall chores around the house.

    How worried should one be about wrinkles and fold lines in the liner?
    I plan to empty it before winter as it would freeze solid and likely damage the masonry wall. So I do have the option to fidget with the liner some more next year. Though starting it up in the spring, it will likely be similarly cool out.

    I would grab a fresh picture, but it is raining out.

    Thank you :)
     
    icerabbit, Oct 4, 2012
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  2. icerabbit

    Waterbug

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    I'm assuming this is EPDM liner...

    I know it's very difficult to work with all that extra liner but it can be very risky to cut. You'll think...well this is clearly way outside of the pond...and later...what the? How you fold greatly affects the amount used. If you do need to cut I would certainly cut as little as possible. I hate to cut a liner before the pond is full.

    The most important thing is to make sure the edge of the liner is always above the waterline. This may sound like "well duh" but I can tell you it is very easy with lot's of folds to hide a dip. So before I cut or nail I place the edge of the liner between two fingers and follow that edge completely around the entire perimeter to check. Cut a liner with a dipped fold and you are hosed.

    Good to have one person in at the bottom and one standing outside (the skilled position) trying to wrestle the flopping liner.

    Frankly though, in a round, not huge pond, I kind of think it's an almost impossible task. Even a perfect pleat job still looks like a ton of wrinkles and folds imo. For me it's just easier to fold a little and then mortar over the liner. Lots of people don't like that for many reasons including fear of freeze damage. But that's what I would do. It's a personal taste issue whether bare liner looks OK or if the extra work and expense is worth the result.

    For the cap what I like best is embedding pressure treated 2x2 wood into the top course. Then I can nail the liner to the wood with roofing nails. Just easier for me that way. I have seen people shoot anchors thru the liner and into the concrete...not something I would for fear of the concrete cracking. Plus I've never not had to pull a few nails and reposition.

    The liner does have to be secured some way at top. An inch of liner isn't going to want to make that 90 degree turn, not with all the folds. Also, with the bunched up liner you could have 1/2 to 1" of liner under the cap on one side so the cap isn't going to want lay flat without a lot of mortar on the other side. I've never done this, but you could put a big dollop of mortar on the outside edge and some under the cap stone also on the outside edge, and then holding the cap vertical inside the pond, press the cap against the liner and use it to roll over the liner. Then push some mortar in between the liner and cap on the inside edge. Just a guess.

    I know virtually everyone thinks concrete and freezing means busted concrete but that's not completely true. You may want to research the risk more if draining, and keeping it drained is a pain. Keep in mind that a drained pond also has risks. Like a tree branch falling in on poking a hole in the liner. Or a cat, raccoon, dog, whatever getting into the pond and clawing a hole thru the liner.

    Sounds like you've posted some pictures some place...I'll look around...sounds like an interesting pond.
     
    Waterbug, Oct 5, 2012
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  3. icerabbit

    icerabbit

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    My apologies for checking back into this thread a bit late.

    Thank you for the advice, Waterbug.

    When the liner was placed in the pond, I started filling right away after initial positioning, to try to keep things as smooth and best positioned as possible, making small adjustments while it was filling. The 12ft diameter circle is masonry, so I can't nail anything down to the edge. I currently have it trimmed folding down over the exterior face back to the ground and weighed down. As it is cooling down rapidly outside and we've had some frosty nights, I don't think I can fidget with the liner inside the pond.

    (photobucket is not liking my password tonight or I'd add a few photos)

    We did finally find stones in a color, size & shape we liked to serve as cap stones and picked them up. It will take a fair amount of cutting to get them to a trapezoid shape, to conform to the circle, but look neat. I also picked up a first trailer load of river stones.

    I think my next step will be to trim the liner & underlayment flush with the outer edge of the masonry (not inside edge). Then time & weather permitting I'll place a mortar line on top of the liner and set the cap stones down.

    With our winters, the pond would freeze completely solid for several months. As thick and solid as the wall is built, there may not be any freeze damage, but I'd rather not take the chance. If we were more south with just a few inches of ice, I would go for it. It is little trouble to have the pump drain it down while I'm doing other gardening stuff. Same for filling it in the spring.

    Originally I was going to have the entire thing more as a bowl shape, against freeze damage, but I was going to lose too much water volume and had to add too much soil back.

    Now let me see if I can fix this photo-bug-bucket thing.
     
    icerabbit, Oct 17, 2012
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  4. icerabbit

    icerabbit

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    icerabbit, Oct 17, 2012
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  5. icerabbit

    Waterbug

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    That could be a bit of a problem because mortar doesn't stick to liner and the thin mortar joints wouldn't be very strong. Mortar really depends on sticking to a strong base structure. You can lay a wire or fiberglass mesh in the mortar bed and have a thick bed, like 1", to try and create monolithic ring. I think that is your best bet.

    The only other thing I can think of is to glue the liner to the wall and then glue the cap stones to the liner. Not a great choice imo, more expensive, messy and could be difficult to remove down the road.

    Pond looks nice.
     
    Waterbug, Oct 17, 2012
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  6. icerabbit

    icerabbit

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    Thanks for the compliment.

    I had wondered how well the mortar might stick to that liner - which is EPDM 45 by the way. Just like you , I'd rather not use any glues to adhere the liner down to the masonry nor glue the cap stones down to it.

    I'm wondering if I could try the following, trim the liner to half width of the top layer of stones then just embed that half width flap in the mortar bed. That way there could be a continuous mortar ring on the outer half of the wall, that can stick down to the stone wall and the cap stones. Maybe use the extra strength mortar with additional adhesive.
     
    icerabbit, Oct 17, 2012
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  7. icerabbit

    Waterbug

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    Yes, the half way thing would be a normal method. What concerns me, and now that I see a picture I'm much less concerned, keeping the liner laying down while you try to do this. Right now the over hanging liner is pulling it down, When cut I think it'll want to pop up at the folds...it's the folds that cause the trouble and you have a lot but less than I first imagined. It can probably be done but pretty tricky.

    I've been in the same boat you are when I first started building ponds. I was in such a hurry I skipped thinking about the cap and that always caused great pain. Maybe you could still design a better solution? For example you seem to have lots of liner...can you add another course? If you could you can embed a strip of wood which the liner can be nailed or screwed to. That's what I normally did. Or I'd finish with a bond beam block (hollow trench inside) and the liner can be pushed into the void, filled with concrete and you're ready for the cap.

    Or in stead of another course you could cut some HardiBacker board to the shape of your wall. Lay mortar over the liner and lay the board nice and level just as you were going to do with the cap rock. After the mortar sets you can drill thru the board, mortar, liner and iinto the wall. Then screw it all down (not too tight). It wouldn't take a lot of screws, maybe one every 16" or so, staggered between front and back edges. Then you can trim the liner and mortar the cap rock to the Hardi. A bunch of steps but it it would be easier to get a nice looking outcome, less stressful maybe.
     
    Waterbug, Oct 17, 2012
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  8. icerabbit

    Craig58

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    Similar style to my ponds. Have you looked at the one I have under construction?

    In pic 1, you can see where the liner comes up over the lip. On the small shelf we used garden edger. The flagstone was than glued and mortared onto the block and edger.

    This is after 17 yrs. The garden edger eventually broke down. We were going to replace them but decided to build a new pond.

    You only want to trim and finish when the pond is full. The liner was a pain for us mostly in the corners. No real easy solution except to work them, walk away, work them again, walk away, etc.. until you like it. Then cut the liner and install the capstones ASAP before you have time to rethink yourself!!! :razz: On a round pond I would suggest trying to plan a take up fold on a regular basis around the pond so that all the folds look about equal and are equally spaced. Easier said then done.

    Craig
     

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    Craig58, Oct 17, 2012
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  9. icerabbit

    icerabbit

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    Thank you, waterbug.

    You gave me a few extra options to consider.

    Going up a row is an option. I have the stone to do it. However from an visual / aesthetic point of view we decided against that. The original idea was to have it higher and be a sitting height, have a little path, maybe small bench. But, we found it very functional at three and just want to put plants around it, without a path & bench. I did dry-stack a fourth layer and we thought it was sticking up too high, changed the viewing angles to the water (can't see into it as well) and would be harder / take longer to conceal with young plants.

    Cutting a groove into the center of the upper row of block certainly can be done (probably after I drain it down and fold the liner in) to stuff the liner edge in, and maybe just put a bead of adhesive there to keep it in place while I'm working on the rest. Though I could probably accomplish that without the groove.

    I'm not sure about going the wood route, that'd be a lot of work considering I'm dealing with a circle. It's not just a straight cut to put a strapping strip in. The wood would also have to go around.

    To keep the liner in place I had already planned to work my way around the circle, by trimming the liner back a number of feet and doing the necessary work, while the rest is either held down by blocks.

    I'll have to think about it some more. I'm in no rush to get the cap stones secured down. I rather trim the liner up and cut the stones, and let it all sit loose for a few more weeks at which point it will get, covered in snow, than to shoot myself in the foot.
     
    icerabbit, Oct 17, 2012
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  10. icerabbit

    icerabbit

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    Thank you Craig.

    I haven't looked at your new pond construction photos.

    Thanks for those two images. That lip certainly seems useful. 17 yrs is a good shelf life. I'd be happy with that.

    So, your liner is basically cut flush with the upper vertical edge of your masonry wall, right?

    I think I need to stay on the horizontal with my liner edge. I don't want water to get behind the liner. Or have it fall away from the vertical wall. I could cut such a shelf into the blocks, but as I'm working in a circle with pretty thick liner, I think I would only be complicating things needlessly with more folds, by adding that 90deg angle. I'm also not sure what material I'd stuff into that space to hold the liner in.

    What is the garden edger? Some kind of lumber piece? Rubber? Or stone?

    I agree with you on trying to space the folds out in the liner and making it as flush and even as possible. I kind of tried to do that as I started to fill it, but to a large extent the liner decided things for us. LOL. I don't envy you your 90 degree corners, though at the same time mine is like a continuous corner. Haha.
     
    icerabbit, Oct 17, 2012
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  11. icerabbit

    Craig58

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    The garden edger we used was made out of cinder block style stone. We expected it to break down over the years. We were actually happy it lasted as long as it did. I was expecting a max of ten when I first built it. They are typically used to as border edgers for gardens and walkways. They are usually made of brick, with the scallopped edge being the most common. But they can come in different varieties.

    Yes, our's is cut flush at the top. No water should normally get behind the liner unless you overtop the pond. So you want an overflow pipe.
    That's also why I suggest you really fill it up and let it really pull the liner down and stretch it out before doing any trimming. Let it sit for a few weeks. Because you'll want to keep the water level close to the top, your margin for error is small. Should you cut the liner and than it slips done 1/4" or a 1/2" your pond level has jsut dropped and your overflow pipe will be obsolete. The water will exit the liner at the low point and never reach your overflow pipe.

    The garden edger is what holds the liner up against the back portion of the wall. The flagstone top is glued to both the garden edger and block wall so that helps prevent the garden edgers from slipping forward and allowing the liner to slip. Also of course the water will push against it and hold it up too.

    Are you planning on cutting the flagstone tops at angles so that they are flush against each other? I would suggest doing them as flush as possible and then using a retaining wall glue to glue the ends to each other. Mortar mixes never really held up in my 1/4-3/8" joints. They cracked and broke up after a few years and every few years I'd have to repoint the joints. A losing battle.

    As far as folding I'd try to keep them to 4-6" folds every 3-4 ft if possible. Adding the ninety degree bend doesn't really complicate the folds. You just have to allow the fold to contnue in the driection it is going. I.e. don't try to make it go up straight once it comes up over the lip. Let the fold continue across at the same angle as it comes off the circular wall. This is why you don't want to trim anything unitl the very, very end.

    Craig
     
    Craig58, Oct 17, 2012
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  12. icerabbit

    Craig58

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    Here's another picture of our pond to give you a better idea of the edging block.

    As you can see there is a hollow spot to the left of the bust. That edger broke down. The edger to the right is breaking down and has slipped forward a bit.

    In the second pic are edgers that still haven't broken down and still look like they did when we installed them. Right now about 30-40% of our edgers are in some form of break down or are gone entirely.

    Since you have a more traditional brick wall, you could use standard red brick in your pond as edging adn it would look good with the style pond you used. It should hold up much better than the edgers we used. We used a natural stone to do our pond walls on the outside so we didn't think a red brick edging would blend in as well.

    You can probably use the same brick you used on the outside and cut them to the right size.

    Craig
     

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    Craig58, Oct 17, 2012
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