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Thread: Hollow Concrete Blocks
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15-03-2018, 04:31 PM #1
Hollow Concrete Blocks
Ive been gathering bits of info etc and watched a few videos here n there on DIY pond building...
I started watching a guy who built his pond with hollow concrete blocks which basically is what people choose to do.
This guy laid a concrete pond bottom then when dry proceeded to sit the blocks around the concrete edge and then he must have pushed into the wet mix rebar lengths..
Then he dry laid the hollow blocks onto the concrete base and then he reachex the height he wanted he then filled in the blocks...
Now surely laying the concrete blocks without bedding them onto mortar and mortar ed the edges is asking for issues with regards to water getting into through the block edges etc.....
It had me puzzled why he didnt bed them in.......
You get what you pay for...
https://www.koiforum.uk/water-treatme...y-easypod.html
https://www.koiforum.uk/water-treatme...tom-drain.html
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15-03-2018, 05:13 PM #2
if you think about it when he fills with concrete this will fill all the gaps,my next pond is either an atlantica gardens kit or hollow block,but i till be putting rebar into a row of blocks before base is poured,then when base is in the rebar is already inplace for me to drystack,andi
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15-03-2018, 05:28 PM #3
Actually Andi if you think upon it he is only filling the two hollows...
So basically the block edges are untouched and when you put them side by side if your not using mortar then water will seep through the tiny gap.
Well that is my thoughts..Last edited by Ant62; 15-03-2018 at 06:48 PM.
You get what you pay for...
https://www.koiforum.uk/water-treatme...y-easypod.html
https://www.koiforum.uk/water-treatme...tom-drain.html
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15-03-2018, 06:29 PM #4
My pond was built using hollow blocks completely mortared in with vertical rebars concreted into the hollows. Personally I wouldn’t dream of laying the blocks dry.
Why take the risk, when have you ever seen blocks layed dry in the construction industry.
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Ant62 Thanked / Liked this Post
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15-03-2018, 10:17 PM #5
I layed my blocks dry stacked as followed by Familymans build,no problems at all,when base was layed and dry i cemented the hollow blocks on the bed very level to form the shape i wanted then drilled through one hole of the block into the base for a short rebar to bite into the base then carried on dry stacking which was done in a day.
The hollows were then filled in with more rebar dropped into the hollows and no probs 2yrs later, inside was then rendered i would do the same again if i built another pond.John
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freddyboy Thanked / Liked this Post
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15-03-2018, 10:21 PM #6
You will be fine dry stacking them they won’t go anywhere at all, rebar drilled and chem fixed into the slab and away you go. If your worried about the joint then simply fill them with mortar once done, don’t go to high between filling with concrete though so you can make sure there is no air gaps in the concrete fill and you can simply push the next length of rebar in. Rebar can be in sections so you don’t need to lift the blocks over four or five foot lengths of rebar. Would suggest you purchase the rebar caps just to push on the top which ever way you do it so you don’t stab or poke an eye out!
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16-03-2018, 01:45 AM #7
Just so we don’t encourage a new hobbyist to just dive in and dry stack blocks willy nilly without giving some thought to how it should be done, it’s worth mentioning that if it is done there are a couple of things to take into account.
It’s recommendedthat that if you don’t mortar the joints it’s best to use an architectural adhesive between joints and to backfill with concrete as you go.
All rebar should be in one length if possible but if you have to join it, it should be overlapped by 40 times the diameter of the bar.
This method of construction is recommended for liner ponds or fibreglassed only.
If it’s going to be rendered and painted it would be best to mortar the joints using a waterproofer in the mix.
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16-03-2018, 07:01 AM #8
Correct rog, would like to think if some one is building a pond they have some knowledge of building.
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16-03-2018, 12:11 PM #9
this is how i built mine......
https://www.koiforum.uk/pond-constru...tml?highlight=
David
ah well forget that my pics have gone, basically i laid a thick and reinforced concrete base, reinforced because the bottom drain pipe run is a real weak point in the concrete imo.
If your base is 6 inch thick with a 4 inch pipe running right through it, you have a section where you only have 1 inch concrete above your pipe and one inch below it, which is inadequate imo.
Then i dry stacked 9 inch hollows in a circle 4m across and 2.2 m deep roughly, i had re bar bedded in the base sticking up and then put rebar down every other hole and back filled them all with concrete.
Its very strong, ive been a builder all my working life, so bedding the blocks using mortar would have been no problem, ive done it many times but it offers no benefits really imo for a pond and dry stacking is much,
much faster, i had the shell up in a day.
David
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16-03-2018, 03:58 PM #10
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16-03-2018, 05:56 PM #11
Could you dry stack above ground.... say 4 courses?
What are the implications of fitting a pond window frame when dry stacked?
As a point of note would you not as a matter of course - use a DPM sheet so that would stop water ingress under ground between joints.
Then above ground you would render / paint the outside sealing it?
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16-03-2018, 06:20 PM #12
I did as per Familymans and yes you can dry stack above ground.
Windows, i know nothing about sorry.
I used a Dpm sheet when i laid the base and draped it up the sides as i had a water ingress problem but no problems after and it cured some damp coming through.John
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16-03-2018, 06:57 PM #13
Yes, mine were dry stacked above ground 4 or 5 courses, above or below ground makes no difference.
I rendered inside before fibre glassing, and i rendered outside and painted with normal exterior masonry paint.
this is how i fitted my window.....just neatly cut a rebate into the blocks, for the window to fit into with angle grinder, and neatly finished the corners by hand, then fibre glassed, the window then stuck straight in, on sealant.
from the inside...
Hth
David
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16-03-2018, 07:07 PM #14
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16-03-2018, 09:55 PM #15You get what you pay for...
https://www.koiforum.uk/water-treatme...y-easypod.html
https://www.koiforum.uk/water-treatme...tom-drain.html
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16-03-2018, 10:44 PM #16
when i did my pond, that was the first time id ever done it, and its pretty simple tbh.
I do it fairly regularly now at work, glassing flat roofs on orangerys, infact i built and glassed a storage tank at an industrial unit this week.
The prices some places charge for glassing is ludicrous, i think they just try to make out its some kind of specialised thing only trained people can do, to justify their prices...but its easy.
David
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27-05-2018, 08:47 AM #17
Familyman, What did you use to finish the roof. Is it slate?
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27-05-2018, 09:29 AM #18
It’s a lovely pond David.
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29-05-2018, 12:11 PM #19
i keep toying with the idea of glassing my pond but then worry that I'm going to do something wrong and cause myself extra expense for nothing, any tips I've got a simple rectangle shape with a window, I'm more worried about how to glass the returns, BD's and skimmer so that they don't leak. the kit for my pond is about £500 including VAT or around £900 to get it glassed big difference but at least I have peace of mind if I get someone in.
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29-05-2018, 05:45 PM #20
The Daily pond temp thread
Pond still covered, currently 11.6C Been really mild this year as far as pond temps go. ...