Wall Construction

Starkers · Post by **Starkers** » Wed May 09, 2007 11:19 pm

The base is now laid for my new pond. Happy days. Now I can go upwards rather than down.

I want some advice on blockwork for the walls though. The pond will be 5.5ft deep, 3ft of which will be below ground level. My initial plan was to use 9" hollow blocks and to backfill but before I go ahead and order them I'd welcome peoples views on whether this is the best construction method. Is this method over kill for a 3700 gallon pond?

What would your recommendations be for the wall construction?

Thanks for your help.

Rob Starkey

Gazza · Post by **Gazza** » Thu May 10, 2007 6:17 pm

Hi Rob,

I think the majority of our ponds are well over engineered and as my dad said during my construction "what we building a bloody nuclear bunker"

The thing is we want them to last and not have to worry about it falling down and giving us any grief so i think it piece of mine.Just imagine 3700gls going and you coming home to find the fence missing and your neighbors garden full of water and dead fish

My pond had the the base and then the hollow block tied into the steels of the reinforced base and then we had solid blocks laid on there side as two walls are not seen.Then the front wall was again solid block tied into a brick wall and backfilled in the middle.

Some pictures to hopefully help:

[img]http://www.koipix.com/gallery/albums/userpi ... 2_1289.jpg[/img]

[img]http://www.koipix.com/gallery/albums/userpi ... 2_1296.jpg[/img]

[img]http://www.koipix.com/gallery/albums/userpi ... 2_1300.jpg[/img]

Bob Hart · Post by **Bob Hart** » Thu May 10, 2007 6:54 pm

Mine is 4" blocks, back filled behind them with concrete. I've built a few ponds like this, even knocked one down last year and it was not easy to demolish it at all.

In my opinion, this method is more than strong enough.

Gazza · Post by **Gazza** » Thu May 10, 2007 7:15 pm

Yep i have worked on Bob's pond and knocking bits out and after a couple of broken drills and a big breaker it was done so defiantly strong enough

stoney · Post by **stoney** » Thu May 10, 2007 8:04 pm

Hello all, I built my blockwork from 9" hollow blocks and also put in a reinforcing bar through every other hollow in the blocks to a height of about 500mm. I drilled the base and shoved these into the base at the intervals I wanted. (thought it would be easier to put them in after the base was set rather than trying to get them in the right place with wet concrete)

I then went on to build the total wll with 9" hollows and back filled them, as you say probably over engineered but I definately don't want it to budge, LOL.

Thorny · Post by **Thorny** » Thu May 10, 2007 9:58 pm

Personally I think hollow bolcks are a bit of an over kill, and if not done correctly are doing nothing that a 100mm block laid on its side cant do. To lay hollows correctly You must tie Your steel work for the block work into Your steel work for the floor. Then pour Your slab. Then comes the hard bit. If Your block work is to be 2 meters High. Then thats how high Your stell needs to be sticking up out of Your slab. So in order to lay Your blocks, You need to thread them over the top of the steel pins. Not an easy task if You are only a short lad, as I am. You would then take the blockwork up a 675mm(3 course) and fill the hollows with Concrete, and so on until You reach Your finished hieght.
Personally I would build ponds from 100mm atleast 13 newton concrete blocks, laid flat giving You a 225mm thick wall. . If You want to go that extra mile You could use expamet or bricktor every 450mm in the bed joints. But You must remember to stretch it out before You bed it. Then just back fill in the ground any voinds behind Your blockwork with a lean 3 and 1 mix. It will never go any where.
Justin

Starkers · Post by **Starkers** » Thu May 10, 2007 11:50 pm

Thanks for the replys everyone.

The pond will have semi circular ends (width of pond 2.6m) very similiar to andye's new build posted a few months back. If I go for the hollow block option how easy is it to get the holes in the blocks to line up and does it matter that there will be a large gap at the back of each joint between blocks?

Thinking about it I may be better going for 4" blocks laid flat. At least then I can cut the blocks in half for the circular ends making the blockwork tighter.

Any thoughts.
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JohnC · Post by **JohnC** » Fri May 11, 2007 1:21 pm

To build a radius with a standard length block leaves an awful lot of places -back and front - to fill, so the answer is to cut the blocks in half. With hollows you won`t get enough in a pack to be able do this. I`ve never counted but I would say only 10 to 15 percent of the blocks you buy can be cut in half. So the answer is either cut 100mm blocks in half and lay on their sides or build in brick. Regards JohnC.

stoney · Post by **stoney** » Sat May 12, 2007 9:06 am

I to have a "corner" on my pond, using the hollow blocks created a problem as you can't really mitre then as there is obviously nothing then to apply the motar to....

What I did on the corners was to fill the wide joints on the outer edge with mortar and also I put reinforcing bars in the hollows so that although the rebars are not fixed to the base they do go into the blockwork that is secured to the base and also the blocks that are below groung level.
also filled all the hollows with concrete.

Hopefuly it wont be budging anywhere,,,,,time will tell.

Thorny · Post by **Thorny** » Sat May 12, 2007 9:18 am

If You are building a radius with blocks the only way to do it, is with 100mm blocks cut in half. Tight joints on the inside giving You larger joints at the back. MAKE SURE YOU FILL ALL YOUR JOINTS!!!!!!!!
If You want to know anything a little more teasing PM me I am sure I will be able to help. I pick the odd tip or two up in My job

Justin

Telthepondman · Post by **Telthepondman** » Sat May 12, 2007 2:01 pm

thought i would put my 2 penneth in. i In my humble opinion you cannot beat hollow blocks, but you just cannot generalise and say this will do or that will do. It all depends on your ground structure. Clay being probably the worst scenario. Of couse 99 times out of a hundred 4" blocks will do, even chicken wire render and glass works, but to genaralise and advise without seing the site, or knowing what the ground is like is a dangerous thing.I know, i have seen most problems and have put a lot right over 15 years of building ponds.Hollow blocks laid correctly will not let you down and will be ok in most situations.Now to say you cannot go round bends is a myth. You should have vertical bars in every pot and horizontal bars on every course, interwoven and wired together as you go. On the radius pots bent hoops should be inserted from pot to pot and allso wired in. Horizontal rods should be set into the base before concrete is poured and do not have to be 6 foot high as shorter lengths can be joined on and wired in as you go. The most important thing about laying hollows is the pot filling itself, time and time i see photos where people fill the pots right up to the top and then start laying again.This is just not correct.Lay 2-3 courses at a time, any more than this and things might start to swim a bit.Fill the pots when all is solid enough but NOT to the top only half way up the top block so that when you continue to lay blocks and then pot fill, the fill will bond into the blockwork below.On very tight radiused ponds, small circles for instance use 9" solid brickwork laid all headers, not stretchers as this is a very solid construction.By the way never backfil until the blockwork has gone off solid, as this, and i have seen it could push your walls over.I hope this helps with your decision.OVERKILL, i don't think so. My motto was allways do it once do it right, and it never let me down. Tel.

Hardip · Post by **Hardip** » Sat May 12, 2007 3:17 pm

If building a rectangular pond, do you need to do the rebars all the way to the top?

Telthepondman · Post by **Telthepondman** » Sat May 12, 2007 3:39 pm

The whole idea of the re-inforcing is to make a cage of metal within the blockwork therefore take the bar all the way up. There are different scenarios to this, say if you wanted to convert to facework out of the ground. One detail would be to stop the horizontal bars at groundlevel and continue up with the verticals.You could then use either 4" block or brick internal, and about every 6" or so put a continuous ring of horizontal bar wired into the verts, then you can build your facework in front of the cage using conventional s/steel brickties between skins, also wired into the cage. Does this help. Tel

Hardip · Post by **Hardip** » Sat May 12, 2007 5:58 pm

Yes mate, I think I got the gist of it.

Cheers!

Thorny · Post by **Thorny** » Sat May 12, 2007 8:32 pm

Hi Tel just to clear a couple of things up, How do You use rebar horizontaly on a tight radius. If You can only lay half blocks to get round, how on earth do You manage to get lengths of rebar round, unless You cut it to a maximum 300mm lengths, then it would be join after join and not really do anything. What gauge rebar would You use for this task? As if You are laying this in the bed joints You cant over do it or You will go over brickwork gauge.
As for the 2meter lenghts of vertical rebar, it is a minimum on any building site across the land. Then splined to extensions with tie wire with a minimum of 225mm overlap.
I am pretty jemed up on most specs as I earn my living as a Bricklayer Foreman.
I have built hundreds of 225mm hollow pot walls, You always build them with rebar verticaly but I have yet to build one with rebar in the bed joints. I have used 5mm gauge stainless steel train track, and have even used expamet on the odd occasion as well.

I would just like to know how You go about it, as I have been laying bricks for nearly 20 years and have yet to see it done.
Justin