Concrete blocks

[chrisd1]

Hi all. I am after some advice, I currently have a 12ft x 13ft x 3ft pond which I want to raise by 2ft, I have a rienforced concrete ring 1ft x 1ft, what I want to know is are 9in x 18in x 4in blocks layed on there edge strong enough to take the pressure of the water or would I be better to lay them down flat ?
thanks
chris

[Jules]

Chris 2 ways of doing it and I am sure Justin will back me up. You can lay them on their sides and create a wall like that or stand them up allow a 1 inch gap and have another external course the backfill the gap as you go. Both ways are secure and both ways will probably take a similar amount of time to lay/costs once you include labour and materials.

Jules

[rappy]

Hi Chris,im a bricklayer and i would recommended laying the blocks on there sides as it makes it one solid wall.You can lay them as normal on the 4 inch side,but you would have to tie the 2 skins of block work together with butterfly ties.Butterfly ties arent cheap any more as they are stainless steel.Also when filling the gap between the 2 skins of block work(cavity) with concrete you have to do it in stages as the weight of concrete will blow the 2 walls apart if atempted in one go.You will then have to account for cost in concrete,which in my area i can get for £95 m2.

If cost isnt to much of an issue,this is the way i would go and would work out about the same price as 2 skins of 4" block with cavity filled with concrete.I would go for 9" hollow concrete blocks and rod them with reinforcing steel and then concrete.With these blocks you can concrete in one go.This would be the strongest way.Would be best if you good put a few starter bars in the slab so you can tie the reinforcing rods too,which then it would never move

[Thorny]

I hope I have got this right in My head, You are planning to raise Your pond out of the ground by two foot. So the answer is what do You want it to look like. Do You want the blocks exposed, ugly as hell. So You could render them. Personally I would all day long build two 100mm skins with a cavity that will be back filled with a slurry concrete mix. The wetter the better as this will fill every knock and cranny. In order to only come out of the ground by two foot You would need two course of blocks with two course of bricks on top. This will give You a 600mm high wall. Give a little bit of thought to how You want to finish the top of the wall off. Will You use a coping stone or a brick on edge. If going with a brick on edge personally I find it so much easier to have a 100mm cavity. As this will give You a 300mm thick wall over all.Then allow for render and fibre glass. Your brick on edge will be a brick and a half, cuts down on time to lay and cuts work spot on. Rather than only have a 30mm cavity and end up with a half bat three quarter around the top. Every brick a cut
If the two walls are tied together with wall ties and given a day or two to cure no amount of concrete will blow the walls.
Hope I have been of help, I am also a bricklayer, and since taking a change in direction to more pond building. I use this method on every pond I build. Never had a problem just very happy customers
Are You going to fit a window as well. In for a penny in for a pound

[rappy]

I would agree with thorny,by saying having a skin of brickwork as it looks a lot better than rendered walls,but then its cost again.Have to disagree with throny when he said "the blockwork skins wont blow",well i hav had it happen to me.Dont forget brickwork stays 'green' for a few days.

Anyway on my experience 'Thorny' is never wrong as on a pervious post about bead filters,he said my Aquamax 10 pump was a low pressure pump which wouldnt back wash my filter properly,well some else popped and agreed with me.By the way my Aquamax has been doing its job for 2 and half years now with no problems

[Thorny]

Oh dear this wont help the fellow with His blockwork.
Just a note an Aquamax is a low wattage pump, an Aquamaxi is a high wattage pump.
Give the walls a few days to cure as I said. They will not blow!!!
Make sure both skins are tied together with a cavity tie,Personally I would go with a HR4 space every 450mm vertical and every 750mm horizontal
Thanks for pointing out that I am never wrong, I am with some stuff, never with brickwork been doing it far to long, I have forgoten more than most know
Justin

[Jules]

Swings and roundabouts with costs. asthetics are also another isse. I prefer a nice facing brick but alot of people want the cheaper option of blocks and render. @ skins with a 1 inch back fill of compo as you work has never failed me so far! Also by the time you render the pool and wait for weather the blocks have set.

All depends what your budget is at the end of the day.

Like all things pond wise there a million and one ways to get there your only limitation is budget.

Good luck and let us know how you get on.

Jules