Thread: Constructing Pool, Bad Pour - Need Advice

Hi guys,

We're in the process of building our pool, we poured the pad about two weeks ago which went fine, we then poured the walls a few days ago and it was very close to a disaster!

I know you guys like pics, so here's a few before I continue my yarn -

Before wall pour:




During wall pour:



And here's after the wall pour:



Anyway let's get back to the situation that looked to be a disaster, but ended up being downgraded to a "major fuckup".

Basically we were doing the pour and the form work began to fail on one side, it bowed out in the middle and looked like it was ready to give, we stopped the pour and got every available hand in the pool with hammers and nails to add more support. The wall was supposed to be 20cm thick in the part of the near failure it was nearly 40cm now after the near failure.

So panic one over we continue to pour, then panic two, both cement trucks say they're empty, the double thick wall at the failure point has sucked up an extra couple of cubic meters. We all know that a pool pour has to be done in one go, so we had to get another truck on site pronto. The cement company really cam through and redirected a truck from another site and had it there inside 30 minutes. The mix had Sika Plastocrete in it, so there was no danger of it setting in that time (I hope).

So there we were thinking we'd dodged a bullet until we removed the form work yesterday. It looks like during all the excitement the vibrator hadn't been used in one section and we now have exposed rebar at one point, you can actually reach in and touch the rubber water stop in the cold joint. Here's a close up pic:



Ignore the zig zag line above that's just run off from where two pieces of board were connected. But as you can see we are looking at exposed rebar, not good.

Here's another pic where you can see the wall (on the right) where the form work nearly failed. It's going to take some serious render to straighten that curve out! You can also see down the bottom the exposed rebar that was in the previous close up:



As you can imagine I'm not exactly feeling confident in the water retaining properties of this pour. So to stop this think leaking, here's the plan:

1) Plug that hole with Sika Water Plug 102 and smooth over any rough edges from the pour.
2) Add two coats of Sika Topseal
3) Render the whole surface ready for tiling with Sika Latex

I know we've got a few pool buffs on here so I would love to hear your feedback on that plan or any other ideas to prevent later leakage.

How about casting a new wall on the inside of the existing faulty wall? Use the existing faulty wall as "formwork" for the new. Doesn't need to be thick, as you already have strength in the old one. Just thick enough for water-tightness.

Originally Posted by weewillywinkie

How about casting a new wall on the inside of the existing faulty wall? Use the existing faulty wall as "formwork" for the new. Doesn't need to be thick, as you already have strength in the old one. Just thick enough for water-tightness.

That would work probably work but is a bit of a sledgehammer approach. I think I might perform step 1 first in my idea above, then test fill the pool and see if it leaks. If there are some small leaks then we're probably okay as the next two layers of sealant will likely plug those small gaps.

I hope you didn't pay for that mess!

Could you make the rest of the walls curved to match?

Call the curve a feature.
Never seen a form poured pool. In oz the would spray.
I think as long as your fill is solid enough to support the sealant at whatever psi your going to have down there you should be ok.

Originally Posted by The Fresh Prince

Could you make the rest of the walls curved to match?

Getting the curve out is easy, we just loose 10-20 cm of pool length. Water retention is my concern. At the moment I still have full access so can choose my products and approach carefully, things won't be so simple once sealant, render and tiles are down.

Honestly I'd dig it out and start again.

Originally Posted by Necron99

Call the curve a feature.
Never seen a form poured pool. In oz the would spray.
I think as long as your fill is solid enough to support the sealant at whatever psi your going to have down there you should be ok.

I'm a software engineer by trade, a lot of "features" get built that way!

That's what I was thinking. The pool's only 1.2m deep so we're not dealing with that much pressure. Half the pools in this part of the world get poured without a water stop in the cold joint and no sealant layer so I'm probably over reacting.

All the best with it Chris , interesting pics

All the Silka products are tops in their field, but won't remedy this cluster-fuk.
The rebar should be at least a third within the poured concrete, not near or at the surface as the pix show. Water escape will undermine not only the pool but likely your house and wall. Breaking that pour will be costly and nigh on impossible.
FWIW, I'd pour another pool within the perimeter of this one as WWW recommends at #2 above.
Can't tell, but did they pour footings before laying the floor. If not, break footing holes in the existing floor to pour the footings. If floor is weak remove completely.
And bring in new thai pool experts after checking their previous work and customers.
As a French officer once exclaimed: 'That is a good predicament!'

Originally Posted by daveboy

Honestly I'd dig it out and start again.

Water is so cheap here that this pool would need to leak about 30,000 m/3 of water before I would see a return on that investment. Seeing as the pool only holds 35 m/3 of water and it's sitting in soil with a very high clay content I fear that might not happen within my life time.

Nice sized fish pond, gunna look awesome with a heap of decent sized Koi in it.

Originally Posted by tango

All the Silka products are tops in their field, but won't remedy this cluster-fuk.
The rebar should be at least a third within the poured concrete, not near or at the surface as the pix show. Water escape will undermine not only the pool but likely your house and wall. Breaking that pour will be costly and nigh on impossible.
FWIW, I'd pour another pool within the perimeter of this one as WWW recommends at #2 above.
Can't tell, but did they pour footings before laying the floor. If not, break footing holes in the existing floor to pour the footings. If floor is weak remove completely.
And bring in new thai pool experts after checking their previous work and customers.
As a French officer once exclaimed: 'That is a good predicament!'

Thanks for the feedback! The rebar is 2.5cm from the surface, there were 2.5cm concrete stoppers placed all the way around. The walls are 20cm thick, that hole goes in about 10cm in at the worst point as I can touch the water stop. It's only a small section of the pool with this problem and the walls and pad were over engineered to allow some wiggle room for fuck ups so I'm not concerned about the structure only water retention.

So you don't think that a couple of coats of Sika Topseal plus 5cm of render with Sika Latex will hold water in this case? Or are you more concerned with the structure?

Also would a pour inside the existing pour solve the problem as there would be no water stop from the new inner wall to the pad?

Originally Posted by daveboy

Honestly I'd dig it out and start again.

If you don't do it properly you are really gonna regret it in a few years when the tiles start bulging.

Mark

Did you pour a "mud slab," before pouring the floor?

Is there a water seal below the floor and walls?

The exposed re-bar in the picture also looks as though you have a large "cold joint," in that portion of the pour?

With a water seal in place prior to mud slab or wall pours it insures that external migration of water will not affect the pour and set concrete in the future. sometimes called a vapor barrier.

When you made your floor slab pour was it done in conjunction with the walls? The joint between the floor and the walls should have had a water seal as well.

With the blow out or void along with the cold joint it should all be hammered out. Once completed, re-form and re-pour. Insure that "all," re-bar is clean and free of rust prior to pour.

What size vibrator did you use? I would think that 3/4" -1" dia. would do nicely. don't let the vibrator rest in place more than a few seconds and make sure it begins from the first moment of the pour as as the height rises the ability of the vibrator to penetrate the concrete decreases. Over vibration can cause blow outs as is possibly one of the reasons for the wall failure.

Plasticizer or super plastiziser does not guarantee the water retention qualities of the mix, but allows the mix to set or be held for longer periods depending on mix temperatures and other variations.

If its wrong to begin with, my advice is do it right. There's no substitute.

You will no doubt be tiling this pool later. Floor and wall variations will cause costly special cutting of tiles to fit error locations.

Offered as an alternative to other suggestions.

Good luck.

Pools seem like more trouble than they're worth. Pretty much everyone I know with one has either had installation or ongoing maintenance woes with them.

That being said I know 5/8th of feck all about anything to do with them so good luck, hope it works out!

Originally Posted by Katana

Originally Posted by daveboy

Honestly I'd dig it out and start again.

If you don't do it properly you are really gonna regret it in a few years when the tiles start bulging.

Mark

I'd agree.

You have a team building it? And they messed it up? Surely you say to them "start again you idiots; dig it all out and sort it".

Now I'm no expert in building, but I do seem to think that as it is so close to the house, leaking water might have a nasty impact on the house and not just be the cost of topping up the pool.

Thanks for all the comments guys, it's much appreciated and lots of food for thought!

I'm confident in the engineering, the design was done by one of my staff. Although he doesn't usually design pools, he spends his days designing small bridges, culverts, levies and dykes for irrigation systems so he's quite aware of the power of water and I'm pretty sure when you're doing something for your boss you're going to double check your number and go over on everything.

But here are the details anyway as I remember them. The soil around my house has already been tested, it's very solid with high clay content, the house you already see in the background is two floors with a third floor in the roof, it didn't require piles and sits on pads.

After the hole was dug out for the pool large hardcore was distributed evenly at about 20cm deep then covered in cement. The 15 cm pad was cast on top of this base with a two layer 15x15cm rebar grid, with the lower layer 2.5cm about the base and the top layer 2.5cm below the top of the pour. The concrete was a strong mix with 8 bags per cubic meter and Sika Plastocrete added accordingly. The poor was made with the vertical rebar for the walls in place.

The walls were inset from the pad by about 30cm. The walls are 20cm thick with the same 15x15cm grid as the pad. There was a 15cm water stop positioned in the between the vertical rebar for the walls in the pad so that 7.5cm was in the pad and 7.5 sticking out from the top. The water stop required two joins, both were heat welded.

After the pad was poured the vertical rebar had moved inwards at one point (the point that's now exposed). The solution to this was to make that wall 5cm thicker (25cm) so that the rebar was at least 2.5 inside the wall. For the wall form work, the back was a brick wall, the front was plywood.

When the pour began the pump controller was too trigger happy and began pouring unevenly. This caused the form work to move. It appear to have pushed back the extra 5cm added on the side that wasn't straight (as mentioned above) and added 5cm to the opposite side (I can tell that by measuring and looking at the trap). As I said earlier part of the form work nearly failed, this was an unwelcome distraction and the end result seems to be that the exposed section wasn't vibrated thoroughly enough. The part where the failure happened is no problem, that's now about 40cm thick, so no worries there!

In terms of blame, it's on everyone in part. It's the concrete supplier for being in too much of a rush with the pump, it's on the contractor for the form work starting to give. It's on me for hiring a contractor on time only with me supplying the materials.

The rest of the poor with the exception of this section looks sound. The problems as everyone here has said are two fold. First will it hold water? It doesn't matter if 98% of the pour is sound, a leak only needs 1%. The second problem is that those rebar are too close to the surface and will rust and stain the pool unless handled correctly.

I'm not sweating over the rebar pool stains are a common problem with well documented solutions. The leak is the problem, I'm not worried about waters effect on the structure, the water table here is about 1m below my lawn in the wet season, so the footing are going to be surrounded in water every year regardless and I've got engineers I trust with soil tests in hand all telling me that with the soil we have under our house that's fine.

I think the next step is to till the gaps with Sika Waterplug, then wait 30 or so days for the cement to fully cure, then I'll fill the pool and do' the bucket test to see where we stand. If we're loosing a little I'll probably stick with the plan in the original post and hope the two remaining layers of sealant do their job. If it's loosing a shit load then back to the drawing board with either secondary pour within the existing pour or the fibre glass option from DrAndy.

DrAndy how much did the fibre glass coat cost per meter roughly?

Learning curve !

Originally Posted by Wizard of Oz

PS. Is there any plumbing and lights in the pool? How do you filter the water? From the looks on the pictures looks more like a pond then a pool, but maybe I missed those features through the camera angle.

The plumbing and electrics were designed by a Dutch friend as a favour, he usually charges more than I can afford and usually works on things much more grandiose than garden pools. Their are four jets in the floor each attached to heat welded PPR pipe and a trap that's not visible in any of those shots, with Sika Flex surrounding the penetrations. The lighting is all multi-colour LED strips (whites, yellows and oranges) that will be laid under the lip of the tiles on the pool edge and cover the whole circumference, they'll be controlled by a PLC and change shade and pattern in a soothing rhythmic way rather than disco style.

For the system we've got an Onga Chlomaster salt water chlorinator, a Pentair Optiflow pump and an Emaux sand filter.