base of pool / footins

Any thing to do with swimming pools, fish ponds, or other man made structures which hold water (but not wells for drinking water).

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base of pool / footins

Postby ytnom » Thu Dec 24, 2009 9:31 am

It seems to be hard to find info on how to build the support part of a pool.

Some pool companies just poor a floor slab (if depth of pool is above water table).

Some pool companies pile.

Some pool companies put in footings and beams on which they poor the floorplate.

What would be the best way long term, but also most cost effective for a 50 sqm pool, 1.3 m deep on average, assuming floorplate level is above the water table, and installing hydrostatic valve(s) to allow for rising water table in rainy season...

All the pools I have seen built with just the floorslab (no footings nor piles) are doing just fine 6 years down the line, some up to 90 sqm, all with a maximum depth of about 1,7 meter...
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Re: base of pool / footins

Postby jazzman » Thu Dec 24, 2009 10:29 am

A truly professional pool building company will put down either piles or footings with an H-shaped beam, or for a longer pool, a cross-bar beam every 3.5 - 4.5 metres. They will never just pour a slab without any underpinning. If you a re doing it yourself, you can take the risk. I built my first pool in 1974 without absolutely any knowledge whatsoever - it didn't even have any plumbing or a filtration system as it was expected to have to change the water every couple of weeks! It had a flat concrete bottom and no beams or footings, but it is still in use today in spite of extreme seasonal changes in temperature. It is drained throughout the winter. (Hambühren, Landkreisreis Celle, near Hannover, Germany).

Don't forget the extra cost of rebar in the footings and beams. A standard 20 cm thick floor plate should have two levels of 12 mm rebar (DB12) laid in a 20 x 20 grid. 'bar-chair' spacers of RB9 keep the two levels 10 cm apart.

Don't forget the water-stop in the join between the floor plate and the concrete walls, and excercise all the recommended caution with all the pipes and electrical conduit that goes through the concrete walls - there's a right way and a wrong way of doing this.

Correctly calculate the capacitly of the pump and filter that you will need - and DON'T get ripped off with the price: around 22,000 baht should be the absolute maximum for a complete pump and filter combination pool your size. be absolutely sure to use special 13.8 grade PVC piping (NOT 8.5!) and accesories throughout, use wide radius bends (not 90° angles), and use the special glue, not that ordinary liquid stuff for standard PVC pipe. Break the glaze with very fine sandpaper on the outside and inside of all part to be joined before applying the glue. he glue sets immediately - you don't get a second shot to tweak anything. If you can afford an extra 3,900 baht, used crushed SO2 crystalls filter media rather than silica sand, right from the very start.
Pressure test all your plumbing before you backfill any dirst.

Finally, read ALL the threads in this swimming pool forum :D
How to build a $20,000 / £14,000 house and a $???? MOTEL Updated 21 March 09 - with BOQ and costs
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Re: base of pool / footins

Postby ytnom » Thu Dec 24, 2009 3:36 pm

Hi Jazzman,

Thanks for the quick reply!

Believe, have been gong through a lot of the topics already :)

Footings it'll be, and as the pool will be 10 meters long I reckon 1 or two cross beams as well.

What's your opinion on Zeolite as a filter media (Zelbest etc)? I haven't used the crushed crystalls yet, but up till now have been happy with the zeolite for keeping the pool crystal clear.

Cheers!
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Re: base of pool / footins

Postby ytnom » Thu Dec 24, 2009 3:38 pm

Oops, just saw your post on Zeolite and the crystals.

So it's even better then zeolite. Must be pretty impressive then...
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Re: base of pool / footins

Postby jazzman » Thu Dec 24, 2009 6:59 pm

It is, it really is :D
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Re: base of pool / footins

Postby basjke » Fri Dec 25, 2009 12:58 pm

Hi Jazzman,what do you consider proper sized footings and how many for a pool of mentioned size.Will 40 cm footings be big enough are is this way too small?
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Re: base of pool / footins

Postby jazzman » Fri Dec 25, 2009 1:12 pm

Footings and /or piles are to stop a pool sinking. It depends on the quality of the substrate. Whether it is very hard clay - to very soft sand. It's always best to do a trial boreing in the wet season to see whjere the highest water table is, and dig the footings in the fry season to see how solid it is. On sand or sandy soil 1.0 x 1.0 minilmum, and if it is likely to get sodden in the rainy season, drive piles. For very hard clay that will remain above the water table in the wet season, you could get away without any footigs at all; In all cases however, the ground beams should be built as a reinforcement for the floor.
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Re: base of pool / footins

Postby jazzman » Fri Dec 25, 2009 1:15 pm

Footings and /or piles are to stop a pool sinking. It depends on the quality of the substrate. Whether it is very hard clay - to very soft sand. It's always best to do a trial boring in the wet season to see whjere the highest water table is, and dig the footings in the fry season to see how solid it is. On sand or sandy soil 1.0 x 1.0 minimum, and to 60 x 60 for drieer soil. If it is likely to get sodden in the rainy season, or if the pool is built in very deep in-fill, or on marsh land such as in central BKK, drive piles. For very hard clay that will remain above the water table in the wet season, you could almost get away without any footings at all; In all cases however, the ground beams should be built as a reinforcement for the floor.

Contrary to what one might think however, a concrete pool full of water is still lighter than the earth it displaces and will always tend to 'float'. It will only sink if there are cavities under it, such as could be cause by underground water currents, orthe substrate slipping to lower land somewhere.

If you build a pool on wet land, you must incorporate some hydrostatic valves to prevent an empty pool shell from popping out of the ground. Ff that happens,it will break any of the PVC piping connected to it.
Last edited by jazzman on Fri Dec 25, 2009 1:25 pm, edited 1 time in total.
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Re: base of pool / footins

Postby basjke » Fri Dec 25, 2009 1:18 pm

jazzman wrote:Footings and /or piles are to stop a pool sinking. It depends on the quality of the substrate. Whether it is very hard clay - to very soft sand. It's always best to do a trial boreing in the wet season to see whjere the highest water table is, and dig the footings in the fry season to see how solid it is. On sand or sandy soil 1.0 x 1.0 minilmum, and if it is likely to get sodden in the rainy season, drive piles. For very hard clay that will remain above the water table in the wet season, you could get away without any footigs at all; In all cases however, the ground beams should be built as a reinforcement for the floor.


Thanks for the reply Jazzman but I formulated my question in the wrong way.What I meant to ask is how deep the footings should be.Is 40 cm deep enough or not?Thanks in advance
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Re: base of pool / footins

Postby jazzman » Fri Dec 25, 2009 1:46 pm

Not a lot, if the pads a are 20 cm thick, a 20 - 40 cm stalk 20 x 20 thick should be enough if the pads are cast on relatively firm, dry substrate. Afterall, the pool is already up to 2m deep You can always do the broomhandle test.
How to build a $20,000 / £14,000 house and a $???? MOTEL Updated 21 March 09 - with BOQ and costs
Don't let this happen in YOUR house.
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Re: base of pool / footins

Postby basjke » Fri Dec 25, 2009 8:40 pm

Thanks for the explanation Jazzman.
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Re: base of pool / footins

Postby Roger Ramjet » Mon Oct 25, 2010 7:45 am

After hours of fruitless searching, days of discussions with pool people, engineers, architects and builders, I still have little concrete knowledge of the pilings/footings required for my pool. The size of the pool is about 30 cu metres... or 7mts X 3mts X 1.4mts and the ground which it will sit on is well above the water table. Can anyone tell me the answer? My pool guy says it is up to the engineer, my engineer says little, my architect just doesn't know and searches have been fruitless. My pool guy says there's not much weight because it will sit on the ground.... gees I could go on and on about what if and what for and why's but I am still no closer to a clear answer. Do I make the pilings load bearing and if so, how much load?
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Re: base of pool / footins

Postby fredlk » Mon Oct 25, 2010 8:04 am

Roger Ramjet wrote:I still have little concrete knowledge of the pilings/footings required for my pool.

Not altogether comparable, but as you have seen my house is built on pilings.
The pool on the other hand will not have pilings underneath. It will be 11 metres at its longest and 7 metres at its widest and up to 180 centimetres deep.
Engineers, architect and builder have agreed that the base of the pool will be enough foundation.
The pool will not be physically connected to the structure of the house or patio just to be on the safe side in the unlikely incidence of any movement.
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Re: base of pool / footins

Postby Roger Ramjet » Mon Oct 25, 2010 8:35 am

Fred,
Thank you for that. The pool man said that at the most there would be six small pilings/footings but they would not do much and be superfluous because the weight of the pool base would be on compacted soil already in place and that would be sufficient. What alarmed me was reading that an indoor swimming pool could weigh as much as the house, which I didn't believe, but I started thinking, and for me that is dangerous, because I have large footings (as already posted), because of the size of the house.
I have a meeting with the architect this afternoon at 1400 hrs and will post on my return.
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Re: base of pool / footins

Postby fredlk » Mon Oct 25, 2010 8:59 am

One more thing I can add.
In Holland on clay soil with extremely high levels of ground water, my house was built on one very large reinforced concrete slab of about 20 metres by 20 metres.
The weight of the whole thing and its area kept it above the ground, but if heavy trucks passed by, the whole structure trembled. (I didn't build it.)
The swimming pool on the other hand, right next to the house, was built on 8 metre long pilings. It was in-ground and 10 metres by 5 metres by 190 centimetres deep.
The pool was anchored to the pilings and the pilings were there not to support the pool, but to prevent it from floating upwards out of the ground on the ground water.
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