base of pool / footins

[ytnom]

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...

[jazzman]

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

[ytnom]

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!

[ytnom]

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

So it's even better then zeolite. Must be pretty impressive then...

[jazzman]

It is, it really is

[basjke]

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?

[jazzman]

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.

[jazzman]

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.

[basjke]

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

[jazzman]

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.

[basjke]

Thanks for the explanation Jazzman.