Above ground pool, concrete base

[Crossy]

We are thinking of getting a low(ish)-cost above ground framed pool, something like this http://www.pattayapools.net/index.php?option=com_content&view=article&id=102%3A56955-o-24-ft-732-cm&catid=35%3Ametal-frame-pools&Itemid=53&lang=en (just as an example).

Since our land is - a. Not very level and b. Prone to the occasional flood (apart from cost one of the reasons not to have an in-ground pool) I think we should build a levelled concrete pad, probably tiled (cheapo tiles) too.

Assuming the pad will have steel reinforcing mesh (6"?) and some 1m piles scattered about how thick should we make it 100mm or maybe 150mm?

Pad will probably be a 10m x 10m octagon (4.1m side).

Thoughts on this plan, pull no punches, I'm an engineer but my degree is in Electrical and Electronic Engineering.

[sappersrest]

These pools are not normally put on a concrete base but a bed of sand.

http://blog.poolsaboveground.com/put-ground-pool/ A good article I just found on the web explains.

Might be worth firing of an email to intek and see what thy would have to say about it.

Good luck

[Dario]

If you ask Intex their FAQ say:

Can grass grow through the ground cloth and / or pool liner?

Yes, in some cases certain types of hardy grass such as Bermuda or St. Augustine can grow through the liner. Before setting up your pool, it is recommended that you clear the area of these types of hardy grasses. INTEX will not be held responsible for grasses that may grow through the ground cloth and / or pool liner, as this is not a manufacturing defect. A ground cloth or tarp may be helpful in preventing this from occurring.

IMHO, a 100% levelled tiled floor has always been the best. On that tiled floor you lay the ground cloth you get included with any Intex pool set starting at 15 ft diameter. On such an underground no damage can ever occur to your pool.

As for the height of the pad I really can't tell you. Mind you the pool you intend to purchase holds 47'241 litres of water at 90% filled. Eventhough your tab will be reinforced with steel mesh, 10 cm might be not enough, because there is different kinds of steel mesh. I remember when I once let redo my driveway at my then townhouse in Don Muang, I saw what strong steel mesh the contracter used. I remember very well that he said to me: you never have to worry, you can land a B747 on this. To conclude, I think a 10 cm pad wih the correct sized reinforced mesh would be enough, but for piece of mind I increase that to about 12.5 cm. Adding 2.5 cm won't ruin you but ease your mind. Mind you Crossy, I'm far away from an engineer, I was a certified public accountant ...

Edited October 11, 2015 by Dario

[Crossy]

My chief worries since this will be a semi-permanent installation is something growing through, movement (both horizontal and sinkage) of the legs and damage to the pool during gardening activities (man with a brush cutter).

The main issue for me, not being a structural engineer, is that the full pool will weigh more than 47 TONS, ok spread over 42m², but that's still 1,200kg per m².

How thick should I make the pad, it's resting on well compacted fill? Does it need piles, even our garden path and ghost house have 1m hexagon piles?

EDIT Ah I see Dario has added to his post above, thanks for that, I think we're on the same page here.

EDIT 2 A bit of Googling is suggesting a 4" (100mm) pad, so I think Dario is spot on

[Dario]

My chief worries since this will be a semi-permanent installation is something growing through, movement (both horizontal and sinkage) of the legs and damage to the pool during gardening activities (man with a brush cutter).

The main issue for me, not being a structural engineer, is that the full pool will weigh more than 47 TONS, ok spread over 42m², but that's still 1,200kg per m².

How thick should I make the pad, it's resting on well compacted fill? Does it need piles, even our garden path and ghost house have 1m hexagon piles?

EDIT Ah I see Dario has added to his post above, thanks for that, I think we're on the same page here.

For your garden path and gost house you let implant piles? It surely wouldn't hurt to add them. 1 m hexagon tiles can't cost so much. Well since I'm not a structional engineer, I can't tell. You might have to wait for more input from other TV members. There might be some who are able to help, or architects. Wish you good luck.

Edited October 11, 2015 by Dario

[Longtooth]

You can do stronger than mesh by simply making your own rebar grid with 3/8" rebar. 9" or 10" squares would be nice and strong. Put "dobies", little blocks of concrete, or half a small red brick scattered around under the intersections of the rebar...enough to hold it off of the dirt and let concrete fill under the steel. Steel lying on the ground is useless. The steel should be in the middle of the vertical depth of the concrete. Concrete is cheap for that sized pour. When you wire the intersections of steel together, bend the twisted ends DOWN. Bend a rebar in a circle at the perimeter to hold it all together. On this circle piece, overlap the ends a couple of feet. Use a very strong concrete mix. Quality always satisfies in the end.

[Chaichara]

1. Crossy does not state which of these products he is interested in but somewhere later he mentions 44 ton so I assume it to be the big one.

2. All these Intex pools can be purchased on line much cheaper from Lazada (where the named supplier is probably also getting them from). Also, SwimmigPoolsThailand stocks some of them, but the identical ones marketed under the Jilong brand. When I looked last, they were also quite cheap, in fact I bought a 3.6m inflatable from them last year. GlobalHouse also has a line in large, steel-walled vinyl liner DIY pools for about Baht 59,000.00 complete with accessories. The kit is on a pallet and weights about half a ton.

3. For an inflatable pool , just level the land with sand and put any heavy duty plastic sheet over it.

4. For a 44 ton pool, lay either a level 10cm thick concrete base, using rebar DB9@20 (that means a 20cm mesh of 9mm rebar, tied with proper binding wire, and with the rebar ends curled over so that they are totally encased in the poured concrete). Add a little waterproofing additive (nam ya ganseum) to the concrete. Put some plastic sheeting on top of the concrete when it has cured, and put the pool on top of that. OR just level the land, put 5cm pre-stressed concrete planks down and drift a level 5cm layer of concrete on top of them over standard wire mesh reinforcing . As a reference, I recently built a 60m driveway to my house using compacted gravel on dry clay substrate, 10cm 'Steng' 180 concrete on a rebar grid DB12@20. It takes a fully laden 10 wheel truck, bearing in mind that the load points are on the small footprints of the wheels. For a pool, the load is spread evenly everywhere.

5. Getting a custom above ground concrete pool built will cost many times more - probably well over Baht 100,000.00 if sdone by a bona fide pool constructor. This would of course be a very permanent solution but you would have the advantage of having a proper filtration system, underwater lighting, and any other plumbed-in accessories such as Jacuzzi jets or a salt water chlorinator. You could build such a pool yourself and save 20 - 40% of the cost but you would need to be aware of the special construction methods and correct way for laying tiles (which is the only reasonable solution for covering the concrete inside). If you buy all the technical equipmenty from one supplier, they may give you some free advice and even plans and specifications. You have to ask around.

[IMHO]

My chief worries since this will be a semi-permanent installation is something growing through, movement (both horizontal and sinkage) of the legs and damage to the pool during gardening activities (man with a brush cutter).

The main issue for me, not being a structural engineer, is that the full pool will weigh more than 47 TONS, ok spread over 42m², but that's still 1,200kg per m².

How thick should I make the pad, it's resting on well compacted fill? Does it need piles, even our garden path and ghost house have 1m hexagon piles?

EDIT Ah I see Dario has added to his post above, thanks for that, I think we're on the same page here.

EDIT 2 A bit of Googling is suggesting a 4" (100mm) pad, so I think Dario is spot on

A 10cm thick ground slab can support well over 2 tons/sqm with 20cm grid spacing using 4mm steel/mesh, or ~500kg/sqm if suspended. Consider what's going to happen the the soil underneath it. If you can compact it down with sand first, 10cm should be fine. If you think there's a chance of erosion, up it to 15cm and use 6mm steel.

One more thing - consider going deeper than 1.2M... you'll be surprised how shallow that feels, especially as water levels 'ebb' before refilling. You'll also want to be able to make plenty of shade over a pool this shallow, otherwise it'll feel more like a bath in the hot season

Edited October 12, 2015 by IMHO

[Pacificperson]

Personally, I would be less worried about the concrete and more worried about the soil underneath it. Ask the guy who built your house.

[Crossy]

The house is on 16m driven piles, not going to be doing that for a portable pool.

We have 1.5m of well settled (5+ years plus the 2011 flood) fill, I suspect that no piles or just 1m like we have under the path and ghost house will be the way to go.

[sappersrest]

Hi Crossy if you remember back to the the days in the old country there was such a thing as raft foundations can't remember the specs but i am sure with a bit of research or help from civils types you might find that these may help.

[Crossy]

Thanks for all the above info chaps.

I think we are going to go with a 100mm reinforced pad on a thin sand layer to avoid disturbing the fill which is well settled by now.

If it does sink I expect it to be reasonably even so everything stays level.

We shall see.

[blackcab]

Our pool is 1.1m deep and for me that's deep enough to swim in and for the wife to do water exercises.