Concrete Pool construction on Sand - pls help

[matt1]

Good morning dear forum

This is my first post here, and before I ask my question, I want to introduce my pool background very briefly.

I am quite a pool newbie, without hands-on experience. What I know in the field comes from the (in the meantime quite intense ) studying the information available on the net.

At the same time, I’m very aware that it is super important to network with people who have practical experience, and that is why I am writing today to you.

Currently I am working on a house-building project in the tropics. Part of this will be an outdoor pool integrated in the terrace.

The house is situated in the dunes, the building ground is sandy. The house is built in the "Raft" method, which means a reinforced concrete column grid structure is additionally supported by a rubble foundation.

The terrace (which is level with the rest of the house floor) is 4’6’’ elevated from the ground. There is no basement, the base is filled with compressed red gravel.

The pool is integrated in the terrace. For better understanding, here is an excerpt from the plan:



The pool dimensions (inside) are as follows:
-------------------------------------------------- ----

Length: 49’
Width: 7’4’’
Depth: 4’6’’
Total amount of water 12k Gallons

Pool equipment:
----------------------
• Salt Water Clorinator (Hayward Aqua-rite 25)
• Pump: Pentair 011513 WhisperFlo 1HP
• Filter: 3 Pentair Clean and Clear Plus Cartridge CCP320
• 2 inch tubes throughout
• No heating (tropical)
• Overflow over entire long side, with drainage channel, pre-filter
• 2 Ground outflows
• Pool technology installed next to pool, also within terrace
• Inflow on the short side of pool (close to pool tech), with 2 inlets

construction:
-----------------
Due to various constraints (available materials, local knowledge etc) I’m limited to constructing the pool using poured (in-cast) concrete.

So far, I plan to proceed like this:

a) Excavate required depth (1ft), compress the ground area (sand), and fill with about 1 ft of compressed red gravel
b) Make bottom plate with reinforced concrete, 6’’ thick
c) Create 3 of the side walls with reinforced concrete, 8’’ thick
d) Use the house side as a side wall (it leans against the compressed gravel, so statically, I don’t expect complications)
e) Use plaster to even out everything, and create a smooth surface
f) Paint the walls with Epoxy (probably 2 coats), to limit erosion/ calcium diffusion
g) Use tiles for the floor



My questions to you:

1. Is a gravel bed required? Is additional foundation (e.g. rubble) required for the walls?
2. If so, is 1 ft of compressed gravel enough as foundation of the bottom plate?
3. Is the base plate dimensioned correctly? 6’’ ok?
4. Are the side walls dimensioned correctly? 8’’ ok
5. Any objections to use the house foundations as sidewall for the pool?
6. What type of plastering should I use to keep things waterproof, smooth, and not crumbling?
7. Do I need to use expansion joints for the concrete?
8. If yes, what is the best way to seal them?
9. Can I use normal Epoxy for painting?
10. Anything special to respect for the floor tiles?



Thanks so much for your answers, suggestions and inputs.

Best, Matt

 

[Charlie_R]

Welcome to TFP!

While I may not be able to help you with your question, I'm sure someone here may be able to.

 

[gwegan]

I'm neither a structural or soils engineer, but I have some thoughts.

My first thought is you invest some cash and hire an engineer. They cost less than you think. Especially if you have soil tests. Pool Engineering in Anaheim California is one. Give them or one of the other firms involved a call. They can answer your questions better than most folks on here.


1. Is a gravel bed required? Is additional foundation (e.g. rubble) required for the walls? I suspect a well compacted bed of something is probably required but I don't know the properties of the gravel or the sand so how deep I don't know.

2. If so, is 1 ft of compressed gravel enough as foundation of the bottom plate? See above.

3. Is the base plate dimensioned correctly? 6’’ ok? Concrete pools in the US are engineered with rebar Ie#3 on 12" centers and a band of rebar along the top. The idea is to create a monolithic structure that acts and stays together. So just as important as your concrete thickness is the rebar structure inside it. The thickness of the bottom is dependent on the underlying soil.

4. Are the side walls dimensioned correctly? 8’’ ok See above --- you need a well designed rebar structure and bond beam. Are you pouring footings for the walls. Vertical walls require footings. In normal US gunite pools those forces go down the curved structure to the base of the pool, with vertical poured walls the load path is different. An engineering question.

5. Any objections to use the house foundations as sidewall for the pool? I wouldn't do this without an engineer. A concrete pool is a big solid monolithic hunk. It expands an contracts differently than surrounding structures, in part because the water inside moderates any changes. So while other structures are heating up quickly the pool is gaining temperature slowly. There are other engineering reasons for keeping the two separate. Most US engineers require several feet between structures and additional rebar if a structure will be within several feet of a pool.

6. What type of plastering should I use to keep things waterproof, smooth, and not crumbling?Most Pool Plasters will do fine. You might want to consider a vinyl lined pool as an alternative.

7. Do I need to use expansion joints for the concrete?I doubt you need them, but that is an engineering question

8. If yes, what is the best way to seal them? Again a question for a pool engineer.

9. Can I use normal Epoxy for painting? Generally you don't want to paint a pool. A good plaster surface should last 15 to 20 years with good water chemistry. Half that with bad chemistry. Epoxy or pool paint will last a year or two before it needs repainting.

10. Anything special to respect for the floor tiles? Tile on the pool floor? Or on the deck floor?

 

[Just-a-PB]

Ditto,
Cheap insurance, hire an engineer to design the structure based on your soils condition.
There are lots of them out there, can probably get it done for $500.00

 

[matt1]

Good morning all,

Thanks for your input.

Regarding the pool engineer: Pls bear in mind that the construction site is not in US, so I'm doubtful someone will accept to do the job without proper first hand knowledge of the construction site. (I'll contact the guys in Anaheim anyway, pls pm me if you know someone else you can recommend)

Let's focus on the non-static questions then.

Vinyl is off, as there are loads of dogs in the area (not that they would be permitted to the pool, but you know how dogs are )

* Plastering: Can you point out what kind of additive is used to make plaster water proof (There is no specific pool plaster available in the country afak)
* Maintenance: I was under the assumption that maintenance of pool water would skyrocket if the plaster is not painted, due to Calcium diffusion and pH rise (bear in mind, I use a salt water clorination system). That's why I thought to paint the walls with Epoxy
* Epoxy paint: Are you sure that the paint job needs to be done every 2 years if epoxy is carefully applied to a properly prepared plaster surface? In my experience (not pool related) Epoxy is highly stable on stone, concrete etc
* Tiles: I'd like to do a tile mosaic on the floor. (should be better than plaster for maintenance etc imho). Can I put it straight on the plaster, or any considerations?

Thanks a lot
Matt

 

[Esiebert7625]

You sound like you have some restictions based on your locale, curious as to what part of the tropics you are in as that is a very general and vague term.

 

[matt1]

@ ESiebert: Island in the Indian Ocean