DIY Concrete / Cinder Block Spa Pool Advice

[tribly]

Hello all,
I've been devouring this forum in to the wee hours of the night for several days now, searching for advice, and thought it was time I actually asked some questions.

I'm considering building a small soaking pool (what I'm calling a 'greek pool' because I got the idea when I saw a piscina in an ancient greek house, because I'm a nerd like that). The goal is 7' x 5' with 3' of water depth. The interior would be tiled. And there'd be some basic filtration. I don't want this to be a huge/months long project, but I also don't want to be maintaining the thing all the time. Looking for a balance between simplicity in construction and...well, I guess simplicity in maintenance.

My thinking right now is to use concrete blocks for the main construction. Sounds like I'll need to do a poured concrete floor first, then lay the concrete blocks for the walls with vertical rebar in each block. Then fill each block with concrete.

A few questions I have though:

1. Is the rebar and poured concrete in the concrete block walls necessary for a pool this size?
2. Any chance I could do something other than a poured concrete floor? Perhaps use concrete blocks there too? Or would it shift too much?
3. I'm building a bench around the edge of it. Was going to use cinder blocks to construct this as well. Is there a better way?
4. Should I be applying some sort of sealer to the gaps and/or entire interior. And/or perhaps plastering it? I don't want ieak and I want it tiled. How do I make that happen? I've heard using epoxy thin set / grout with the tiles might be enough. If I do need to seal it, what sort of product would you recommend?
5. Any tips on tile types to use/avoid? Ceramic, porcelain, etc.
6. Any suggestions of type or size of filtration I'll need?
7. What's the deal with saltwater clorination? Like the idea, but know very little about it. Does it make sense for a small pool?
8. Dumb question, but do I need a drain? I imagine I could just siphon out the water when draining it.

And just generally I'm looking for any advice, experience, or opinions you guys have.

Thanks!

 

[vudoo222]

Welcome to TFP. There are no dumb questions here, just continued ignorance if you do not ask. Do you have a picture or plan of what you are looking to achieve? What coping are you going to use? Flagstone and saltwater does not mix well.

 

[tribly]

Was going to have flagstone patio around the edge (not right over the water, but near it) so that's good to know. Coping will probably be either ceramic tile or some natrual stone (maybe marble to match the greek theme). Any natural stones you'd recommend / avoid?

I've got a few sketches / 3d models laid out, though might not super helpful to look at unless you're in the creators head:




Basically it'll just be a 8'8" x 6'8" rectangle composed of 16 x 8 x 8 concrete blocks stacked 5 rows high giving me a little pool of 7'4" x 5'4" x 3'4". The bench would encompass the entire thing and would be both 16" high (from the floor) and 16" deep (again, composed of 16 x 8 x 8 concrete blocks, stacked 2 high this time).

 

[jasonknox]

I believe the hardest part of your job would be water proofing the block and joints. I would say yes to a poured concrete floor and no to a block floor. I do believe that you need to pour the cells of the block walls if for nothing more, piece of mind and stability because you will have return jets coming thru as well as possibly a skimmer. If this were my project I would consider a poured concrete wall joined to the concrete floor with a some sort of water block. There is a more formal name for it but I can not think of it right now. I built my pool out of concrete blocks with poured concrete in the cells and I had rain water coming thru. Maybe plaster would take care of it, I am not familiar with that as my pool was vinyl.

 

[SunnyOptimism]

Question - have you compared the price of all your building materials to the cost of getting a gunite crew to just make the shell out of continuos steel-reinforced concrete?

The biggest problem is see with using cinder blocks is that you'll have to ensure every joint is water-tight or else you will be exposed to leakage and seepage. As well, the ground around your pool will shift over time (especially the first few seasons after construction) and there is a much greater chance of cinder blocks splitting at a joint than a continuous shell cracking.

I really like your idea of a soaking pool but I really think your use of cinder blocks will be a major flaw in the construction.

As an example, we have a small waterfall on our property separate from our pool. It consists of a lower pool and a raised upper basin with a pump between them. The lower pool is maybe 4ft in diameter and about 3ft deep. It was constructed from a solid concrete shell with rebar.

Cinder blocks are good for making walls, not for holding back water.

Also, did you check your local pool building codes? I'm not sure cinder blocks can be considered as an adequate building material for a pool wall that has to provide shape, structural reinforcement and retain water.

 

[jblizzle]

There are many threads discussing building pool with cinder block [check out the search function] ... including Dave the forum owner: http://www.troublefreepool.com/threads/10154-An-unusual-pool-build

 

[vudoo222]

If you use cinder blocks on footers, consider using tar on the backside to prevent rainwater leakage into the pool. And yes you will need to pour concrete into the cinder blocks with rebar to reinforce the walls.

 

[gwegan]

I strongly recommend you look at Dave's thread set forth above. He uses concrete block walls with a vinyl liner. Liner's are not common on the west coast but you can order one custom.


Unless you are planning to do this on the qt you are almost certainly going to need a building permit and that permit will probably require a structural engineers stamp.

There are pool engineering firms that specialize in pools so if you go that route I would talk to them and some local engineering firms. The pool guys are in California but have Oregon licenses.

Have fun and post pictures. Oh give us a narrative of what you are doing, its a helpful learning experience for all.

 

[CUTiger78]

Have ya seen Bob2112's Concrete Block Puppy Pool thread from last year?

 

[Augie56]

What you're describing is about the same size/shape as a standard residential septic system tank. A 1000 gal rectangular tank is about 8' by 6' by 54" deep. They build them out of continuous cast concrete....you could probably buy one and have it delivered/set right where you want it, then all you'd have to do is tile the inside, install the plumbing and you'd be ready to soak!

 

[tribly]

I believe the hardest part of your job would be water proofing the block and joints. ... I built my pool out of concrete blocks with poured concrete in the cells and I had rain water coming thru. Maybe plaster would take care of it, I am not familiar with that as my pool was vinyl.

Do you mean that water was leaking in from the outside/ground into the pool and that you think perhaps having a liner (perhaps even outside) would be a good idea? I'm really trying to avoid having a liner on the inside (unless it's something permanent I can tile over).

 

[tribly]

Thanks all for the help and thread suggestions.

I strongly recommend you look at Dave's thread set forth above. He uses concrete block walls with a vinyl liner. Liner's are not common on the west coast but you can order one custom.

I'd already looked through Dave's a bit. Seems he did something very similar, but on a much, much larger scale. Was hoping a smaller scale meant I could be a little more lax on some of the construction stuff, but sounds like it'll be smarter to just do the job right (poured floor and filled walls).

Unless you are planning to do this on the qt you are almost certainly going to need a building permit and that permit will probably require a structural engineers stamp.

I may or may not be doing it on the qt. I couldn't possibly say.

Have ya seen Bob2112's Concrete Block Puppy Pool thread from last year?

I hadn't seen this one before, but it looks a lot like what I'm planning (except his is a bit bigger and above ground). The stuff on how he sealed it and the bonding will definitely be helpful in later stages.

Question - have you compared the price of all your building materials to the cost of getting a gunite crew to just make the shell out of continuos steel-reinforced concrete?

Haven't looked and I've heard the same thing elsewhere. Probably dumb of me not to consider it, but I'm a stubborn DIYer who likes to do everything himself.

The biggest problem is see with using cinder blocks is that you'll have to ensure every joint is water-tight or else you will be exposed to leakage and seepage. As well, the ground around your pool will shift over time (especially the first few seasons after construction) and there is a much greater chance of cinder blocks splitting at a joint than a continuous shell cracking.

Not good to hear. I've read about a few cinder block pools which seemed to hold up just fine, the puppy pool for example) but that was above ground. The others I"ve read about either use liners (like Dave's) or seem to need a new coat of waterproofing stuff ever few years (example: http://x.havuz.org/viewtopic.php?f=49&t=3259&sid=000745ed2b5cb638b0263d0e3cebef79&start=10).

Looks like, if I want to do this, I need to feel confident that I can both seal the cracks and minimize how much the blocks would shift. Anyone have any experience with either of these?

And, crazy idea of the day, what if I used cement backer board in the construction (just finished building a shower so I have it on the brain). Maybe I could place it on the interior, covering the cinder blocks, then seal it up as you normally would. Granted, showers/CBU aren't meant to hold back 900 gallons of water, but it'd have a concrete block backing it up, they are meant to be waterproof, and with the walls being larger single pieces (3' x 5') instead of small cinder blocks (18" x 8") might mean shifting would be less likely?

Anyway, thanks again for everyone's help (even if you tell me what I don't want to hear). Keep it coming.

 

[Augie56]

Buy a pre-cast concrete septic tank or catch basin in the size you want, dig a hole in your yard to accommodate it, have it dropped off in said hole, tile the inside, install plumbing and be done! These things are designed to hold water, therefore they should be watertight to begin with and you certainly won't have to worry about the wall shifting on you.

Or you could just buy a hot tub, fill it with water, plug it in and enjoy.