building a new swimming pool .... must it start with cement blocks?

building a new pool ....  a couple of local contractors and one company in guadalajara said ... we (meaning us/ the owners) dig the hole and then, using cement/concrete block, we build walls and a floor for the pool.  Today, with a brand new signed contract (reviewed by the attorney), the contractor said that if I wanted the size of the pool (water portion) to be what was in the contract, they had to remove one or two walls of the block foundation.

I quickly checked with a couple of people ...  and got the usual "kinda/sorta" definitive answer.

So I'm checking here for other experiences .....

Ultimately, I was told that the cement/concrete blocks are not needed.  That it was sufficient to install the rebar and poor concrete .... and that's it.

At this moment ...  the contractor will rebuild the walls if I insist ....  which was gracious of him.  But, I don't want to do that unless it really is necessary .....

I'm hoping to get comments based on experience or first-hand knowledge ...
THANKS!!

Not sure what you mean about the "rebar and poor concrete" comment. The walls of the pool can be done in rebar reinforced concrete (providing the contractor has access to the forms to do this) OR with concrete blocks that have rebar reinforcement and concrete in the voids (if the contractor does not have access to forms). Either is perfectly acceptable. The most important thing if it is a below ground pool is the backfill around the outside. Ensure it has little clay content and does not retain water - possibly use a weeping tile along the base to prevent any "push" from water against the walls.

thanks .. my typo "poor" ... should have been poured. So, I meant rebar reinforced concrete. The rebar will be put in place and then a truck will come and 'spray' (I think that's the correct term) the concrete. The contractor said the rebar and concrete is 18cm on the sides of the pool, more on the bottom. The pool is below ground. The base is pretty much rock, large ones surrounding the pool ... but there is clay. So, I'll followup with your comment and double check with the contractor. THANKS.

Sounds like your contractor knows what he is doing. All I would suggest is pay close attention to the behind the wall drainage. Not a strength of construction techniques here - it never rains right?

The pool is close to the boundary wall. When putting in the boundary wall, we had lots of PVC added for drainage ... and we have already planned for a drain from one side of the pool that drains out beyond the boundary wall. Thanks for the input. I just needed some confirmation from other than the contractor ... some have an idea of what they are doing and others nada. Since I don't have experience in this area, i needed additional input. Thanks!!