Raised wall construction question

[msm stl]

My pool is designed into a sloping yard. In the deep end, the water is below grade, with a stone veneer faced wall above water, sheer descent waterfall coming out below coping, and ground level deck at the level of the coping, 24 inches above water level. The sides step down, and in the shallow end, the water level is 12 inches above surrounding decking, with stone veneer on the exposed exterior wall.

My question is this. Excavation is done, rebar is in, & they're about to shoot shotcrete. Instead of building steel & shotcrete up to grade level in the deep end, so that the above water portion of the structure is constructed at the same time, he is making the pool bond beam all one level. The wall at the deep end (basically now a retaining wall) is to built out of concrete blocks on top of the bond beam. Is this OK? Wouldn't it be easier & stronger to shoot it all out of shotcrete so that it is all structurally one piece?

 

[nuklhed]

This is an excellent question, and Poster deserves kudos for raising it. I am a retired lifetime builder and witness to decades of history. In my humble opinion constructing in one piece is the only way to go. Your pool man is simply trying to save a bit of time and money by not erecting a falsework to support the gunite process, which delivers quite a lot of impact and shock. However, concrete block is porous and if you irrigate behind that wall (or even if there is significant moisture in the soil) you are likely to see lime deposit seep out behind your finish surface over time. And changing materials always carries risk of minor flex and shift between them, resulting in hairline cracks, aggravating that condition. There's also no way to gain a perfect bond between the grout (presuming he intends to grout all cells) and the vertical rebar, particularly at their base where they rise out of the gunite, so that line will present a longterm oxidation risk, especially since it's near waterline. Dunno which area you are building in, but I live in the desert and even in our dry climate I would not feel confident in a cold joint at waterline.
YES, the bond beam needs to be where he has placed it, that is good practice and I think your builder is doing all the right things. But I believe you will have a far more reliable final product if the gunite shell is monolithic everywhere... even if the stem wall is outside the contract and you have to cough up a few extra bucks to get it done your way. The top few inches of that extended wall should be thickened a bit too, another couple inches in x-sec would be nice, and double the rebar inside that.... creating a secondary minor bond beam along the top edge. Two feet of retainage presents very little in horizontal loading, but the idea is to retain the one-piece "eggshell" quality of a gunite structure. Then you'll have an assembly that will resist almost anything Mother Nature can throw at it, for as long as you live there. And if you live in a freeze/thaw zone, those forces will be formidable.
I make these comments in pursuit of a final product that will never present structural problems over its lifespan - and yours. Spec.builders don't bother with this level of care, they generally attend to the minimums and usually get by okay for the first several years. If that's your time-window too, then consider the extra cost and trouble accordingly.

 

[msm stl]

I appreciate the information. If my PB will only do the block wall, what should I look for or ask about to ensure that it is as reliable as possible?
I'm in St. Louis. Plenty of freeze/thaw cycles. The area behind the raised wall may also have to handle a moderate amount of drainage, as it's downhill from my house. (Although a lot of the area is covered by poured concrete decking).