16 July 2024 Finishing Up my OB Pool

[Newdude]

The socket wrench is on the other side of the garage in the red drawer of that cabinet with all the grease stains …

The socket wrench is wherever I used it last as a hammer, thankYOUverymuch.

 

[setsailsoon]

Were the lintels just cast concrete with rebar or did the do any pre-tensioning ? I would think that lintels that length (10ft) would need some pre-tensioning to compensate for the sag forces. Just doing unloaded rebar seems inadequate for load-bearing member that will experience deflection forces.

Not really sure if they were pre-tensioned, I just required to the engineer's spec. I suspect they are not and are just sized and spec'd to give a maximum deflection during the max storm load. I know they have steel embedded but I don't see any fittings that would be used to pre-tension. The wind loads around here are tremendous. County requires my garage doors are spec'd for 180 mph sustained.

 

[kimkats]

cracked in the middle all the way though.

OH who saw it first?

Supplier tried to get me to agree to an epoxy repair... I think they thought they'ed get away with this because I'm an OB

Ummmmmmmm no!!!! Would that pass inspection if someone did accept it?

pre-tensioning

What does this mean?

 

[JoyfulNoise]

What does this mean?

This picture says it best -


Basically you add steel “tendons” to the cast concrete that are under tension when you pour the concrete. Once the concrete sets and cures, you release the tendons from the mold. The steel “tendons” create an additional compressive force that keeps the concrete from cracking or concrete cracks from propagating. If you place the compressive load below the midline of the concrete form, then the tendons will impart a bowing force upwards thus offsetting a load placed on top of the structure that might cause it to bow downwards. Concrete is excellent under compressive loads but cannot handle tensile loads or bending moments very well. So you want to design concrete structures so they are always under compressive loads.

 

[kimkats]

THANKS! That is what I thought but was not sure of the details. The name says it all but those pics were just what I needed to really understand it!

 

[setsailsoon]

OH who saw it first?

Ummmmmmmm no!!!! Would that pass inspection if someone did accept it?

What does this mean?

Truth is I think Robin saw it first but it was so obvious all would have seen it and the county inspector would never have passed it as is. It started with just a hairline crack about 30 min after setting. County probably would have accepted a properly designed and documented epoxy repair and a LOT of builders would do it that way... one of the best things about OB is you make quality decisions rather than defer to a conflicted builder. In many cases the owner would never even know about this kind of thing. Matt answered the pretensioned question perfectly above.

 

[JoyfulNoise]

My foundation is stamped is the garage and few other places with the words “POST-TENSION” referring to the fact that the slab was poured with tendons in place but not pre-tensioned. After the the slab cured, the contractor came back and, using some specialty tools, pulled on every tendon and locked them into tension using anchors. This imparts better compressive stress on the slab and avoids slab cracking on expansive clay soils. The downside with post tensioning is that if you ever need to cut into the slab for remodel work, you need to locate the tendons and either avoid cutting them or have a specialist come in, locate ones that need to be severed and rework the tendons with additional anchors to preserve the stress. People make huge mistakes during remodels demo’ing a slab and cutting tendons. When you do that, the stress forces change dramatically and you can send cracks propagating through out the slab. Decent contractors know to ask first if a slab is tensioned and, if it is, the job gets A LOT more expensive …

 

[TX2OBX]

the huge windows/doors on the back of the house is going to be an epic view. Excited to watch this one progress.

 

[kimkats]

the stress forces change dramatically and you can send cracks propagating through out the slab.

That is just what I was seeing in my head as I was reading that! That could be a mess!

 

[setsailsoon]

My foundation is stamped is the garage and few other places with the words “POST-TENSION” referring to the fact that the slab was poured with tendons in place but not pre-tensioned. After the the slab cured, the contractor came back and, using some specialty tools, pulled on every tendon and locked them into tension using anchors. This imparts better compressive stress on the slab and avoids slab cracking on expansive clay soils. The downside with post tensioning is that if you ever need to cut into the slab for remodel work, you need to locate the tendons and either avoid cutting them or have a specialist come in, locate ones that need to be severed and rework the tendons with additional anchors to preserve the stress. People make huge mistakes during remodels demo’ing a slab and cutting tendons. When you do that, the stress forces change dramatically and you can send cracks propagating through out the slab. Decent contractors know to ask first if a slab is tensioned and, if it is, the job gets A LOT more expensive …

Yes, almost all slabs in Houston are post-tension and I've watched that process many times. It's a little scary but it always works. The lintels are pre-cast but are not prestressed, they typically don't do that for lengths less than 14'. I found a typical cross-section for 12" lintels from the manufacturer's website and have pasted it below. The slab has rebar but no post tensioning. It's a pretty standard design around here with a large beam footer around the perimeter and additional footers installed under all load bearing columns. There's only one load bearing post in the house itself. The slab between footers is typically 5" and is cut at 10' min to relieve stress during curing to 25% of slab thickness. I randomly checked the cut depth with a credit card. The cut depths were right on the money.

Chris

 

[setsailsoon]

the huge windows/doors on the back of the house is going to be an epic view. Excited to watch this one progress.

So glad you noticed that! It's one of the key design features of the house. The center opening is a 12' wide and 10' high the slanted opening to the right is a 9' by 10' high. Both are impact resistant sliders and I'm hoping the view from the front door out the back will be exactly as you describe and overlook the pool to the lake. We've even made the attached spa at pool level instead of raised so it won't detract from the view... fingers crossed that this works!

 

[setsailsoon]

29 May 2022 Update

Folks,

It's been a busy month for us. We finally have all the structural concrete in place, roof trusses installed, plywood sheathing on, and membrane on top of that. (photo's below). Next week we start mobilizing interior trades with framing Tuesday. Then about one week apart we start A/C rough in, plumbing rough, electrical rough, and in parallel we install window bucks/windows plus stucco. Stucco is a big job on this house since we've got 12' walls and all the soffits plus patio ceilings are stucco. We should be about 70% work-in-place complete by mid July. Then the really slow interior finish trades begin. Roof tiles are to be delivered and installed late July... we hope they're on time!

While the house build progresses I'm spending more and more time on the pool. We get our first draft of detailed design drawings next week. I know they're progressing because they sent me some questions about final house as-built locations and grading/survey etc. I had everything they needed so I replied same day. I'm ordering water treatment equipment for the well water today and would like to get some input on CO2 injection for pH control. Seems pretty straight-forward and the only big drawback I can see to traditional acid is the up front expense (~$1500). But This will be a new plaster pool and I remember how much acid addition I required for well over the normal couple of years. My chlorine jug-lugging was wiped out with swg, now I'll be acid jug-lugging! Unless of course I install CO2 injection and have those large CO2 cylinders that are available delivered. Anybody have any first-hand experience with this? Of course I'll have to get Matt the Mad Scientist weigh in @JoyfulNoise.

Chris

View from future driveway location:


Morning view from back of the house standing behind future pool location:


Just after sunset from middle of back porch overlooking future pool spot:

 

[kimkats]

WOWZER! Those views will be SO worth it!!!

I am going to ping @Dirk for the m.a. stuff!

 

[Dirk]

Zero knowledge here about CO2. I use an automated acid injection system with muriatic acid (Pentair's IntellipH). I'll be happy to help you with that if you go down that path.

The only thing I could offer about CO2 is the supply. I store about 6-8 gallons at a time. Five in an outdoor bin, and the rest in the IntellipH tank. I buy it three or four times a year, when it goes on sale. My supplier is around the corner, next to Lowes, which is my second home. So perhaps I have to "replenish" more often than a CO2 tank (just a guess), but it's very convenient to do so (just a stop off on the way to Lowes). Dealing with a big CO2 tank? Lugging it home? Or do they get delivered? Lugging an empty tank back? Finding a place to put it? Dunno. Doesn't sound like less work. But, again, I have no idea how any of that works. Maybe @JoyfulNoise can describe the logistics.

Acid injection works great for my pool. I handle acid just every few months, filling the tank, and IntellipH does the rest. And my pH is dead on every hour of every day. That and a SWG costs me about 10 minutes a week. That works for me! If CO2 is easier than that, go for it!

 

[JoyfulNoise]

The choice between CO2 and muriatic acid is a wash financially. The biggest deciding factor for CO2 is cost and availability. You have to price out CO2 cylinder costs and what the refill prices are. Generally speaking, MA is going to cost less in most areas but not by a whole lot.

That said, CO2 injection is a good way to control pH in your area given the general softness of the water in FL (assuming your well isn’t some crazy cocktail of weird chemicals). The system is simply one of timed injection not unlike @Dirk ‘s IntelliPH setup. You’ll have to fiddle around with the injection time/flow rate a bit at first but once you do, it shouldn’t need much adjustment.

For your plaster startup you’re going to want to use MA because it’s more important to quickly be able to adjust TA as needed. CO2 does not reduce TA at all. So I see CO2 injection as more of a reasonable approach once a pool is in a mature state and you know it’s needs. It may be something you want to rough out now and have all the hook ups for (especially where you’ll keep the cylinders), and then install it after the pool is broken in.

 

[setsailsoon]

The choice between CO2 and muriatic acid is a wash financially. The biggest deciding factor for CO2 is cost and availability. You have to price out CO2 cylinder costs and what the refill prices are. Generally speaking, MA is going to cost less in most areas but not by a whole lot.

That said, CO2 injection is a good way to control pH in your area given the general softness of the water in FL (assuming your well isn’t some crazy cocktail of weird chemicals). The system is simply one of timed injection not unlike @Dirk ‘s IntelliPH setup. You’ll have to fiddle around with the injection time/flow rate a bit at first but once you do, it shouldn’t need much adjustment.

For your plaster startup you’re going to want to use MA because it’s more important to quickly be able to adjust TA as needed. CO2 does not reduce TA at all. So I see CO2 injection as more of a reasonable approach once a pool is in a mature state and you know it’s needs. It may be something you want to rough out now and have all the hook ups for (especially where you’ll keep the cylinders), and then install it after the pool is broken in.

Thanks Matt and Dirk. Very helpful.

Chris

 

[Dirk]

It may be something you want to rough out now and have all the hook ups for (especially where you’ll keep the cylinders), and then install it after the pool is broken in.

Two schools of thought on that. Since it looks like you'll be using MA at first, and maybe more than an automation system could keep up with, the first several months are gunna be manual MA additions. But what about after that? Will your pool continue to require regular pH adjustments, enough to warrant an automation system (like my pool), or will your pH stabilize and require very little adjustment (like Matt's).

Well, you could wait a while, maybe a year, to see what your pool is going to actually need, and then decide at that point what type of pH-adjusting system is best, or if any is needed at all. Typically pH rise gets less over time. Some say it takes about a year. Some pools level out but still have a constant need. Others end up needing very little adjustment after a while (has to do with pool finish "break in" and the chemical make up of the fill water source). So maybe in a year you'll realize that keeping your pH adjusted is a simple matter of a little MA once in a while. And you'd have saved all the initial expense of a system you didn't really need.

Or you could follow my logic, which wasn't really based on anything more than just a hunch. I purchased my IntellipH before I was sure I would need one long term. The logic being: if I'm going to spend the money to automate, why not get the benefit of automation right away, especially when my pool needs a lot of acid. It turned out my pool continued to be rather thirsty for acid (because of my fill water), so the IntellipH was a good investment, and getting it right away paid off. But it was a bit of a roll of the dice.

And lastly, there's another consideration. Water features, like spa spillovers, or laminars, or fire bowls, or sheers or bubblers, etc, all contribute to pH rise, and require something to bring that pH back down. If your pool is going to have some of those types of features, and you think you're going to want to run them a lot, then some sort of pH-reducing automation might be a good idea. But there's a flip side even to that. These water features always sound fantastic in the planning stage, and pool builders like to build 'em, because they have a fantastic profit margin, and you'll turn them all on and be super proud... for about a month. Then the electric bill shows up and you realize they're not all that neat-o and they're kinda noisy, and you just "forget" to use them all that much. After a time you only turn everything on to show off for guests, and that's about it. So the pH system was not really that great of an investment after all...

All stuff that's sort'a hard to predict, but you can ponder it. Or if you've got the patience, waiting to see if automating pH is really going to be necessary is certainly not the worst way to go.

 

[setsailsoon]

Two schools of thought on that. Since it looks like you'll be using MA at first, and maybe more than an automation system could keep up with, the first several months are gunna be manual MA additions. But what about after that? Will your pool continue to require regular pH adjustments, enough to warrant an automation system (like my pool), or will your pH stabilize and require very little adjustment (like Matt's).

Well, you could wait a while, maybe a year, to see what your pool is going to actually need, and then decide at that point what type of pH-adjusting system is best, or if any is needed at all. Typically pH rise gets less over time. Some say it takes about a year. Some pools level out but still have a constant need. Others end up needing very little adjustment after a while (has to do with pool finish "break in" and the chemical make up of the fill water source). So maybe in a year you'll realize that keeping your pH adjusted is a simple matter of a little MA once in a while. And you'd have saved all the initial expense of a system you didn't really need.

Or you could follow my logic, which wasn't really based on anything more than just a hunch. I purchased my IntellipH before I was sure I would need one long term. The logic being: if I'm going to spend the money to automate, why not get the benefit of automation right away, especially when my pool needs a lot of acid. It turned out my pool continued to be rather thirsty for acid (because of my fill water), so the IntellipH was a good investment, and getting it right away paid off. But it was a bit of a roll of the dice.

And lastly, there's another consideration. Water features, like spa spillovers, or laminars, or fire bowls, or sheers or bubblers, etc, all contribute to pH rise, and require something to bring that pH back down. If your pool is going to have some of those types of features, and you think you're going to want to run them a lot, then some sort of pH-reducing automation might be a good idea. But there's a flip side even to that. These water features always sound fantastic in the planning stage, and pool builders like to build 'em, because they have a fantastic profit margin, and you'll turn them all on and be super proud... for about a month. Then the electric bill shows up and you realize they're not all that neat-o and they're kinda noisy, and you just "forget" to use them all that much. After a time you only turn everything on to show off for guests, and that's about it. So the pH system was not really that great of an investment after all...

All stuff that's sort'a hard to predict, but you can ponder it. Or if you've got the patience, waiting to see if automating pH is really going to be necessary is certainly not the worst way to go.

All great points, thank you Dirk. I'm not super patient and I like to tinker with new stuff. So I'm likely to at least experiment just to get started. We don't have a spillover in the spa but I do have an infinity edge with a couple of feet drop to a basin. And the rest of the edges are knife edge so the surface area is a little larger. All of this should translate to more than normal aeration for this size pool. So I'm pretty sure we'll have pH challenges for the first year at least and therefore I am also thinking about base loading with CO2 and just adding acid when needed.

Chris

 

[setsailsoon]

One other thing I will add is about insulation. We are planning to go with the following:

• R-30 open cell foam applied to underside of roof for entire house and R-20 above garages.
• R-9 open cell filled block for the entire block structure. Blocks alone would seem to be good insulated materials but they're not (only about R-2)
• R-5 radiant barrier aluminum film inside house directly applied to the block and furring strips.
• We have impact rated composite windows with e-coating and have omitted the argon-filled insulated window additional pane. The insulated window in our climate with very little winter heat (couple days per year) made almost no difference to our energy modeling. Plus our experience with them is after 7-10 years the start to have problems with the seal causing gas to leak out and condensation in the panels. So I decided to put that money into more efficient ac (SEER 16 or 17).

I was quite surprised the R value of radiant barrier film is about the same as 3/4" urethane foam. This was an easy choice since it also leaves more room to fish between the dry wall and block for future additions.

Thoughts?

Chris

 

[JoyfulNoise]

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