Baja/Sunshelf Structural Question and pricing

martakeithSeptember 13, 2010

hi, we're in the process of getting quotes for our 18' x 36' freeform pool. We've asked each PB to include a quote for a baja or sunshelf. 2 of the pool builders have referenced reinforcing the shelf with additional gravel and steel (and the costs associated with that), the other pool builder said that there's no need for gravel b/c it is basically just a lump of gunite, shaped accordingly. Has anyone run into this issue before? Or, for any pool builders who might be reading, can you help shed some light on this? We're getting quotes for 5x5 or 4.5 x 6' areas. Thanks in advance!

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I can't say much for the technical side (although they just excavated less near ours), but I can tell you that at day of gunite, there was no questions or talk about price when we changed things around even though it ended up being way bigger then we planned. I don't think it really costs them much more, honestly...But I am saying this as a person having a pool built, not a pool builder.

    Bookmark   September 13, 2010 at 5:38PM
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Your structural question requires more information. Since most PB's send their sales agents out to design and bid on projects they generally have limited expertise. APSP recommends that site specific structural and geotechnical engineering be utilized in the construction of any inground concrete swimming pool. Most high-end builders retain this type of expertise. However, I will do my best to address this for you; If the pool is closer than 5ft. from the foundation of your home additional reinforcing steel will be needed to offset the surcharging forces on the pool beam from your home. Upon excavation the pool floor should be compacted with a sheeps foot roller to a min. 95%. Additional reinforcing double matte steel should be considered at the baja shelf especially when using gunite dry mix given low PSI at 28 days and the leaky nature of gunite. Consider using #4 rebar throughout and in areas where highly expansive soils exist use Dbl Matte #4 with 12" O.C. and stirrups 18" O.C. You may consider using high end additives in the concrete like Aquron 300 and Concrete Pool Shell Protection. I'm just touching this subject, theres much more to building high-end pools than meets the eye.

    Bookmark   September 13, 2010 at 7:15PM
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Although I in most part agree with diypoolpro. The only thing that I would add. Is that in different parts of the country do to soil conditions and your rebar being (#4) 1/2" steel. Here in the southern portion of Texas where there is clay and in does move quite a bit. I recommend 8" O.C and if I am within 5' of the house then I would go 6" O.C with your steel. This being said I would check with your local codes to see what is the recommended placement of you rebar. Most likely the builder you have chosen will know what the standard is, especially if he or she has built pools in the area for a while.

With all this there still may be variables that dictate how this pool is being built.

Good luck on the build.


    Bookmark   September 14, 2010 at 9:03AM
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thank you for the insight. we're in the Boston area, and I have heard from a neighbor who built a pool that our soil has a lot of clay in it. I think our code requires the pool be 10' from our foundation. Not sure of the size of rebar. I'll ask for more details. Any one else have any experience with this? Thanks!

    Bookmark   September 14, 2010 at 9:27AM
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pooltile cleaner,
Welcome to the board, I'm certain your link would be of some value to the OP if the question was about how to properly address mineral buildup on the waterline. But with the topic being sunshelves it came across to me as SPAM.
However the info in your paragraph was good info for the OP.
I had been on this board as Huskyrider for a long time before they booted me off for having my E-mail address visible on a reply. They allowed me back on again under my new name.
I'd hate to see the same happen to you. There's no doubt in my mind that you have a lot to offer the membership with your insight.

I always charge extra for a sunshelf or baja ledge.
The extra costs come from the excavator who must sculpt the sunshelf as he digs, the steel man who places rebar on the rise and tread of the shelf, the guniter who shoots and trims the concrete, and the plaster guy who plasters it.
A shelf of your size costs me about 400+- additional on my construction costs and resells to the customer for 500.
For a buyer I'd call them a must have item on a new concrete pool.
DIYpoolpro is correct about the importance of the steel reinforcement, especially in expansive soil like Fighting Irish described. On the additives he described my preference is fiberglass mixed into the matrix.

Congrats on the new pool!!!

See ya,

    Bookmark   September 16, 2010 at 2:32PM
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Thanks so much to you both, and especially Kelly as it's always helpful to understand the real costs associated with an upgrade! The prices I've been quoted are $2100 and $3500 so I think there might be room for negotiation here.

    Bookmark   September 17, 2010 at 1:45PM
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Kelly is absolutely correct on the pricing on the baja shelf this is the exact same price I quote on them. The only thing that I can think of that might even come close to adding the kind of pricing upgrade your builders have asked for is if you have bubblers and they are on their own seperate pump. the plumbing should run you may $200 to $400 additional and an addition pump if needed $400 to $600 addtional. All depending on how long the plumbing run is and the accual size of pump used.

Good luck,


    Bookmark   September 17, 2010 at 4:15PM
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Another reason for a higher price would be that the excavator didn't sculpt the dirt as he was digging.
If the guniter must build up a sunshelf of your size from the floor to 9" below the beam this could easily gobble up 3 or 4 yards of gunite.
Gunite by the yard, installed and trimmed ain't cheap anywhere!!!
And 3 or 4 yards of gunite in the Boston area could easily hit 800 at cost. If it happened to me in this manner it would cost an easy 500 just for the gunite alone before the other tradesmans cost were added to it.
When a customer hits me with this change after digging I'll shoot the floor, use CMU blocks to build up the shelf, and tie some steel into the beam across the tread down the rise and into the floor. It's a helluva lot cheaper than the monolithic "lump of gunite" your man described. My guess would be that he's not a hands on working pool company owner, but rather he's a point and click owner.
I prefer to sweat a little myself to build something more affordably than to point to the guniter, have him shoot it completely monolithic, and then click the ballpoint pen and write a check for much more than the true value of what it would have cost to do it the correct way to begin with.

See ya,

    Bookmark   September 17, 2010 at 4:59PM
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Thank you so much for the great feedback! We still haven't decided on a PB but when we do I'll be sure to discuss sculpting the dirt with them. Great tip, thanks again! Marta

    Bookmark   September 22, 2010 at 9:41AM
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