New Baja shelf in older pool- Question

[Tito1981]

Should I allowing builder to buid my baja shelf in my older pool with rocks placed as fillers. Should I not allow my builder to move forward using that same method or is it okay?

 

[Dirk]

It's actually pretty involved, and not just a matter of filling a space with rocks and covering them with concrete. The new structure (the shelf) has to be tied into the existing structure (the pool) and filled such that it cannot shift. Otherwise the new finish can crack.

Use the TFP search field and look for "add baja shelf" and you'll see lots of threads about it.

Be sure your builder knows what he's doing...

@jimmythegreek, got any advice for Tito?

 

[Tito1981]

My PB is doing a 9'x18' baja on shallow end having 12 " depth. First they are doing a box structure reinforced with some rebar but my concer is that the rebar wouldn't be attached into the pool to "to protect the original pool structure and prevent leaks"
My second concern is that the their perimeter is a wooden plywood drilled to the pool's plaster- would the screws damage the pool's water proof capacity. Or once the screws are removed and pebble tec is sprayed over, it would not be a problem? see attached pictures

 

[Dirk]

Any attachments or holes or rebar or screws that penetrate into the shell will not affect the pool's water-tightness. The gunite shell isn't water proof. Only the finish is (the plaster or pebble). That's why it's important for them to create a strong structural bond between the existing shell and the new shelf structure. I'm not a builder, and I don't know how that's done. I only know that if it's not done correctly and the shelf moves or settles relative to the original shell, the new plaster will crack and that's what will cause a leak.

I think I'm following your logic: that if the original pool finish is not penetrated anywhere, then no matter what the new shelf or its finish does, the water won't get past the "old pool." And that sure sounds reasonable. But I'm not sure it can work that way. They have to somehow attach the new rebar to the old pool, and as soon as they penetrated the old finish with anything to do that with, then the old finish will not be 100% waterproof. I think it's better they attach the new shelf really well, whatever that takes, and then your new finish will take care of waterproofing the pool. Let me try Jimmy again?

@jimmythegreek, which is better: to leave the original finish alone (if that's even possible), or to tie in the new rebar to the existing shell for a strong bond between the two structures?

 

[Dirk]

My second concern is that the their perimeter is a wooden plywood drilled to the pool's plaster- would the screws damage the pool's water proof capacity. Or once the screws are removed and pebble tec is sprayed over, it would not be a problem? see attached pictures

Yes, any small screw holes in the existing plaster would be sealed up well by the new finish. But are they not removing the old plaster? How are they blending the new finish into the old if they're not removing the old?

 

[Tito1981]

Yes, any small screw holes in the existing plaster would be sealed up well by the new finish. But are they not removing the old plaster? How are they blending the new finish into the old if they're not removing the old?

thanks for the information. The PB has removed the old plaster and the pool has been stripped completely.

 

[Tito1981]

Yes, any small screw holes in the existing plaster would be sealed up well by the new finish. But are they not removing the old plaster? How are they blending the new finish into the old if they're not removing the old?

Thanks for the information. The PB has removed the old plaster and the pool has been stripped completely.

 

[jimmythegreek]

To add a shelf a form is made with rebar that is tied with epoxy to the old pool shell. Once cured there should be rebar left sticking up out of the form that is bent over to begin making a grid to tie into the floor of the shelf. Filling the shelf form with angular stone is the proper way and compacted. Then a grid is attached to the rebar stubs bent over and the floor is poured. Finally a new plaster finish is applied. Any holes are filled with plaster that waterproofs the pool. Any larger holes filled with hydraulic cement. Shouldnt really be any large ones anyway

 

[Dirk]

Thanks Jimmy! If I'm understanding that correctly, they'll drill holes into the shell and glue in (with epoxy) rebar shoved into those holes. Plus, Tito, your plaster is already gone. You don't need to worry about holes, large or small, in the shell. As I mentioned, the shell is not watertight anyway. Once they form and shoot the new shelf (which would fill any large holes), they'll give you a nice coat of new finish (filling any remaining smaller holes) and that's what will make your pool waterproof. If they tie the new rebar into the old shell as Jimmy describes, and properly compact the stone he also described, then the new shelf shouldn't shift around any and cause any cracks in the new finish.

Assuming you are being given a warranty for this work, just do the bucket test periodically before the warranty expires, to ensure the new finish is sound. If you get through the first few years OK, that's all you can hope for. This article describes how to do the bucket test:

Leak Detection

A number of things can cause leaks in your pool. You can learn tricks for leak detection and how to pinpoint where your pool is losing water.

www.troublefreepool.com

 

[jimmythegreek]

Well said Dirk, excellent advice

 

[Tito1981]

Thanks Jimmy! If I'm understanding that correctly, they'll drill holes into the shell and glue in (with epoxy) rebar shoved into those holes. Plus, Tito, your plaster is already gone. You don't need to worry about holes, large or small, in the shell. As I mentioned, the shell is not watertight anyway. Once they form and shoot the new shelf (which would fill any large holes), they'll give you a nice coat of new finish (filling any remaining smaller holes) and that's what will make your pool waterproof. If they tie the new rebar into the old shell as Jimmy describes, and properly compact the stone he also described, then the new shelf shouldn't shift around any and cause any cracks in the new finish.

Assuming you are being given a warranty for this work, just do the bucket test periodically before the warranty expires, to ensure the new finish is sound. If you get through the first few years OK, that's all you can hope for. This article describes how to do the bucket test:

Leak Detection

A number of things can cause leaks in your pool. You can learn tricks for leak detection and how to pinpoint where your pool is losing water.

www.troublefreepool.com

Thanks Derik for plugging me with Jimmy. I truly appreciate your advice and it has placed me at ease. The PB is doing all the mentioned procedures.

 

[Dirk]

You were smart to check.