Shotcrete versus Gunite

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N

NineAcre

0
Sep 6, 2016
19
Edgartown,MA
We're getting quotes for a new IG pool about 20'x40' and some are proposing shotcrete and others gunite. The shotcrete bids are coming in about $20K higher than the gunite bids. Any opinions on which is "better" or what I should consider?

Thanks!
 
They are basically the same thing. Look it up on Wikipedia. I believe shotcrete is the general name for the process and "gunite" is an actual trademarked name. The only difference in the overall process is if they do the shotcrete wet out of the nozzle or if the do it it dry and mix water in at the nozzle. I believe gunite specifically refers to a dry mix being pneumatically pumped out and mixed with water after the nozzle.

They should produce the same end result and there should be no difference in price. Something sounds fishy.
 
Shotcrete has the advantage of having larger aggregate in the mix and the yields are typically higher in compressive strength given the same precured cement content. Some may also argue that more pneumatical force can be be applied to Shotcrete during application yet still produce minimal rebound.

All things considered in a swimming pool, either option will produce a strong shell. The skill and knowledge of the applicator and crew will far supercede any negligible differences between the two.

If you talk to a gunite guy, he'll say gunite is best. If you talk to a Shotcrete guy, he'll say Shotcrete is best. Truth be told, once set up to do gunite or Shotcrete, a switch to the other would be very expensive and require purchasing new equipment.

I don't see how the bids are 20k higher for Shotcrete. In my experience in my area, gunite is running $10/yard more than Shotcrete right now.
 
In my situation, since I am OB, I chose a company that does both. They guarantee lifetime warrantee on the shell for either product and told me it was my choice, as both are the same PSI strength in the end. I told them they could choose which they would like to use, since both were the same price, and they were the ones warranting the work. They chose Gunite. In talking to the guys that were applying it, they liked gunite a bit more because they felt that they could control the mix better, since it was being done at the nozzle, rather than premixed and shot out.. So, I would ultimately go with the less expensive solution in your case, since the end result is supposed to be the same.
 
That's a strength and weakness for both.

From my perspective, I can order the Shotcrete and specify the cement, aggregate, and water content (slump) which are then measured by a computer and generate a ticket that shows each of those parameters and the batch mix time so I know how long it's been in the truck. Once the truck arrives, I'll look into the barrel and then pour a couple slugs that can later be tested to confirm I got what I paid for. On very hot days, plasticizers can be added to replace/reduce the water needed for application without decreasing the ultimate cured strength.

Gunite is much different. I prefer to have the mix brought dry in a cement truck for the same reasons mentioned above but not all contractors do this. There are a couple contractors near me that dump sand in the street and shuttle it to their equipment with a skip loader where it is then mixed with cement and carried to the nozzle by compressed air. In this scenario the cement/sand ratio is nothing more than an approximate, as is the water/cement ratio as the nozzle applicator controls it basically by sight. The finishers prefer a wetter mix because it's easier to trowel and smooth but this yields a much weaker product that is prone to shrinkage cracks and reduced compressive strength.

I don't want to sound biased in one way or another but my experiences make me lean toward Shotcrete; part of that has to do with very bad experiences with a local ready mix company.

Barring a quality and knowledgeable contractor, either product will be a fine choice.

My pool is Shotcrete and I built my neighbor's with gunite... Both are still holding water
 
I'm going to generally agree with BriAn here. I will add that in Sacramento the gunite generally comes from a national supplier that runs mix trucks and generally delivers a consistent product.

But in the end you end up with results that are indistinguishable.
 
One more interesting thing, you can take it for what its worth. I was talking with my plasterer about the difference, and he stated that he would rather plaster Gunite over Shotcrete. His reasons were (1) the plaster bonds much better to Gunite, in his experience, and (2) He says that generally Gunite is smoother with less bulges, etc. more fodder I guess...lol
 
daddymack said:
One more interesting thing, you can take it for what its worth. I was talking with my plasterer about the difference, and he stated that he would rather plaster Gunite over Shotcrete. His reasons were (1) the plaster bonds much better to Gunite, in his experience, and (2) He says that generally Gunite is smoother with less bulges, etc. more fodder I guess...lol
Click to expand...

If I was a plaster contractor, I'd prefer gunite too. A smoother surface means less plaster material and an easier job.

Shotcrete is very rough compared to gunite. I don't see how any cementious material would bond better to a smoother surface but I guess the contractor's experience will far outweigh mine.
 

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bdavis466 said:
If I was a plaster contractor, I'd prefer gunite too. A smoother surface means less plaster material and an easier job.

Shotcrete is very rough compared to gunite. I don't see how any cementious material would bond better to a smoother surface but I guess the contractor's experience will far outweigh mine.
Click to expand...

The Surface is more even (less bulges, etc). Maybe smoother was a poor choice of words..
 
We had 4 pool bids and one of 4 was a gunite shell. We went with the PB who quoted us shotcrete and yes it was rough but I felt the Pebble finish would adhere better.


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