Gunite Pool Resurfacing

[MimiDucky]

We have a medium size (15k gallons) inground gunite pool that was built in 1992, so about 30 years old. Never been resurfaced. The marcite started to show signs of erosion probably 10 years ago but in recent years it’s gotten worse. We now have major discoloration on the steps, bottom and walls, as well as black patches in the bottom (I think it’s the gunite showing through). Anyway, we really need to resurface, and thinking of doing it in the next month or so (before the rainy season). Nothing fancy in this pool - no spa, no sun ledge, no waterfalls, just a standard pool that came with the house when we bought it.

We’re torn on which surface to get. We really like the look of the white marcite, but I’ve read that modern-day plaster doesn’t last very long, so we’re also looking into quartz and pebble but not sure which one to get. Obviously cost is a concern, but apart from that, the look we’re looking for is: white or close to it (no colors or speckled/mottled stuff), smooth (flat/no texture), and matte (no shiny stuff). We’d also like something that lasts a while since we have no plans to move anytime soon. Some options I saw were DiamondBrite (in ‘oyster’), Quartzscapes (in ‘ivory’), PebbleFina (in ‘classico’), and of course plan B - regular white marcite. Any thoughts to help me decide? Are any of these textured and/or really shiny? Do any of them take longer to install? I’m in Florida if that helps, and the waterline tile and deck are good so not going to redo those, which should keep the cost down.

 

[ajw22]

I’ve read that modern-day plaster doesn’t last very long

You think maybe that is from people who want to upsell you a premium finish?

Basic plaster finish will last a long life if properly maintained. Any finish can be killed prematurely if neglected.

 

[MimiDucky]

Well that may very well have something to do with it. I read that asbestos was removed from plaster in the 90s and it made it much less long-lasting. Is there some truth to that?

I'm totally fine with going the plaster route. I think it looks fine, to be honest.

 

[JoyfulNoise]

Look at Hydrazzo … it’s polished plaster with fine aggregates. Very smooth. And comes in lots of colors including whites.

 

[ajw22]

Plaster from the last century is before my time.

Consider that a premium finish that ”may” last longer will cost more. Have you really saved much if you paid more for a longer life? Your cost per year may have no savings.

Get what you want and focus on good maintenanc.

 

[ajw22]

Look at Hydrazzo … it’s polished plaster with fine aggregates. Very smooth. And comes in lots of colors including whites.

I got 17 years from Hydrazoo and only replaced it due to some rusting rebar. It could have gone 25+ years.

Hydrazoo does cost more with an additional day for the polishing.

 

[MAPR-Austin]

I install all of the cement based finishes, from white plaster to exposed aggregate to glass beads/pebble.

We offer the same 5 year labor/materials warranty on all cement finishes. It is my impression that the cement is the weak point of any finish - it will deteriorate eventually. I have seen finishes that still felt smooth after 20 years (meticulously cared for by the owner, chemistry checked daily), and I have seen some that are as rough as coarse sandpaper after a couple of years of abuse.

Plaster is my favorite for the look and finished feel. Exposed aggregate is necessarily rougher from day one, pebble even more so.

The one key thing to consider regardless of what you choose is the preparation method. If you are seeing gunite, then the plaster should probably be removed completely as it is significantly deteriorated. Chipping out is the most common method. I prefer hydroblasting as it will remove 100% of the old plaster and leave you with a clean, rough surface ideal for receiving the new finish.

 

[MimiDucky]

Agreed, I think we're definitely removing all of the plaster down to the gunite. I don't see any way around it, given the age and condition of the pool.

I didn't realize there were multiple way to remove the plaster. Are there other options that the two you listed? So I know what to ask when I get contractors to come in and provide quotes.

 

[kimkats]

I am in the help and support as needed. @JoyfulNoise & @ajw22 have you well taken care of so far!

One thing you can go ahead and do is get a good test kit. That is the foundation of TFP's pool care. Here is a link to the ones we use on our pools:
Test Kits Compared We even have videos on how to do the tests and we can/will walk you through them. It is not hard but can be overwhelming when you first see all of the test bottles and such. I even bought the test kit BEFORE I bought the pool to make sure I COULD do them LOL

Kim

 

[MAPR-Austin]

Agreed, I think we're definitely removing all of the plaster down to the gunite. I don't see any way around it, given the age and condition of the pool.

I didn't realize there were multiple way to remove the plaster. Are there other options that the two you listed? So I know what to ask when I get contractors to come in and provide quotes.

I think chipping it out is the most common. It is not a bad method.

Sandblasting is used occasionally but makes a tremendous mess and sand gets everywhere.

Acid washing and the bond coating is common but probably not a good choice for your pool given the condition of the existing plaster. Cheapest method.

Hydroblasting is more expensive and requires a sizeable investment in equipment, training, and maintenance. It is objectively the best method to prepare for a new surface - but the cost is not always worth it. I believe it is catching on more in Florida but I do not have any companies to recommend offhand.

The most important thing is that all loose or deteriorated plaster be removed. Then the surface should be pressure washed with a minimum 3500 PSI until it is very clean. You want no dust on the surface, no hollow areas, and a rough profile on the pool shell. When you scrape the surface with a screwdriver it should feel hard. If it is soft and you can gouge it easily, more removal is needed.

 

[AQUA~HOLICS]

If you choose a chipping out method the shell should look like this when finished with no patches of plaster to be seen.
Notice their are no deep gouging marks because flat tip chisels were used, so the least amount of Shotcrete was removed with the plaster.

 

[MimiDucky]

I think chipping it out is the most common. It is not a bad method.

Sandblasting is used occasionally but makes a tremendous mess and sand gets everywhere.

Acid washing and the bond coating is common but probably not a good choice for your pool given the condition of the existing plaster. Cheapest method.

Hydroblasting is more expensive and requires a sizeable investment in equipment, training, and maintenance. It is objectively the best method to prepare for a new surface - but the cost is not always worth it. I believe it is catching on more in Florida but I do not have any companies to recommend offhand.

The most important thing is that all loose or deteriorated plaster be removed. Then the surface should be pressure washed with a minimum 3500 PSI until it is very clean. You want no dust on the surface, no hollow areas, and a rough profile on the pool shell. When you scrape the surface with a screwdriver it should feel hard. If it is soft and you can gouge it easily, more removal is needed.

Thanks! That's very helpful.

Quick question - the waterline tile seems to be in great shape. Is there any way to leave it alone? or will it need to be removed when the plaster goes and then redone? If so, will we be able to reuse the same tiles?

 

[MimiDucky]

If you choose a chipping out method the shell should look like this when finished with no patches of plaster to be seen.
Notice their are no deep gouging marks because flat tip chisels were used, so the least amount of Shotcrete was removed with the plaster.

Thank you! This is great, more information will help us when we meet with the contractors. Question, though - when our plaster started going, it exposed a black surface which we assumed was the gunite, but your pic looks rather white. Are we not looking at gunite? I can share a pic if it helps.

 

[AQUA~HOLICS]

Yes a picture will help, the darker color you observed may be due to the Shotcrete being hydrated and will take on a darker color than the picture I provided.
To help answer your other question, the tile does not have to be removed for a new plaster installation if it’s in sound shape.

 

[MAPR-Austin]

Yes, it is very common to keep the old waterline tile. The step tile will need to be replaced unless you find a contractor who can save them - it is doable but a lot of work.

The should undercut and then chip the plaster from under the waterline tile. They will need to be very careful so they don't damage them.

 

[MimiDucky]

Yes, it is very common to keep the old waterline tile. The step tile will need to be replaced unless you find a contractor who can save them - it is doable but a lot of work.

The should undercut and then chip the plaster from under the waterline tile. They will need to be very careful so they don't damage them.

Thanks, that's reassuring. I think we're ok with redoing the step tiles.

 

[MimiDucky]

Yes a picture will help, the darker color you observed may be due to the Shotcrete being hydrated and will take on a darker color than the picture I provided.
To help answer your other question, the tile does not have to be removed for a new plaster installation if it’s in sound shape.

This is how the largest black area looks (there are multiple smaller areas that look just like it).

 

[AQUA~HOLICS]

From the pictures it looks like the Shotcrete is hydrated and taking on that color.

 

[JoyfulNoise]

I would say that there is no remaining plaster there and you’re simply seeing the shotcrete shell. It’s as if the plaster in that area was chemically eroded away. Perhaps previous owners or pool techs were dumping acid or trichlor tablets in that area and allowing it to sit there.

Does your pool seem to leak? Shotcrete is not waterproof, that’s what the plaster surface is for.

 

[MimiDucky]

From the pictures it looks like the Shotcrete is hydrated and taking on that color.

Thanks! So 2 more questions, sorry... is there a difference between Shotcrete and gunite, or is it basically the same thing? And is the hydrated Shotcrete good or bad (or neither)?

I would say that there is no remaining plaster there and you’re simply seeing the shotcrete shell. It’s as if the plaster in that area was chemically eroded away. Perhaps previous owners or pool techs were dumping acid or trichlor tablets in that area and allowing it to sit there.

Does your pool seem to leak? Shotcrete is not waterproof, that’s what the plaster surface is for.

I don't think so, I haven't seen any noticeable difference in the water level.