Seal Thermal Bluestone Coping on SW pool?

saralines

Bronze Supporter
Aug 3, 2020
78
Los Angeles
My bluestone coverlids were finally installed. My PB suggested sealing the thermal bluestone coping and coverlids with a penetrating sealer because I have a saltwater pool. I asked the local supplier store of bluestone coping and they recommended Stainproof 40SK (Dry Treat brand). The PB said okay, yes. The sub who installed the coping/cover lids said he never used that product and uses something else (trying to find out what).
A) Should I have them seal the bluestone coping?
B) Should they use Stainproof 40SK or somwthing else?
C) I also have an irregular bluestone patio that I installed 6 years ago and never sealed, adjacent to the pool. I'm not sure if I should seal that too? It is obviously not thermal, so will it penetrate differently? It isn't supposed to alter color...

Thanks in advance for your advice.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
18,614
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
You should try to see if you can get a sample sealed first and then look it over carefully. Even penetrating sealers can change the color, sheen and wetness look of the stone. Also know that, if you seal it, it will need to be resealed every 18-24 months (typical). Don't believe them when they say it only has to be done once, that's simply not true. Also, how much freeze/thaw cycling do you get where you are .... not much in LA I'mm assuming? The purpose of sealing a stone is to keep it from absorbing water and thus being susceptible to freeze/thaw damage (cracking and spalling) as well as efflorescence (mineral stains caused by the transport of water and minerals through the stone material). Simply washing the deck down with a hose after a lot of splash out will minimize the mineral staining.

Where did this bluestone originate from? It's not a common stone type in California. Was it shipped in from somewhere? Is it just a manufactured stone material? Bluestone is just the common name attributed to several different types of stone materials. If it's a sandstone stone type "bluestone" then sealing it will be a good idea. However , if the bluestone comes from a basalt family of materials (essentially rapidly cool igneous rock), then sealing it is somewhat unnecessary as it will be quite inert.
 

saralines

Bronze Supporter
Aug 3, 2020
78
Los Angeles
You should try to see if you can get a sample sealed first and then look it over carefully. Even penetrating sealers can change the color, sheen and wetness look of the stone. Also know that, if you seal it, it will need to be resealed every 18-24 months (typical). Don't believe them when they say it only has to be done once, that's simply not true. Also, how much freeze/thaw cycling do you get where you are .... not much in LA I'mm assuming? The purpose of sealing a stone is to keep it from absorbing water and thus being susceptible to freeze/thaw damage (cracking and spalling) as well as efflorescence (mineral stains caused by the transport of water and minerals through the stone material). Simply washing the deck down with a hose after a lot of splash out will minimize the mineral staining.

Where did this bluestone originate from? It's not a common stone type in California. Was it shipped in from somewhere? Is it just a manufactured stone material? Bluestone is just the common name attributed to several different types of stone materials. If it's a sandstone stone type "bluestone" then sealing it will be a good idea. However , if the bluestone comes from a basalt family of materials (essentially rapidly cool igneous rock), then sealing it is somewhat unnecessary as it will be quite inert.
Thx. I did a little sample of dry treat and it seemed not to change the color or look at all, although I also tried it on my patio and it did change that (lighten) which was partially in my concern.

No freezing temps here (very rare). Pennsylvania Blue Thermal Bluestone, as far as I know. Patio is PA Blue Bluestone (irregular). So maybe I don't need to seal?
You should try to see if you can get a sample sealed first and then look it over carefully. Even penetrating sealers can change the color, sheen and wetness look of the stone. Also know that, if you seal it, it will need to be resealed every 18-24 months (typical). Don't believe them when they say it only has to be done once, that's simply not true. Also, how much freeze/thaw cycling do you get where you are .... not much in LA I'mm assuming? The purpose of sealing a stone is to keep it from absorbing water and thus being susceptible to freeze/thaw damage (cracking and spalling) as well as efflorescence (mineral stains caused by the transport of water and minerals through the stone material). Simply washing the deck down with a hose after a lot of splash out will minimize the mineral staining.

Where did this bluestone originate from? It's not a common stone type in California. Was it shipped in from somewhere? Is it just a manufactured stone material? Bluestone is just the common name attributed to several different types of stone materials. If it's a sandstone stone type "bluestone" then sealing it will be a good idea. However , if the bluestone comes from a basalt family of materials (essentially rapidly cool igneous rock), then sealing it is somewhat unnecessary as it will be quite inert.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
18,614
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
I think it's up to you in terms of how much difference it will make. Sealing will protect against staining but it does need to be reapplied on a regular basis. DryTreat and DuPont StoneTec are both very well-regarded products for sealing stone. But they do cost quite a bit and so depending on how large your deck is, you could be looking at hundred (or even thousands) of dollars in material costs not to mention the labor in applying it. If it's part of your build now and you can lay out the money for it, then the incremental cost compared to the overall pool project is small. So you can have the builder apply it now and then see how it holds up and if it's really necessary. If you do it once and then never again, the aesthetics of the stone isn't going to suffer for it. You could even do an experiment and ask them to seal most of the deck except for maybe one or two stones off in the corner and then see how they hold up? If there's no difference after a year or two, then you can forgo sealing in the future. If the ones you didn't seal crumble away to dust or look horrible, then you know the sealer is worth it.
 

saralines

Bronze Supporter
Aug 3, 2020
78
Los Angeles
I think it's up to you in terms of how much difference it will make. Sealing will protect against staining but it does need to be reapplied on a regular basis. DryTreat and DuPont StoneTec are both very well-regarded products for sealing stone. But they do cost quite a bit and so depending on how large your deck is, you could be looking at hundred (or even thousands) of dollars in material costs not to mention the labor in applying it. If it's part of your build now and you can lay out the money for it, then the incremental cost compared to the overall pool project is small. So you can have the builder apply it now and then see how it holds up and if it's really necessary. If you do it once and then never again, the aesthetics of the stone isn't going to suffer for it. You could even do an experiment and ask them to seal most of the deck except for maybe one or two stones off in the corner and then see how they hold up? If there's no difference after a year or two, then you can forgo sealing in the future. If the ones you didn't seal crumble away to dust or look horrible, then you know the sealer is worth it.
Thank you. I have a 12'x31' pool with 15" wide coping. No deck. I have an existing patio that is 6 years old adjacent to the short end of the pool that is about 12'x11' basically. I never sealed it, nor my front walkway and patio in the front yard that are all irregular bluestone and have been there for 9+ years. However, I don't know what the pool water will do. Interesting idea about the experiment.
 

bmoreswim

Mod Squad
Gold Supporter
Platinum Supporter
LifeTime Supporter
Jul 16, 2012
7,009
Central MD
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Certainly no need to seal PA bluestone if you don't want to. It holds up quite well. Especially thermal finish. Mine is natural cleft so I've gotten maybe 1 or 2 flakes in 8 years around the entire pool, just due to its nature and the surface being rougher. But no effect at all from saltwater.
 
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jamjam

Well-known member
Jun 25, 2020
668
NY
Pool Size
25000
Surface
Vinyl
Chlorine
Salt Water Generator
I sealed mine with a no sheen penetrating sealer - it didn’t change any color at all and the stone looks exactly as it did before i sealed it
 

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