Finishing Gypsum Walls

[FACTOR]

What is your preferred way to finish gypsum walls - paint, wallpaper, plaster, wood panelling?

[FACTOR]

And why? What are the advantages of your preferred way of finishing gypsum walls?

[IMHO]

I always finish gypsum walls just like you finish cement rendered ones - in whatever material and color the interior decorator chose

[eyecatcher]

Certainly for the first year after plastering you don't want to be putting anything on it other than emulsion otherwise you will get problems with trapped moisture.

After that time the walls will be dry and you should have been able to consider a number of different finishes according to your taste and style.

[FACTOR]

Certainly for the first year after plastering you don't want to be putting anything on it other than emulsion otherwise you will get problems with trapped moisture.

After that time the walls will be dry and you should have been able to consider a number of different finishes according to your taste and style.

Eyecatcher, Thanks for that useful tip.

[Morakot]

Skim rendered.

Because it looks and feels almost like a high-quality plaster and is more durable than just painting.

[eyecatcher]

That's ok if you plan for it at 1st fix stage.

Applying a further coat after door frames and windows fitted is going to cause mega problems with archs and skirts if you have them.

Unless I misinterpreted your "skin rendered"?

[FACTOR]

Skim rendered.

Because it looks and feels almost like a high-quality plaster and is more durable than just painting.

Can you elaborate on "skim rendered"? What does that involve?

Thanks.

[Morakot]

Skim rendered.

Because it looks and feels almost like a high-quality plaster and is more durable than just painting.

Can you elaborate on "skim rendered"? What does that involve?

Thanks.

Well, there are basically two approaches. One (A) is called level 0-5 drywall fishing; the other ( is a plaster approach, which in the UK is called something like 'plastering with a skim float finish'.

A. Level 5 means that you put a thin coat of compound over your wall (usually with a paint roller) and remove the "excess" with a metal float; let it set and add another layer. For lower levels of finishing look here.

B. This is fundamentally different. You are basically plastering: i.e. spreading layers of compound on the wall and than smoothing it with a (sponge) float. What you put on the wall will stay there, as you build up the plaster. The finished product looks and feels (almost) identical to a plastered masonry wall.

Hope this makes sense. Let us know how you get on.

PS: Take a look at my thread on a ceiling conversion. I actually used a mix of these two approaches; probably not advisable...

Edited March 25, 2014 by Morakot

[FACTOR]

Skim rendered.

Because it looks and feels almost like a high-quality plaster and is more durable than just painting.

Can you elaborate on "skim rendered"? What does that involve?

Thanks.

Well, there are basically two approaches. One (A) is called level 0-5 drywall fishing; the other ( is a plaster approach, which in the UK is called something like 'plastering with a skim float finish'.

A. Level 5 means that you put a thin coat of compound over your wall (usually with a paint roller) and remove the "excess" with a metal float; let it set and add another layer. For lower levels of finishing look here.

B. This is fundamentally different. You are basically plastering: i.e. spreading layers of compound on the wall and than smoothing it with a (sponge) float. What you put on the wall will stay there, as you build up the plaster. The finished product looks and feels (almost) identical to a plastered masonry wall.

Hope this makes sense. Let us know how you get on.

PS: Take a look at my thread on a ceiling conversion. I actually used a mix of these two approaches; probably not advisable...

Now that's what I call an elaborate answer. Morakot, thanks. You just answered a lot of my questions.

Thanks.

[krisb]

Certainly for the first year after plastering you don't want to be putting anything on it other than emulsion otherwise you will get problems with trapped moisture.

After that time the walls will be dry and you should have been able to consider a number of different finishes according to your taste and style.

A whole year?...not true unless you're talikng about masonary walls?. Usually after the gyprock flushing is sanded, that's ready for any finish you want.walls breathe on both sides for a start. 20 something years of being a wall and ceiling tradesman is my backup, I work with the stuff everyday.

Level 5 finish is used to take the flush lines out for painting. You know when you can see where the plasterer has been sometimes when the sun hits the ceiling and walls at certain times of the day? You use a final or top coat and water it down like paint and roll it on, then just sand each layer back, couple layers is enough and it's not even paper thin the finish. It's not used to make the board thicker, for this use a thicker sheet of Gyprock, usually 10mm,13mm and 16mm are the standard sizes. 13mm is good, only 3 mm thicker, but you would break your hand if you hit it. Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock. Solid plasterers usually work on masonary walls.

I think using a good quality paint sealer, then a light sand back of that to take roll marks out, then 2 good coats of quality paint look great. If it's a fancy room,with high ceilings, a nice fancy cornice with a picture rail looks good. Each to their own though.

Edited March 25, 2014 by krisb

[Morakot]

Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock.

This is fairly common in the UK. If you use the so-called 'blue board' (a gypsum board with paper that has high absorbance) than it's as "easy" as plastering a masonry wall.

Edited March 26, 2014 by Morakot

[eyecatcher]

Yes I was thinking hardwall plaster to 16mm thick and in a cooler climate as well.

And of course a 3mm skin coat on board will dry out in no time here.

Thank you for highlighting the difference.

[krisb]

Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock.

This is fairly common in the UK. If you use the so-called 'blue board' (a gypsum board with paper that has high absorbance) than it's as "easy" as plastering a masonry wall.

Blue board as it's known in Australia is used in wet areas. Is that pic taken in a wet area? just looking at the amount of screws used is bit of a giveaway, could be wrong.

Not sure why it would be high absorbant. end of the day it's really just paper with gypsum in between which is already very absorbant.

In the UK, from what I've seen, there isn't much gyprock getting flushed, it's all about plastering the whole wall with a thick coat of plaster.

[sirineou]

Certainly for the first year after plastering you don't want to be putting anything on it other than emulsion otherwise you will get problems with trapped moisture.

After that time the walls will be dry and you should have been able to consider a number of different finishes according to your taste and style.

A whole year?...not true unless you're talikng about masonary walls?. Usually after the gyprock flushing is sanded, that's ready for any finish you want.walls breathe on both sides for a start. 20 something years of being a wall and ceiling tradesman is my backup, I work with the stuff everyday.

Level 5 finish is used to take the flush lines out for painting. You know when you can see where the plasterer has been sometimes when the sun hits the ceiling and walls at certain times of the day? You use a final or top coat and water it down like paint and roll it on, then just sand each layer back, couple layers is enough and it's not even paper thin the finish. It's not used to make the board thicker, for this use a thicker sheet of Gyprock, usually 10mm,13mm and 16mm are the standard sizes. 13mm is good, only 3 mm thicker, but you would break your hand if you hit it. Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock. Solid plasterers usually work on masonary walls.

I think using a good quality paint sealer, then a light sand back of that to take roll marks out, then 2 good coats of quality paint look great. If it's a fancy room,with high ceilings, a nice fancy cornice with a picture rail looks good. Each to their own though.

I was told not to use gypsum board (drywall) for walls in Thailand because of the humid climate, and that you might have mold,

what's your opinion on that?

[chiang mai]

Why not instal a vapor barrier between the drywall and the outer surface, if installed properly it removes all the problems discussed thus far, a tightly sealed sheet of plastic does the trick!.

[FACTOR]

I'm using something called Gyproc Thermaline -- standard gypsum board with a super hard foam insulation backing, total 44 mm thickness. My exterior walls are natural wood.

See the attached file if you want to.

Thanks for all the advice about finishing the gypsum surface.

Gyproc ThermaLine Eng by Thailand Oct 2011_Final Print 2.pdf

[casualbiker]

I'm using something called Gyproc Thermaline -- standard gypsum board with a super hard foam insulation backing, total 44 mm thickness. My exterior walls are natural wood.

See the attached file if you want to.

Thanks for all the advice about finishing the gypsum surface.

you got that here in thailand? How much, where?

thanks Allan

[FACTOR]

I'm using something called Gyproc Thermaline -- standard gypsum board with a super hard foam insulation backing, total 44 mm thickness. My exterior walls are natural wood.

See the attached file if you want to.

Thanks for all the advice about finishing the gypsum surface.

you got that here in thailand? How much, where?

thanks Allan

Actually I got it in a neighbouring country at the local Gyproc Saint Gobain distributor. If you look at the very bottom of the brochure I attached in my previous post, you will see the contact information for Gyproc Saint Gobain in Bangkok and I'm sure they can point you to a local distributor in your area.

[krisb]

Certainly for the first year after plastering you don't want to be putting anything on it other than emulsion otherwise you will get problems with trapped moisture.

After that time the walls will be dry and you should have been able to consider a number of different finishes according to your taste and style.

A whole year?...not true unless you're talikng about masonary walls?. Usually after the gyprock flushing is sanded, that's ready for any finish you want.walls breathe on both sides for a start. 20 something years of being a wall and ceiling tradesman is my backup, I work with the stuff everyday.

Level 5 finish is used to take the flush lines out for painting. You know when you can see where the plasterer has been sometimes when the sun hits the ceiling and walls at certain times of the day? You use a final or top coat and water it down like paint and roll it on, then just sand each layer back, couple layers is enough and it's not even paper thin the finish. It's not used to make the board thicker, for this use a thicker sheet of Gyprock, usually 10mm,13mm and 16mm are the standard sizes. 13mm is good, only 3 mm thicker, but you would break your hand if you hit it. Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock. Solid plasterers usually work on masonary walls.

I think using a good quality paint sealer, then a light sand back of that to take roll marks out, then 2 good coats of quality paint look great. If it's a fancy room,with high ceilings, a nice fancy cornice with a picture rail looks good. Each to their own though.

I was told not to use gypsum board (drywall) for walls in Thailand because of the humid climate, and that you might have mold,

what's your opinion on that?

True. Northern parts of Australia get very humid, same as Thailand. Eventually humidity will find it's way in. It will take a while, and if you use ceiling fans this will help. There are options like solid brick walls, fibre cement sheets, but your ceilings are likely gyprock anyway. Allowing ventilation in the roof space and wall cavity is all you can really do.

[IMHO]

Certainly for the first year after plastering you don't want to be putting anything on it other than emulsion otherwise you will get problems with trapped moisture.

After that time the walls will be dry and you should have been able to consider a number of different finishes according to your taste and style.

A whole year?...not true unless you're talikng about masonary walls?. Usually after the gyprock flushing is sanded, that's ready for any finish you want.walls breathe on both sides for a start. 20 something years of being a wall and ceiling tradesman is my backup, I work with the stuff everyday.

Level 5 finish is used to take the flush lines out for painting. You know when you can see where the plasterer has been sometimes when the sun hits the ceiling and walls at certain times of the day? You use a final or top coat and water it down like paint and roll it on, then just sand each layer back, couple layers is enough and it's not even paper thin the finish. It's not used to make the board thicker, for this use a thicker sheet of Gyprock, usually 10mm,13mm and 16mm are the standard sizes. 13mm is good, only 3 mm thicker, but you would break your hand if you hit it. Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock. Solid plasterers usually work on masonary walls.

I think using a good quality paint sealer, then a light sand back of that to take roll marks out, then 2 good coats of quality paint look great. If it's a fancy room,with high ceilings, a nice fancy cornice with a picture rail looks good. Each to their own though.

I was told not to use gypsum board (drywall) for walls in Thailand because of the humid climate, and that you might have mold,

what's your opinion on that?

How does this 'advice' translate to ceilings, which use the exact same gypsum board?

[Morakot]

Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock.

This is fairly common in the UK. If you use the so-called 'blue board' (a gypsum board with paper that has high absorbance) than it's as "easy" as plastering a masonry wall.

Blue board as it's known in Australia is used in wet areas. Is that pic taken in a wet area? just looking at the amount of screws used is bit of a giveaway, could be wrong.

Not sure why it would be high absorbant. end of the day it's really just paper with gypsum in between which is already very absorbant.

In the UK, from what I've seen, there isn't much gyprock getting flushed, it's all about plastering the whole wall with a thick coat of plaster.

In some places the board for wet areas is called green board. The picture is from someone's blog and I don't think it's a wet area. What I wanted to show is that the boards don't necessarily look blue. I think the paper is actually just thicker.

You might actually know more about this than I do; I think the higher absorbance level has something to do with the type of compound. Apparently the compound for a traditional plaster requires a higher absorbance level than a gypsum based compound that is thinly flushed on the board. With the traditional plaster the moisture is gradually released as the "mud" tries, whereas gypsum based compound will bind a lot of water chemically somehow.

Edited March 27, 2014 by Morakot

[sirineou]

Certainly for the first year after plastering you don't want to be putting anything on it other than emulsion otherwise you will get problems with trapped moisture.

After that time the walls will be dry and you should have been able to consider a number of different finishes according to your taste and style.

A whole year?...not true unless you're talikng about masonary walls?. Usually after the gyprock flushing is sanded, that's ready for any finish you want.walls breathe on both sides for a start. 20 something years of being a wall and ceiling tradesman is my backup, I work with the stuff everyday.

Level 5 finish is used to take the flush lines out for painting. You know when you can see where the plasterer has been sometimes when the sun hits the ceiling and walls at certain times of the day? You use a final or top coat and water it down like paint and roll it on, then just sand each layer back, couple layers is enough and it's not even paper thin the finish. It's not used to make the board thicker, for this use a thicker sheet of Gyprock, usually 10mm,13mm and 16mm are the standard sizes. 13mm is good, only 3 mm thicker, but you would break your hand if you hit it. Building plaster up a few mm is not easy. A solid plasterer could do it, I've never seen it done this way on Gyprock. Solid plasterers usually work on masonary walls.

I think using a good quality paint sealer, then a light sand back of that to take roll marks out, then 2 good coats of quality paint look great. If it's a fancy room,with high ceilings, a nice fancy cornice with a picture rail looks good. Each to their own though.

I was told not to use gypsum board (drywall) for walls in Thailand because of the humid climate, and that you might have mold,

what's your opinion on that?

How does this 'advice' translate to ceilings, which use the exact same gypsum board?

I don't have an opinion in the subject , as I have no experience, with it in Thailand, that's why I ask.

I have extensive drywall systems,experience in the west, (I work in the High rise construction industry)and would love to be able to use the metal stud/drywall system for some partition walls

I have an interior drywall system in Florida USA where the climate is similar to Thailand, but the house has central a/c. In Floridan when I am not there, I am told to run the a/c at a high temperature setting, I set it at 85F to lower the humidity inside, and prevent the house from getting moldy.

When I asked the same question you asked from others

"How does this 'advice' translate to ceilings, which use the exact same gypsum board? "

I was told that the ceilings in Thailand are kept dry by the high temperature in the attic space.

I don't know how much any of this things are true, does anyone have drywall interior walls that are not air-conditioned all the time,and what is their experience pertaining to the mold issue?

As far as finishing it, as others have already said, a blue moisture resistance board for wet areas, regular, probably mold resistant board for the rest of the house, Tape and joint compound for the seams and inside corners, corner bead and joint compound for outside corners.

An oil base primer sealer to seal the compound and paper, and then paint. After that it is up tp your decorating sensibilities. The options range from, wall paper to paneling to paint or even Faux painting.

Edited March 27, 2014 by sirineou

[wpcoe]

Great information. I'm in Mexico now for six months, and may end up buying a house here. I had inquired on a local expat message board here and asked why they don't use a layer of fiberglass beneath the ultra-high (12' to 13' high) ceilings with a simple gyspum/wallboard ceiling beneath them and was told that gyspum wouldn't work because of the high humidity. I didn't understand, but see the same kind of warning in this thread. What would happen to a gypsum ceiling with fiberglass insulation above it? Does the humidity eat away at the gypsum and it crumbles? Does the paper disintegrate? Or, what? Would a water-sealant applied before the pain help?

[sirineou]

Great information. I'm in Mexico now for six months, and may end up buying a house here. I had inquired on a local expat message board here and asked why they don't use a layer of fiberglass beneath the ultra-high (12' to 13' high) ceilings with a simple gyspum/wallboard ceiling beneath them and was told that gyspum wouldn't work because of the high humidity. I didn't understand, but see the same kind of warning in this thread. What would happen to a gypsum ceiling with fiberglass insulation above it? Does the humidity eat away at the gypsum and it crumbles? Does the paper disintegrate? Or, what? Would a water-sealant applied before the pain help?

If I understand correctly, you are asking about Gypsum (drywall) on the ceiling, and fiberglass insulation over it to insulate the ceiling from the attic heat??

Most suspended ceilings are made this way here in Thailand. They frame the ceiling with metal strips, insulate with fiberglass insulation over the metal strips, then they attach drywall underneath the metal strips, tape and plaster normally as in the west.

For ceilings it does not seem to be a problem. I was told because the heat from the attic keep the Gypsum dry.

But I was warned not to use it in the walls, because the lack of circulation and high humidity, could cause mold . I don't know how true that is, I have not tried it my self.

I am just as interested as you to find out as I like working with drywall.

Perhaps some one who has used Gypsum on the wall, and have had it for a while, could chime in and tell as what his/hers experience is.

[IMHO]

All I can say is that we routinely use gypsum with metal studs to create partitions, finish under/around u-shaped stairs, 'delete posts', create decorative features etc, and we have never had any of the problems suggested in this thread. We don't use it for whole walls as it doesn't insulate against sound very well, but I can't see any reason why you couldn't - so long as the people in the next room don't snore too much

If your house is so hot and humid that gypsum could rot or fail, you have much, much bigger problems to face

If you're still not convinced, just use the green bathroom gypsum for your walls

Edited March 31, 2014 by IMHO

[wpcoe]

Great information. I'm in Mexico now for six months, and may end up buying a house here. I had inquired on a local expat message board here and asked why they don't use a layer of fiberglass beneath the ultra-high (12' to 13' high) ceilings with a simple gyspum/wallboard ceiling beneath them and was told that gyspum wouldn't work because of the high humidity. I didn't understand, but see the same kind of warning in this thread. What would happen to a gypsum ceiling with fiberglass insulation above it? Does the humidity eat away at the gypsum and it crumbles? Does the paper disintegrate? Or, what? Would a water-sealant applied before the pain help?

If I understand correctly, you are asking about Gypsum (drywall) on the ceiling, and fiberglass insulation over it to insulate the ceiling from the attic heat??

Most suspended ceilings are made this way here in Thailand. They frame the ceiling with metal strips, insulate with fiberglass insulation over the metal strips, then they attach drywall underneath the metal strips, tape and plaster normally as in the west.

For ceilings it does not seem to be a problem. I was told because the heat from the attic keep the Gypsum dry.

But I was warned not to use it in the walls, because the lack of circulation and high humidity, could cause mold . I don't know how true that is, I have not tried it my self.

I am just as interested as you to find out as I like working with drywall.

Perhaps some one who has used Gypsum on the wall, and have had it for a while, could chime in and tell as what his/hers experience is.

Yes, that's the scenario I was considering: Gypsum/drywall facing the room with a layer of fiber insulation above that. I'm confused on the idea that "heat from the attic keep the Gypsum dry" -- if the insulation was adequate, would the heat not be reaching the gypsum? I don't think fiber insluation would wick moisture away from the gypsum, would it?

In the old world in the old days when I grew up, gypsum was simply screwed to wooden beams (2x4's or 2x6's?) and the fiberglass insulation rolled between the wood beams. It got pretty hot & humid during the summers and that system seemed to work pretty well, but I was clearly told it was not a valid option for the humid Mexican weather which is pretty much the same as humid Thailand weather, I think.

Edited April 5, 2014 by wpcoe

[bbradsby]

For an insulated assembly - ceiling or wall - gyp board is fine in a wet tropical climate. If you get mold-resistant gyp, all the better. For framed walls, this is common knowledge. However, local custom for walls is uninsulated blockwork, and there's the rub if you cover it with gyp - the water vapor will migrate (a good thing, as you dont want to trap it with a plastic barrier) but then get condensed on the concealed, inside surface of the block where the temperature meets the dew point - think about the outside of a glass of beer on a hot day in Samui. If you cover this surface with gyp board you will trap that condensation and mold will be happy to move in, eat the paper off the gyp and drink your dew.

If you use blockwork w/ gyp. board, use AAC block, insulate the inside face of block with 50mm rigid polystyrene, then install gyp on metal Hat Channels screwed through the insulation into the AAC; or for a cheaper solution use AAC block, render it, and work to keep it in the shade from 10:00AM to 5:00PM. Anything you can't shade, paint with radiant reflective paint. GIYF for all these terms/materials.

[bbradsby]

Great information. I'm in Mexico now for six months, and may end up buying a house here. I had inquired on a local expat message board here and asked why they don't use a layer of fiberglass beneath the ultra-high (12' to 13' high) ceilings with a simple gyspum/wallboard ceiling beneath them and was told that gyspum wouldn't work because of the high humidity. I didn't understand, but see the same kind of warning in this thread. What would happen to a gypsum ceiling with fiberglass insulation above it? Does the humidity eat away at the gypsum and it crumbles? Does the paper disintegrate? Or, what? Would a water-sealant applied before the pain help?

If I understand correctly, you are asking about Gypsum (drywall) on the ceiling, and fiberglass insulation over it to insulate the ceiling from the attic heat??

Most suspended ceilings are made this way here in Thailand. They frame the ceiling with metal strips, insulate with fiberglass insulation over the metal strips, then they attach drywall underneath the metal strips, tape and plaster normally as in the west.

For ceilings it does not seem to be a problem. I was told because the heat from the attic keep the Gypsum dry.

But I was warned not to use it in the walls, because the lack of circulation and high humidity, could cause mold . I don't know how true that is, I have not tried it my self.

I am just as interested as you to find out as I like working with drywall.

Perhaps some one who has used Gypsum on the wall, and have had it for a while, could chime in and tell as what his/hers experience is.

Yes, that's the scenario I was considering: Gypsum/drywall facing the room with a layer of fiber insulation above that. I'm confused on the idea that "heat from the attic keep the Gypsum dry" -- if the insulation was adequate, would the heat not be reaching the gypsum? I don't think fiber insluation would wick moisture away from the gypsum, would it?

In the old world in the old days when I grew up, gypsum was simply screwed to wooden beams (2x4's or 2x6's?) and the fiberglass insulation rolled between the wood beams. It got pretty hot & humid during the summers and that system seemed to work pretty well, but I was clearly told it was not a valid option for the humid Mexican weather which is pretty much the same as humid Thailand weather, I think.

Theyre blowing hot air up your serape.

Hot air holds moisture just fine, hot attics dont dry out insulated ceilings, and insulated gyp ceilings are mandatory in hot climates, whether humid or arid. the vapor pressure pushes the water molecules through your building assembly via osmosis and air pressure differential. Thats ok, but you do want to stop air infiltration.

[sirineou]

Great information. I'm in Mexico now for six months, and may end up buying a house here. I had inquired on a local expat message board here and asked why they don't use a layer of fiberglass beneath the ultra-high (12' to 13' high) ceilings with a simple gyspum/wallboard ceiling beneath them and was told that gyspum wouldn't work because of the high humidity. I didn't understand, but see the same kind of warning in this thread. What would happen to a gypsum ceiling with fiberglass insulation above it? Does the humidity eat away at the gypsum and it crumbles? Does the paper disintegrate? Or, what? Would a water-sealant applied before the pain help?

If I understand correctly, you are asking about Gypsum (drywall) on the ceiling, and fiberglass insulation over it to insulate the ceiling from the attic heat??

Most suspended ceilings are made this way here in Thailand. They frame the ceiling with metal strips, insulate with fiberglass insulation over the metal strips, then they attach drywall underneath the metal strips, tape and plaster normally as in the west.

For ceilings it does not seem to be a problem. I was told because the heat from the attic keep the Gypsum dry.

But I was warned not to use it in the walls, because the lack of circulation and high humidity, could cause mold . I don't know how true that is, I have not tried it my self.

I am just as interested as you to find out as I like working with drywall.

Perhaps some one who has used Gypsum on the wall, and have had it for a while, could chime in and tell as what his/hers experience is.

Yes, that's the scenario I was considering: Gypsum/drywall facing the room with a layer of fiber insulation above that. I'm confused on the idea that "heat from the attic keep the Gypsum dry" -- if the insulation was adequate, would the heat not be reaching the gypsum? I don't think fiber insluation would wick moisture away from the gypsum, would it?

In the old world in the old days when I grew up, gypsum was simply screwed to wooden beams (2x4's or 2x6's?) and the fiberglass insulation rolled between the wood beams. It got pretty hot & humid during the summers and that system seemed to work pretty well, but I was clearly told it was not a valid option for the humid Mexican weather which is pretty much the same as humid Thailand weather, I think.

Theyre blowing hot air up your serape.

Hot air holds moisture just fine, hot attics dont dry out insulated ceilings, and insulated gyp ceilings are mandatory in hot climates, whether humid or arid. the vapor pressure pushes the water molecules through your building assembly via osmosis and air pressure differential. Thats ok, but you do want to stop air infiltration.

So then, why is it Ok to use drywall on the ceilings in Thailand, but not the walls?