# Kitchen Drywall+Cement Board



## tk3000 (Oct 17, 2015)

At a very slow pace I am redoing a kitchen that have had lots of water damage in the past due to a slow leak in a vacant house. Most of the damaged subfloor was replaced. But, it seems that drywall is very prone to water absorption and mold +*mildew*growth in a naturally humid environment, and often when drywall it is contaminated with mold or mildew it needs to be replaced due to be porous,etc. So I decided to partially use (bottom segments that are more likely to be contaminated) 1/2 cement boards instead of drywall as shown below:* 







Note that the cement board (backerboard) portions will be behind the future kitchen cabinetry, so any potential imperfection or unevenness will not be visible. I am also using some 2x4 blocks to provide extra support for the edges that don't meet at a stud. 

I understand that since I am using*backerboard+ drywall (existing upper portion), where they meet (joint) I should use thinset+tape(forbackerboard) to seal their union. Also, leaving 1/4" gab all the way around. Is this a good approach to this situation? 

thks


----------



## beachguy005 (Oct 18, 2015)

Using durock is a bit overkill. You can use greenboard, which is sheetrock for damp locations.  If you're expecting that much more water that you think you need cement board, you've got bigger issues with leaks.


----------



## KULTULZ (Oct 18, 2015)

Cement board will absorb water (tile grout will pass water).

Green board is not recommended for wet locations any longer (it is just wax coated drywall on the face only) but new products available (fiberglass wall board - even blue board) will prevent minor water damage/mildew.

Of course you have to have no water plumbing leakage and have proper ventilation (bathroom).

Open to correction if I am wrong-


----------



## beachguy005 (Oct 18, 2015)

If it's still a wet location then nothing should be installed there.  It's not a shower, it's behind kitchen base cabinets.  Green board is perfectly fine for using there.


----------



## CallMeVilla (Oct 19, 2015)

Something isn't right in this description.  I am going to guess your kitchen is humid but there are no leaks and no puddles or flowing water present.

Green board is water "resistant" but not water "proof."  If it is subjected to splashed water or puddles at the floor, it can absorb water and fail in 3-8 years.  That is why showers are now built with tile backer which is further coated with rolled on sealant such as RedGard.  The seams are taped and mudded (fiber tape) and also get RedGard sealant.  This approach IS water proof and is used for tiled showers.

I think sheets of tile backer are overkill for your kitchen walls.  Can you do it?  Sure.  Could you also roll sealant on the walls?  Sure.  All of this is expensive.
Do you NEED to do this?  Probably not.  Green board would be adequate  ...  and you can use a RedGard product to ease you rmind before finishing the kitchen.  I would, however, make sure your leave a gap at the floor so leaks would not pile up against the green board.

[ame]https://www.youtube.com/watch?v=mG5GIqcYkSs[/ame]


----------



## beachguy005 (Oct 19, 2015)

The reality is that anything the OP puts on the wall, regardless if it's cement board or greenboard, coated with a waterproofing membrane or not, is not going to prevent any major water damage.  It's a vertical surface, most damage will be to the floor and bottom plates of the wall.  Frankly, I would rather have something behind the cabinets that would be more vulnerable to water damage than something waterproof that would hide any leaks.
Any water leaks in a wall need to be addressed as soon as possible. Trying to use materials that would slow the observation of existing water leak is a mistake.


----------



## KULTULZ (Oct 19, 2015)

What was the source of the original leak, plumbing or roof? Has it been repaired/corrected?

*-DensArmor Plus® Interior Panels-*


----------



## tk3000 (Oct 20, 2015)

KULTULZ said:


> Cement board will absorb water (tile grout will pass water).
> 
> Green board is not recommended for wet locations any longer (it is just wax coated drywall on the face only) but new products available (fiberglass wall board - even blue board) will prevent minor water damage/mildew.
> 
> ...



I understand that cement absorbs water, but it is not a good environment for the growth of mold and it will not be structurally compromised by moisture and in case mold crops up (just scrap it out). Besides is structurally much more sound than drywall. It may not be best the options but it seems much better than drywall.

Confess that I haven't heard about green board or fiberglass board, I should have consult with your guys before buying the cement board.

thnks!


----------



## tk3000 (Oct 20, 2015)

KULTULZ said:


> What was the source of the original leak, plumbing or roof? Has it been repaired/corrected?
> 
> *-DensArmor Plus® Interior Panels-*



It was a small leak related to the the plumbing. The main water supply from the street was supposed to be off, but it seems that the utility worker did not fully closed the water supply valve at the curb and small persisting leaking went unchecked for a long time when the house was vacant.  The leak was fixed a few months ago, so it is all good now. I noticed that the vast majority of the mold was at the lower spots on the drywall.


----------



## tk3000 (Oct 20, 2015)

beachguy005 said:


> Using durock is a bit overkill. You can use greenboard, which is sheetrock for damp locations.  If you're expecting that much more water that you think you need cement board, you've got bigger issues with leaks.



Hmmm... I confess that I haven't heard about the this greeboard thing. I saw backerboard been used quite often in bathroom though. No, I don't expect any water leak any time soon; but it is a kitchen (with lots of appliances that use water: dishwasher, refrigerator, disposable, etc). So, it is more likely to spur the mold growth. I want to create an environment whereas mold will have a hard time settling in. 

I will look into this greenboard thing, but sheetrock is rather weak and any protective coat will hold hold for long.  

thks


----------



## tk3000 (Oct 20, 2015)

CallMeVilla said:


> Something isn't right in this description.  I am going to guess your kitchen is humid but there are no leaks and no puddles or flowing water present.
> 
> Green board is water "resistant" but not water "proof."  If it is subjected to splashed water or puddles at the floor, it can absorb water and fail in 3-8 years.  That is why showers are now built with tile backer which is further coated with rolled on sealant such as RedGard.  The seams are taped and mudded (fiber tape) and also get RedGard sealant.  This approach IS water proof and is used for tiled showers.
> 
> ...



Yep, there is no leak; it has all being fixed few months ago. But I saw so much mold, I decided to use a strong material that is less prone to mold. I am using 1/4 to 1/8 inch clearance all the way around the cement boards (using spacers ). It is a small kitchen area, so it does amount for a large expense. 

I will look further into the Redguard, it seems to be a great product. thks!


----------



## tk3000 (Oct 20, 2015)

beachguy005 said:


> The reality is that anything the OP puts on the wall, regardless if it's cement board or greenboard, coated with a waterproofing membrane or not, is not going to prevent any major water damage.  It's a vertical surface, most damage will be to the floor and bottom plates of the wall.  Frankly, I would rather have something behind the cabinets that would be more vulnerable to water damage than something waterproof that would hide any leaks.
> Any water leaks in a wall need to be addressed as soon as possible. Trying to use materials that would slow the observation of existing water leak is a mistake.



All the water leakage has been addressed a long time ago, so we are ok in this department. 

Yeah, a sealed wall with potential water leakage in the future is something to be avoided. I intend to have opening and small access doors to every and each pluming running inside walls. The point is that the vast majority of the wall does not have pluming or fixtures behind it.


----------



## nealtw (Oct 20, 2015)

Overkill unless you are planning on using tyhe room as a swimming pool too.


----------



## beachguy005 (Oct 20, 2015)

As nealtw pointed it's still overkill.  No one does what you're looking to do.  Every kitchen has water and humidity but they still use regular sheetrock for walls behind cabinets, even walls with plumbing in them.  You didn't have mold because it's a kitchen and it's humid and has plumbing in the walls.  You had mold because you had a water leak that wasn't repaired in a timely manner.
If your leak is repaired and the mold has been killed and cleaned, installing regular sheetrock won't cause more mold.  Conversely, using cement board or anything else won't prevent mold if there is another, or continuing, water leak.


----------



## bud16415 (Oct 21, 2015)

I personally dont see anything wrong with the use of the cement board behind the counters. Yes its overkill but thats the beauty of DIY the material cost is insignificant many times compared to labor so cover it with what makes you feel safe. I would paint it up good before placing the bases. My nephew covered a whole wall with it in his garage as he was putting a wood stove in and he liked the idea of using it as a fire wall. 

If you have the material and you know the leak is fixed go for it.


----------



## beachguy005 (Oct 21, 2015)

You are correct....there is nothing "wrong" with doing it with cement board, or marine grade plywood or galvanized steel for that matter, but there is a difference between doing something correctly and doing something that's not wrong.


----------



## tk3000 (Oct 22, 2015)

beachguy005 said:


> As nealtw pointed it's still overkill.  No one does what you're looking to do.  Every kitchen has water and humidity but they still use regular sheetrock for walls behind cabinets, even walls with plumbing in them.  You didn't have mold because it's a kitchen and it's humid and has plumbing in the walls.  You had mold because you had a water leak that wasn't repaired in a timely manner.
> If your leak is repaired and the mold has been killed and cleaned, installing regular sheetrock won't cause more mold.  Conversely, using cement board or anything else won't prevent mold if there is another, or continuing, water leak.



You have a point though, I probably was severely traumatized for seeing so much nasty concentrated black mold (and even ears shaped mold, arghhh) all at the bottom of the old drywall...

But then drywall is porous powder like material which is not only a good environment for mold grow but it also absorbs and retain water (yeah, cement absorbs water too but it does not retain at the same rate for as long and it dries out rather quick), on top of that there is not reliable way to remove mold from drywall once it settles in.  

Sure enough, in a dry and clean environment mold should not be an issue with drywall; but then why not go to the extra mile and have further protection: cement board is not mold proof, but it much harder for mold to growth there; besides it is a more structurally sound material. Also, right behind the kitchen is the small future laundry room.


----------



## tk3000 (Oct 22, 2015)

beachguy005 said:


> You are correct....there is nothing "wrong" with doing it with cement board, or marine grade plywood or galvanized steel for that matter, but there is a difference between doing something correctly and doing something that's not wrong.



Yep, what is acceptable or not varies a whole lot depending on where you live and what your references are; and so the definition of the best approach or the most cost effective approach, or the proper way, etc.

For instance, I lived in countries whereas houses made out of lumber would would simply be unacceptable; here in the US it is common place.  Among other things, wood is organic matter which is subject to decay, can not stand water, it is fuel for a fire, and a great environment for mold growth, prone to termite destruction, etc...


----------



## nealtw (Oct 22, 2015)

tk3000 said:


> Yep, what is acceptable or not varies a whole lot depending on where you live and what your references are; and so the definition of the best approach or the most cost effective approach, or the proper way, etc.
> 
> For instance, I lived in countries whereas houses made out of lumber would would simply be unacceptable; here in the US it is common place.  Among other things, wood is organic matter which is subject to decay, can not stand water, it is fuel for a fire, and a great environment for mold growth, prone to termite destruction, etc...



I am not sure I agree with saying, there is a proper way, the last time I said that about a different way of doing something, it became code the next year.

We know that wooden structures will stand for hundreds oif years if issues of moisture and venting and insects are dealt with properly and I am not sure that concrete board would make any difference. There is organic fibers in that board, it may not mold as fast but it would just hide a bigger problem for a longer time.
But I still don't think there is anything really wrong with using it if you want to.


----------



## beachguy005 (Oct 22, 2015)

tk3000 said:


> You have a point though, I probably was severely traumatized for seeing so much nasty concentrated black mold (and even ears shaped mold, arghhh) all at the bottom of the old drywall...
> 
> But then drywall is porous powder like material which is not only a good environment for mold grow but it also absorbs and retain water (yeah, cement absorbs water too but it does not retain at the same rate for as long and it dries out rather quick), on top of that there is not reliable way to remove mold from drywall once it settles in.
> 
> Sure enough, in a dry and clean environment mold should not be an issue with drywall; but then why not go to the extra mile and have further protection: cement board is not mold proof, but it much harder for mold to growth there; besides it is a more structurally sound material. Also, right behind the kitchen is the small future laundry room.



  Why not go the extra mile?  Because millions of houses have been built without your extra mile and it shows us that just sheetrock is fine.  If you look at 1000 houses in your area I would be willing to wager that none of them have done what you want to do and that all of them have just sheetrock. Granted you may find some nitwit house flipper, and I'm in no way referring to you, that did it because he had scrap cement board laying around.  The reality is that it's your house and your project, do what you think is best for you.


----------

