Using drywall for outdoor balcony walls.

I've been asked by a client to install drywall alongside his unfinished balcony and paint it all white.

I've never done that kind of work so I asked a Home Depot employee and he recommended Ultralight Mold Resistant "green board". I was a bit skeptical because nowhere does it say "waterproof" on the label so I double checked if it could be used outdoors with possible direct water contact. He said yes. Now I'm reading that it's for indoor use only and that it's only meant for indirect water contact. I've already cut up the board to fit into my car and everything. Can I just use that and put like three coats of outdoor paint, or should I try to return it, but then what should I get instead?

I know there are special boards like Fiberock Aqua Tough but they're meant as backing for tiles and not to be direclty exposed. What he wants is just white paint, is there any way I can achieve something like that using some specialized board? Another thing is that I got regular steel screws, but I'm reading that they can rust, so what should I be using to fasten the boards? Thanks.

 

Drywall does not belong outside. Period.

What he needs is a smooth trowelled stucco.

 

But it will be under a roof, so I don't expect it be wet constantly, only just from occasional stray droplets, so you think a decent of coat of paint won't work? edit: and can you suggest any other approach less complicated than stucco? Like maybe cement board or something?

 

Sheetrock cannot be installed outside in any condition or location. Just the moisture outside would ruin it.

Cement board would work if that gives you the required finish. It's somewhat of a rough finish.

 

Can I just paint it? Or do I need to apply something else to it to make it water resistant?

 

Cement is already water resistant. I would use a porch and floor enamel to paint it.

There may be other paint choices that I am unaware of.

 

Allright, thanks. What if use something like quick set mortar to apply a light coat to the cement board to fill in the rought spots? Then paint it? Would that give it a smooth look?

 

Skim coating the cement board with a setting compound would be a good way to get a smooth finish and would be fairly water resistant.

With drywall it wouldn't be a long term wall covering! Priming and then painting with a latex enamel [any sheen] would help but sooner or later the moisture/humidity would get to it.

 

I will probably go with that method then. I'll see if I can return the sawed-in-half drywall boards back considering it's the employees fault for recommending them in the first place. Thanks to those that helped.

 

Good luck on returning the drywall, generally they won't refund on drywall that's been cut but since they recommended it for an exterior application ..... maybe if nothing else they'll give you a good discount on the cement board and setting compound.

 

You don't normally saw drywall sheets. You score with a utility knife on the front side, snap, and cut the paper on the back with a utility knife.

Mark, I thought they were talking about T-111 cement board. Does setting compound mean we're talking about backer board?

 

I was assuming the 3'x5' cement boards and finishing them to look more like drywall.
Maybe Tim should clarify

 

@ray yea I just scored it with a knife and snapped it since it wouldn't fit in my car.

I really don't know what kind of boards to use, that's why I'm here. Aren't all cement boards the same? If not which one should I get and which compound should I get to make it as smooth as possible? If possible please use a proper name for the board instead of like 3x5 or 'that green one' so I can get the exact product.

 

Cement board which is a tile backer comes in 3'x5' sheets, either 1/4" or 1/2" thick. The 2 most common brands is hardibacker and wonder board. There are also cement siding which comes both as traditional lap siding and 4'x8' sheets. I'm not aware of any sheets of cement siding that are slick all the way across, most of the sheets resemble T-111.

Durabond and EasySand are the 2 main brands of setting compounds. They come in various set times, the higher the number the longer you have to work with it once it's mixed. Any unused mixed mud must be discarded. Basically it's like regular joint compound except it dries chemically/faster and isn't water soluble. It is harder to sand than regular j/c so it pays to apply it neatly.

 

thank you for clarifying that Mark. I see what you mean, these are all backer boards basically. I thought they were similar to drywall boards, so maybe it's not the best choice then? I mean putting a backer board meant for tiles as balcony wall. I'm going to do some more searching, maybe I don't even have to use any kind of board, maybe I can just put a wire mesh on and apply EasySand directly on it?

 

Occasionally cement board gets finished and painted, usually because of a change in plans but also when the wall has to be more water resistant. I believe it will work for what you want but there might be other choices that require less labor. It all depends on what the customer is willing to accept as the finished product.

In the future it's best to steer customers toward a better product during the bidding stage of the job. They don't always know exactly what they want, just how the finished product should look/preform.

 

All right I will give it a shot, thanks for your help