# smooth hard non-absorbent surface requirement on walls around urinals & water closets



## Jonathan (Jan 22, 2013)

I know this topic has been gone over before, but it's still not clear whether or not some kind of epoxy or enamel coating over gyp bd. would comply with the intent.

My take is no way, not ever! because even if the coating could be considered hard it could still be cut or gouged or otherwise compromised causing the drywall behind it to absorb moisture.

Anyone care to comment?

Would 7/8" exterior cement plaster over paper backed metal lath with a smooth finish and epoxy or enamel coating work?


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## steveray (Jan 23, 2013)

Whatever the AHJ will accept...is acceptable....cement plaster should work.....


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## ICE (Jan 23, 2013)

Jonathan said:
			
		

> Would 7/8" exterior cement plaster over paper backed metal lath with a smooth finish and epoxy or enamel coating work?


The coating would stand up to abuse on plaster better than it would on drywall.  I have seen it done with split face CMU.  It was applied thick enough to smooth out the irregularities on the concrete surface.


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## rktect 1 (Jan 23, 2013)

Oh God.  I think your responses to this will vary greatly.  I wont accept it.


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## fatboy (Jan 23, 2013)

No way on drywall.......

"Would 7/8" exterior cement plaster over paper backed metal lath with a smooth finish and epoxy or enamel coating work?"

I would accept that.


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## Jonathan (Jan 23, 2013)

7/8" exterior cement plaster with coating (epoxy or enamel) or paint over gyp bd.?



			
				rktect 1 said:
			
		

> oh god.  I think your responses to this will vary greatly.  I wont accept it.


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## Yikes (Jan 23, 2013)

Jonathan said:
			
		

> My take is no way, not ever! because even if the coating could be considered hard it could still be cut or gouged or otherwise compromised causing the drywall behind it to absorb moisture.


I submit that tile, FRP, or other such materials are also subject to cutting and gouging... it's just a matter of degree of force, and the code does not describe any durabilty requirements.  the only requirements are smooth, hard and nonabsorbent.


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## rktect 1 (Jan 23, 2013)

And if I can push a thumb tack through it, it just is not a hard surface.


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## Jonathan (Jan 24, 2013)

Want to try something a little unconventional.

Q: What is the correct thickness of stucco?

A: Stucco thickness depends on the backup system and on whether or not lath is present. In ASTM C 926, the Standard Specification for Application of Portland Cement-Based Plaster, thicknesses are provided for scratch, brown, and finish coats.

Over frame construction, lath must be used. Over solid substrates—which include concrete masonry, cast-in-place concrete, and precast concrete—lath is sometimes used. When lath is present, three-coat plaster is recommended. Note that frame construction—metal or wood studs—may or may not have sheathing present, but that plaster thickness is independent of sheathing. With lath, total plaster thickness is 7/8 in.

Three-coat work can also be specified for solid plaster bases without metal lath. The correct thickness is then 5/8 in.

Two-coat applications are only for use over solid plaster bases without metal lath. For unit masonry, that thickness is ½ in. For cast-in-place or precast concrete, the thickness for two-coat work is 3/8 in. These are direct-applied systems, meaning that there is no metal lath involved.

It is important to note that the committee in charge of ASTM C 926, the reference document for this application, has decided to keep the term “nominal thickness” in the title of the table for two- and three-coat work. This term takes into account that walls are built to certain tolerances and may not be exactly plumb or plane. The reference to a nominal thickness allows for small variations from an exact dimension. The intent of the specified thickness is to provide a reasonable system that, over many years, has proven itself to be weather resistant and durable. Local building officials should be consulted for further information about variations from the specified thickness.

See ASTM International - Standards Worldwide for information about ordering a copy of ASTM C 926, which contains the recommendations for both vertical and horizontal plaster thickness over metal plaster bases and solid plaster bases.

I would like to use 1/2" hardibacker board and the three-coat work noted above without metal lath adding 5/8" to the 1/2" hardibacker board. with a smooth finish coat.

Any reason why this wouldn't work?


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## globe trekker (Jan 25, 2013)

> Any reason why this wouldn't work?


Suggest you contact the AHJ for their interpretation before you proceed!   They may want

something totally different.

Also, welcome to the Building Code Forum!  

.


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## fatboy (Jan 25, 2013)

I agree, check with the AHJ. Again, I would accept what you are describing.


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## David Henderson (Jan 25, 2013)

Jonathan without the lath how do keep the plaster on the wall whick is the purpose of the lath.


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## Jonathan (Jan 25, 2013)

Thank you globe trekker!! This is my kind of place

I went ahead and did it. Tried to upload a jpg, but not sure if it worked.


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## Jonathan (Jan 25, 2013)

David,

It should bond to the 1/2" thk. cement board, Durock or Hardibacker board.


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## Jonathan (Jan 25, 2013)

Can't figure out how to upload a jpg. file.

I can get it into the dialog box from my computer but after that the only option is to close the dialog box.


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## Jonathan (Jan 25, 2013)

Okay, think this jpg image of my details will tell the story

View attachment 662


View attachment 662


/monthly_2013_01/572953c6a3cef_SignatureFlightSupportplasterwainscot.jpg.74fb2caf87f47febac049422b69fddea.jpg


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## Jonathan (Jan 25, 2013)

Awful image quality, but the first detail shows the tile floor & tile wall base up to 6" and then the plaster over cement board up to 48" with gyp bd. over that to ceiling height.

I like this option better than the Fiberglass reinforced panels. Tile wainscot doesn't fit the budget. It's a sad state of affairs...


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## Architect1281 (Jan 25, 2013)

Smooth hard? Soft Porous? are we talking about the wall or the weapon . So when you have a single fixture WC mens room would you want to be the cleaning crew?


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## Jonathan (Jan 26, 2013)

1281,

Your point is?

A

smooth plaster finish coat very hard surface by nature with a high quality epoxy or enamel coating sealer provides the required smooth hard non-pourous surface

easy to clean too


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## Jonathan (Jan 26, 2013)

AHJ=agency holding jurisdiction?


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## fatboy (Jan 26, 2013)

Close...........Authority Having Jurisdiction


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## mark handler (Jan 26, 2013)

Jonathan

Many building departments will allow enamel paint... most health departments will allow certain "types" of epoxy paints.

Make sure whatever you use, it is urine resistant. There are enamel paints and epoxy paints/coatings that are not urine resistant.


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## Jonathan (Jan 26, 2013)

Thank you!!


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## Jonathan (Jan 26, 2013)

mark handler said:
			
		

> JonathanMany building departments will allow enamel paint... most health departments will allow certain "types" of epoxy paints.
> 
> Make sure whatever you use, it is urine resistant. There are enamel paints and epoxy paints/coatings that are not urine resistant.


Good info. Thank you!!


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## Jonathan (Jan 26, 2013)

fatboy said:
			
		

> Close...........Authority Having Jurisdiction


Got it, Thank you!!


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## Jonathan (Jan 26, 2013)

David,

It will bond to the 1/2" thk. cement board, Durock or Hardibacker board. The cement board does the job of the metal lath in this case.



			
				David Henderson said:
			
		

> Jonathan without the lath how do keep the plaster on the wall whick is the purpose of the lath.


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## Jonathan (Jan 27, 2013)

ICE said:
			
		

> The coating would stand up to abuse on plaster better than it would on drywall.  I have seen it done with split face CMU.  It was applied thick enough to smooth out the irregularities on the concrete surface.


I have seen this too, rest stop on freeways & public park bathrooms come to mind.

I like the idea of being able to use cement board over a moisture barrior w/ a 5/8" stucco application over with a smooth finish coat and coating as you discribe above.

Something that is cleanable and able to hold up to exposure to urine.

Thank you for your input!!

The budget is so tight the contractor can't make it work with ceramic tile, and I prefer this system over FRP


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