Drywall Use for "Dry Area" Walls in Bathrooms

[Whitman]

Jerry,

Is greenboard required for dry area walls in bathrooms or, is standard drywall acceptable? By dry area I mean everywhere outside of the tub/shower enclosure. Your help is greatly appreciated.

In case this is a factor, I'm in Florida.

Regards,

Brian Whitman

[Jerry Peck - Codeman]

Brian,

This is from the 2012 Florida Building Code-Residential (the 2012 IRC has the same wording in these sections):
- R702.3.8 Water-resistant gypsum backing board.
- - Gypsum board used as the base or backer for adhesive application of ceramic tile or other required nonabsorbent finish material shall conform to ASTM C 1396, C 1178 or C1278. Use of water-resistant gypsum backing board shall be permitted on ceilings where framing spacing does not exceed 12 inches (305 mm) on center for 1/2-inch-thick (12.7 mm) or 16 inches (406 mm) for 5/8-inch-thick (16 mm) gypsum board. Water-resistant gypsum board shall not be installed over a Class I or II vapor retarder in a shower or tub compartment. Cut or exposed edges, including those at wall intersections, shall be sealed as recommended by the manufacturer.
- - R702.3.8.1 Limitations.
- - - Water resistant gypsum backing board shall not be used where there will be direct exposure to water, or in areas subject to continuous high humidity.

The answer to your question is not as easy as 'yes' or 'no' to "dry areas" - the answer is:
- From R702.3.8: "Gypsum board used as the base or backer for adhesive application of ceramic tile or other required nonabsorbent finish material shall conform to ASTM C 1396, C 1178 or C1278." ... i.e., if ceramic tile is being installed - don't use regular gypsum board; likewise, if the area requires a nonabsorbent finish material (a 'not dry area') - don't use regular gypsum board.

And (or maybe this should be "but"):
- From R702.3.8.1: "Water resistant gypsum backing board shall not be used where there will be direct exposure to water, or in areas subject to continuous high humidity." ... i.e.., don't use moisture resistant gypsum board (MR board/green board) at tub surrounds with a shower or for in showers as the shower sprays the walls and the board behind the surface material (ceramic tile, etc.) can get wet and moisture resistant gypsum board can (will eventually) fail.

You should use cementitious board behind the ceramic tile, etc., for the walls at tubs with showers and in showers. "Durock"TM and "WonderBoard" are two common brands of cementitious board used for this purpose.

The answer is as much where NOT TO USE moisture resistant gypsum board as the answer is where TO USE moisture resistant gypsum board instead of regular gypsum board.

[Whitman]

Thanks Jerry.

My follow up is this. According to The Florida Code, there seem to be exceptions for single family homes for using standard drywall vs. green board outside of the wet area.

Unless I'm mistaken, It looks like drywall may be acceptable outside of the "wet area". Am I misinterpreting this?

Thank you,

Brian Whitman

[Jerry Peck - Codeman]

Brian,

It appears that my first question should have been: What type of bathroom are you asking about? One- and two-family dwelling and townhouse? Apartment and condo?

Makes a difference as to which code go to ... but not really a difference in the use of regular drywall or green board.

The reference you are referring to would be applicable to apartment/condo/hotel/motel buildings - not to single-family homes. Thus the exceptions do not apply to single-family homes ... the exceptions are not needed because there is no requirement for same for single-family homes.
- From the 2010 FBC-Building: (bold and underlining are mine)
- - 1210.2 Walls and partitions.
- - - Walls and partitions within 2 feet (610 mm) of urinals and water closets shall have a smooth, hard, nonabsorbent surface, to a height of 4 feet (1219 mm) above the floor, and except for structural elements, the materials used in such walls shall be of a type that is not adversely affected by moisture.
- - - - Exceptions:
- - - - - 1. Dwelling units and sleeping units.
- - - - - 2. Toilet rooms that are not accessible to the public and which have not more than one water closet.
- - - Accessories such as grab bars, towel bars, paper dispensers and soap dishes, provided on or within walls, shall be installed and sealed to protect structural elements from moisture. For walls and partitions also see Section 2903.

A "dwelling unit" is not the same thing as a "dwelling".
- From the 2010 FBC-Building definitions
- - DWELLING. A building that contains one or two dwelling units used, intended or designed to be used, rented, leased, let or hired out to be occupied for living purposes. (Jerry's note: Think of a "dwelling" as being a one- or two-family home or townhouse.)
- - DWELLING UNIT. A single unit providing complete, independent living facilities for one or more persons, including permanent provisions for living, sleeping, eating, cooking and sanitation. (Jerry's note: Think of a "dwelling unit" as being an apartment or condo.)
- - SLEEPING UNIT. A room or space in which people sleep, which can also include permanent provisions for living, eating, and either sanitation or kitchen facilities but not both. Such rooms and spaces that are also part of a dwelling unit are not sleeping units. (Jerry's note: Think of a "sleeping unit" as being a typical motel or hotel room.)

The FBC-Building requires moisture resistant drywall in areas that the FBC-Residential does not ... then exempts out the same basic area as not being required where not required in the Residential code.
- From the 2010 FBC-Residential:
- - R307.2 Bathtub and shower spaces.
- - - Bathtub and shower floors and walls above bathtubs with installed shower heads and in shower compartments shall be finished with a nonabsorbent surface. Such wall surfaces shall extend to a height of not less than 6 feet (1829 mm) above the floor.

[Whitman]

Thank you Jerry. You've been most helpful.