Drywall FAQ
What is drywall?
Is all drywall made in 4’ x 8’ sheets?
What is greenboard?
What is Durock®?
What is the difference between sheetrock and drywall?
Is drywall fireproof?
Vertical versus horizontal installation – which is preferred?
Parallel versus perpendicular – what’s the difference and why not just hang drywall in the direction that results in less butted seams?
Attachment – Most people know that screws are preferred, but why and why do problems still occur with screws?
What is drywall?
Drywall is a material used to cover wall and ceiling framing. It replaces plaster. It is gypsum, a very common material which is sandwiched between two layers of paper. Drywall is also called sheet rock, wallboard and gypsum board. It is faster to install than plaster and more economical. It is generally not quite as nice and true as plaster, but the economy of the material makes it the top choice in most applications.
Is all drywall made in 4’ x 8’ sheets?
No, it comes in many sizes up to 16 feet long. This reduces the number of joints required to finish the drywall and results in a more attractive finish.
What is greenboard?
Greenboard is a type of drywall made with moisture resistance paper. It is made for use in areas with water present such as bathrooms and laundry rooms. It can be used on the walls and ceilings of those rooms, but not where water is present – for example, on floors and shower or tub walls. In those areas a waterproof wallboard should be used.
What is Durock®?
Durock® is a brand of cement backer board manufactured by the United States Gypsum Company, which is a subsidiary of USG Corporation founded in 1901. Cement backer board is most often used as a subfloor or wall base when installing ceramic, porcelain or stone tiles. Cement backer board is called by a variety of names such as cement board, backer board or tile underlayment. Additionally, some refer to all cement board as durarock, which is a metamorphosed version of Durock®. It is very similar to the way most people refer to all plasterboard as Sheetrock®, which is actually another one of USG’s popular products.
Durock® is composed of an aggregated Portland cement core which is coated with a glass-fiber mesh on one side. The smooth side is used for adhesive applications while the mesh side is used for thinset mortar or mastic application. Durock® can be scored with a utility knife so it breaks easily for do-it-yourselfers who don’t have a saw. When installed, the seams should be scattered. Additionally, the seams must be taped and prefilled with mortar for the best results.
Backer board provides a level and supportive base for glass and ceramic mosaics, tile, stone and brick. Whether using cement board in new construction or remodeling, it may be installed over a wood or steel frame to walls, floors, soffits, partitions, countertops and ceilings. The cement board is fastened with cement screws, self-drilling fasteners or nails.
Durock® cement board comes in two sizes. The 4 inch x 4 inch is 5/16-inch wide and the 3 inch x 5 inch cement board is ½-inch wide. The thinner Durock® offers less support so it may be used for thinner tiles, while the thicker board will be needed for thicker tiles and floors with inadequate support because of the direct pressure applied when people walk on them. The different thicknesses also help maintain even transition areas on the floor.
One of the most common areas to use Durock® is in the bathroom because it is mold and moisture resistant. Cement board is necessary where water may run on the floor, but it is mandatory for tiled showers or tiled areas above a bathtub. Durock® may also be used in pool areas or saunas. It also has applications in the areas around fireplaces and wood burning stoves. The product is noncombustible and it will not swell, soften, decay, delaminate or disintegrate according to the manufacturer.
What is the difference between sheetrock and drywall?
There really isn’t any difference. Sheet rock, wallboard, gypsum board, gib, gyproc, and drywall are all generally the same material used for the same purpose.
Is drywall fireproof?
Drywall is not fireproof but it is fire resistant. There are three levels of fire resistance. The first is standard drywall which has the lowest fire time rating. Type X drywall which is normally thicker than regular drywall and with additives can have a 90 minute fire rating. And there is also a Type C drywall composition that can have a fire rating of up to 2 hours.
Vertical versus horizontal installation – which is preferred?
In residential construction where the walls are 9-ft high or less attaching the drywall horizontally can reduce the lineal footage of seams by as much as 25% over vertical attachment. On higher walls like in a stairwell or on the end wall in a cathedral room, horizontal is still the way to go. Transitions areas such as the floor joist beams or top plates of walls where studs continue on to the rafters can be spanned so that seams are located off these areas. Horizontal attachment also increases shear strength of the structure and seams are usually at a more convenient height for finishing.
Parallel versus perpendicular – what’s the difference and why not just hang drywall in the direction that results in less butted seams?
The accuracy of on center spacing of the framing is very important if attaching drywall parallel in joists on ceiling. Cutting the beveled edge off so the seam lands on a joist is really not an option as far as the finisher is concerned. Drywall is approximately 3 times stronger in the long direction. Accordingly, drywall hung perpendicular to the framing is stronger than drywall hung parallel, so it is less likely to sag. If attached, perpendicular lengths can be cut so that the butt seams fall where desired. Yes we are always trying to avoid butted seams, but an occasional butt seam is better than a ridged seams running the length of the ceiling or sagged drywall between joists. Perpendicular gives the structure greater strength. Drywall floats over slightly uneven joists, making them less conspicuous.
Attachment – Most people know that screws are preferred, but why and why do problems still occur with screws?
Screws are faster to install than nails, they do less damage to the drywall panel when set, and they hold the drywall tighter against the framing. If a screw is set too deep it has torn the face paper and is weaker. If the framing the drywall is being attached to is bowed in the screw may not be able to pull the panel tight so if the walls moves or is hit the screw will pop loose. If there was poor heat or humidity when the drywall work was being done and then the heat is turned on and the humidity lowered then lumber shrinks more than the drywall and screws pop loose. Screws only need to penetrate the framing 5/8 of an inch, longer screws are more likely to pop if lumber shrinks. Drywall is affected by settling and structural movement which can cause screws to show.
Citation: http://thatdrywallguy.com/ferguson_drywall_innovations_inc_005.htm