Since the 1950s or 1960s, most homes built have the interior walls finished with drywall, more correctly known as gypsum board. “Sheetrock,” the common name for gypsum board, is actually a proprietary name for gypsum board manufactured by USG (United States Gypsum Corp.). This relatively inexpensive engineered material was developed as a replacement to plaster and lath walls. It provides a smooth, paintable wall for a fraction of the effort of plaster and lath and once properly finished, textured and painted it really can’t be distinguished from plaster.
Drywall sheets come in the same size as plywood (4’x 8’) and are usually 1/2 inch thick, although 1/8”, 1/4”, 3/8” and 5/8” thicknesses are also available. The long edges of the sheets are indented, forming a channel for taping the joint. This way, the tape and drywall mud won’t produce an obvious protrusion. However, some slight protrusion is necessary when taping the short ends or cut pieces, because they don’t have this indentation.
It is customary to install drywall horizontally for walls, allowing the “hidden” joint to run horizontally along the wall. The ends of the sheets are staggered when installed, usually giving them a four foot offset. This is important, as a short vertical protrusion is less visible than a longer one and a horizontal protrusion running all around the room, halfway up the wall, would be much more obvious than the shorter vertical ones
Benefits of Drywall
The major impetus for developing drywall was the cost savings that was generated by reducing the skilled labor needed to finish walls. While taping and finishing drywall still requires a fair degree of skill, it is a lower level of skill and requires much less time than nailing up lath strips, applying the cement inter-coating and then floating the plaster on top of that.
In the beginning, drywall was slow to gain popularity, being seen by many as a cheapening of the workmanship that was going into the home; but it eventually took hold. Today, it is the standard means of covering interior walls, although it is not the only way that interior walls of homes and offices can be covered.
Benefits of Plywood
Plywood offers some distinct advantages over drywall and is a good alternative to be considered, especially if one is looking for a warm, natural look. The sterility of drywall doesn’t provide much warmth, whereas wood grain naturally does. So, what are these benefits?
When we talk about plywood walls, we often use the term “paneled walls.” This refers to thin, inexpensive wood paneling, which is often printed to look like wood grain. However, we can also use finer grade plywood, such as ½” or ¾” cabinet grade plywood as wall covering as well. Many upscale homes and corporate boardrooms have walls covered in this manner. The look is considerably different than the low cost wood paneling, providing a “richness” that drywall can’t match.
- Lower weight – Plywood is actually lower weight than a comparable sheet of drywall. A 5/8″ sheet of drywall weighs 2.75 pounds per square feet, while a 5/8″ sheet of plywood weighs from 1.8 to 2.1 pounds, depending on the type of plywood.
- Easier installation – Plywood can be used naturally, without the need for taping and finishing. The only finish most people apply is a couple of coats of varnish. If hardwood plywood is used, the grain patterns provide a distinctive and attractive finish, without any fancy painting techniques. Plywood can be attached to the wall with a number of different fasteners, depending on the “look” one is trying to create.
- Resisting damage – Plywood is considerably stronger than drywall. You can easily break a drywall wall, either from simple horseplay or from hitting it with a piece of furniture while moving in. Granted, damage to drywall is easier to repair than damage to plywood, but it’s better to not have the damage to worry about. This is especially good for laundry rooms, garages and other “utilitarian” spaces within the home.
- Structural strength – If you’ve ever tried hanging a heavy picture or mirror on the wall, you understand how structurally weak drywall is. You really can’t count on the drywall to carry the weight, but must instead find a stud to nail the hanger into. With plywood, you can attach pictures, mirrors or even shelves anywhere, without a risk of the wall breaking or the attachment falling off.
Installing Plywood Interior Walls
Real plywood walls are installed over drywall, in cases where fire code requires a “one hour burn through wall,” such as in adjoining residences. However, if this is not a requirement, it can be attached directly to the building’s structural studs. The plywood is applied with a combination of adhesive and nails. The adhesive is the main fastener, with the nails being used mostly to hold the plywood panels in place, while the adhesive sets.
To install plywood onto existing walls, first check that they are plane and smooth. You may need to sand the joints in the existing plywood or add drywall mud to raise low spots, in order to have a plane and smooth wall to attach your plywood to. Remove any trim or electrical cover plates.
Cabinet grade plywood, used to cover walls, should be installed with the panels mounted vertically. Before cutting and installing any panels, measure and lay out the wall carefully. You may find that the dimensions of your room require a thin strip at one end of the wall. Instead of that, you may choose to cut two panels, making each slightly wider than a half panel, so as to avoid having that narrow strip. You’ll also want to cut out for windows, doors, light switches and wall outlets, before installing.
Always acclimate your plywood to the room, before mounting it. Having the panels in the room for 24 hours to adjust to the temperature and humidity is sufficient.
To install the plywood, first use a caulking gun to apply adhesive to the walls. You’ll want to apply about a one inch circle of adhesive, every ten inches. It is not necessary to use large amounts of adhesive, making lines on the wall. Only apply enough adhesive for one panel at a time, so that it doesn’t dry before you can get to it.
Align the plywood sheet to that section of the wall and press it up against the wall, crushing the glue between the plywood and the existing wall and leaving a 1/16 inch gap between panels. Then nail the panels to the wall, top and bottom, with finish nails. Nails should be used every 12” and in all corners. It is not necessary to nail along the long edges of the sheet, as long as you have pressed it to the wall and have nails in the ends.
Finish the plywood by staining and/or varnishing it. Plywood can also be painted with a latex paint; but why would you want to?
Another finish option for plywood walls, which works very well for plywood ceilings as well, is to cut battens and install them over the plywood, making two foot squares. You’d want to cover your seams with this, of course, but by doing the two foot grid, you make it look decorative, not just like you’re trying to cover up anything. Staining them in a contrasting color to the plywood adds to the aesthetic appeal of this style ceiling.
Wood plank, another alternative
Another option is to use wood planking as a wall covering, rather than plywood sheets. You can either buy wood flooring planks or imitation wood flooring planks, use dimensional lumber such as 1”x 4”s or 1” x 6”s or if you have a band saw available to you, you could resaw 2”x 4”s to make your own 1/4” thick planks.
The most expensive version of this style wall is to use the wood planking or imitation wood planking designed for use as flooring. This higher overall cost is offset somewhat by convenience, as those boards will be tongue-in-groove, helping guarantee a good fit and finish and will probably be adhesive backed, making it possible to install them by nothing more than pressing them up against your existing wall. Just make sure you have a smooth, clean, non-textured wall for the planking to adhere to.
One of the nice things about doing this sort of wall treatment is that when you are staining the wood planks, you can use a variety of different stains, giving a lot of visual variety to the planks and making for a very attractive wall. Staining should be done before any of the planks are installed on the wall.
Regardless of what sort of planks you choose to use, you’ll want to stagger the ends while installing, just as you would for a hardwood floor. This will require you making some random cuts in boards, so that you get the feeling of using random stock. Avoid following a pattern in your cuts. Also, be sure to cut the factory end of the board, before installing it or measuring, as these are not always square to the long edges.
The boards can be nailed to the existing wall, using a pneumatic brad or finish nailer. It is not necessary to use a lot of nails, as there is not going to be any stress on the wood planking itself. Anything attached to the wall should go through the planking, into the studs behind it.
One advantage of using wood planks over plywood is that if you’re a bit creative, you can create an attractive wood wall much less expensively. Using pallet wood or construction grade 2”x 4” boards, that you resaw yourself on a band saw, allows you to get the necessary materials for very low cost. You may have to cut out some unusable sections of the boards, but it’s worth it, in order to save that much money. Besides, that will help you to have random lengths of boards.
Advantages of Drywall Over Plywood
There are several advantages to installing drywall, rather than plywood. The first is cost. Plywood is considerably more expensive than drywall, especially if you are using cabinet grade hardwood plywood. This is a large part of what has kept plywood from being used more consistently as an interior wall treatment.
The second advantage is that drywall is considerably easier to cut and install than plywood. Plywood must be cut with a saw; for construction, this usually means a handheld circular saw. It requires some degree of skill to make those cuts evenly. On the other hand, drywall is cut by scoring the desired “cut line” with a utility knife, cutting through the paper covering. The sheet is then bent, breaking the sheet to the desired length. Irregularities can easily be corrected with a surform hand plane.
Thirdly, drywall is much easier to finish smoothly, than plywood is. While cabinet grade plywood is usually sanded smooth, the dry plywood is highly absorbent. The first coat of paint or varnish applied soaks into the wood, merely sealing it. Drywall’s paper coating is somewhat moisture resistant, allowing that first, sealing coat, to also be part of the final finish.
If plywood is to be finished like drywall, it is difficult (but possible) to get as smooth a finish, as the drywall mud causes the grain to rise. If it is stained and varnished, the first coating of varnish does the same, creating a need to lightly sand the entire surface of the wall, before applying an additional coat. The only sanding required for drywall is sanding the drywall mud smooth, blending it into the surface of the drywall.
Finally the last advantage drywall has is that plywood may not meet the fire-resistance requirements of local building codes. If the building code requires that an interior wall have a one hour fire resistance, as is common between garages and living areas or between adjacent living areas, plywood is not able to provide that. However, a wall built with 5/8″ drywall on both sides does meet that building code requirement. So, if you wanted to use plywood for aesthetic reasons, you would need to mount the plywood over a layer of drywall.
Disadvantages of Drywall
The main disadvantage of drywall is that it can be easily damaged by water. While pretty much any wall will be damaged by flooding, drywall will all but disintegrate, requiring messy removal and total replacement. Water wicks up the drywall, causing damage well above the high water line. Once the paper covering is weakened by the water, the weight of the gypsum inside is enough to cause the drywall to start breaking and falling off the wall. On the other hand, plywood walls will survive flooding, although there is a good chance that they will suffer damage.
Drywall also has a fairly low resistance to impact. You are much more likely to put a hole in drywall when moving a piece of furniture or hitting it with your hand, than you are to put a hole in drywall. This is an important consideration, when selecting a wall treatment for use in industrial areas or heavy traffic areas in your home, where such impact is likely.
Drywall can be installed over wood or metal studs. In the case of metal studs, screws must be used. When installing over wood studs, either screws or nails may be used, depending on the installer’s preference. However, screws should be used whenever installing drywall on ceilings, so that the weight of the drywall doesn’t pull the nails loose. Screws or nails should be installed eight to 12 inches apart on all studs. Both nails and screws should be driven slightly below flush.
Using screws on drywall can be slightly tricky, if you are using a drill/driver or impact driver. You’re better off using a screw gun, which is designed specifically for this purpose. The nose on the screw gun ensures that the bit disengages from the screw at just the right depth, below flush, but not breaking through the paper.
When both walls and ceiling are to be covered with drywall, the drywall is installed on the ceiling first, allowing the sheets to run the long way for the room. Drywall sheets installed on the walls should be installed horizontally, starting with the top sheet, which must but up against the drywall on the ceiling. It is best to stagger the joints on the walls, from the joints on the ceiling, so as to hide them better. The lower course of drywall is then installed on the walls, staggering the joints from the upper course. This should leave a slight gap (about ½ inch) between the bottom of the drywall and the floor.
The joints between individual sheets should be as close as possible, but drywall is much more forgiving in this regard than plywood is. Gaps of up to ¼ inch can easily be covered in the taping and finishing process. Always ensure that the ends of sheets land on a stud, with adjacent sheets each taking half the width of that stud, so that both can be attached to it.
With the drywall installed, the joints are taped, using drywall mud and finishing tape. There are two types of finishing tape available:
- Paper tape – which requires drywall mud below it to act as an adhesive and above it to provide a smooth finish
- Fiberglass tape – which is self-adhering and only requires drywall mud over it to provide a smooth finish
Typically, three layers of drywall mud are applied over all taped joints and to cover the fasteners, with the top layer being a finer “finishing compound.” These layers are applied with successively larger drywall knives (essentially a wide putty knife), so as to create a wider and wider joint. The layers are allowed to dry and are sanded between applications. The idea is to create a joint which rises so gradually and so smoothly, that it is not visible.
With the final layer of drywall mud applied, dried and sanded, the walls and ceiling are ready for texturing. While there are several ways of doing this, the most common is to use a texture gun to apply “orange” peel or “knockdown” texture to the walls and “popcorn” texture to the ceiling. Both wall texture and ceiling texture are readily available wherever sheetrock is sold.
Installing drywall over plywood
Drywall can be installed over ½ inch plywood. This is done so that the plywood can act as a noise barrier, absorbing sound. Plywood is better for this than drywall, because it is not as dense.
When doing this, CDX grade plywood or OSB is normally used, as there is no advantage of using more expensive grades of plywood. Install the plywood sheets to the wall or ceiling, just as you would do if all you were installing were the plywood. Then, install the drywall over the plywood, as if you were installing it over studs, without the plywood there. Finish the drywall normally.
Installing drywall on curved walls
Drywall comes in thin sheets, specifically created to allow the drywall to be used on curved surfaces. If you want to install a curved archway, make a curved wall in a room or put an arched ceiling in a hallway, you can do it with 1/8 inch thick drywall. However, you cannot do compound curves with it, as it can only curve in one direction at a time.
If you’ve ever carried drywall or installed it, you’ve probably noticed that just like plywood, the sheets will flop around, curving. This is even more pronounced with 1/8 inch thick drywall, which is designed specifically for making those curved walls, archways and ceilings.
The hard part in making these curves is creating the structure to support them. You don’t have to have a full curve underneath the drywall, but you do have to have enough attachment points to support the drywall as it makes the curve. Those attachment points are normally 2”x 4” studs, although you may find that you need to cut some out of double layers of ¾ inch plywood.
The 1/8 inch drywall is attached to the 2”x 4” framework, just as normal walls and ceilings are, curving it to fit. Make sure that the edges are firmly attached, as that’s where the greatest stress will be. Apply additional layers of 1/8 inch drywall, over the original one, adding strength. Stagger the seams, to help make smooth transitions where the end of one sheet and the beginning of the next aren’t obvious. Finish just as if it were a flat wall or ceiling.