Fastening Techniques
For nails, drive the nail straight and set the
head below the surface by making a dimple in the surface with the hammer.
It doesn't take much of a set to allow the head to be covered with compound. To
tell if the nails are set properly, run a putty knife over the surface and
listen for ticks, indicating a protruding nail. The nail should be no
closer to the edge of the sheet than 3/8" to keep
from splitting the edge. Fastening with screws is done roughly the same way. To
keep from bowing the sheet, tack it in place and then fasten from the center
out. Press the sheet against the framing as you drive the fastener.
If you drive a nail or screw and it does not hit wood, you can remove it
and try again. But with a nail, it is easier to set another nail next to
it to hit wood and overlap the bad nail to keep it from popping out later.
Never leave a loose nail or screw in the drywall!
If you find that the studs do not line up
well (some are bowed), the usual correction is to use drywall shims. These are
cardboard strips 1-1/2" wide that you can buy in a bundle. Use a straightedge
over the studs to find the low spots, and tack or staple a shim to correct it.
Not uncommon to have to cut the shims to a suitable length and even stack them.
Then as you fasten the drywall to the studs, the shims will be held in place.
Driving screws in steel studs is more difficult since
the stud tends to deflect. For joining two sheets over a steel stud, you
must first set the screws in the open edge of the stud to pull the stud
against the drywall.
Compound
I use mostly the multipurpose compound that comes
in 1 gallon and 5 gallon plastic pails. You can use it as-is for the initial
taping, unless it is just too stiff to be workable. For the second coat, it
is best to thin it slightly with water. For
a small job, you can do this mixing in a drywall pan; for a large job, you
will want to mix in the pail using a large "potato masher" tool or a power driven
mixing paddle. It takes a very powerful drill-driver to power the mixing paddle;
a corded 1/2" driver will usually do it. Make sure you do not run the mixing
paddle too fast or it will make small bubbles in the compound, and these will
mess up the finish. You can get inexpensive plastic pans
with metal edges for scraping the knife clean, but I don't recommend these.
A stainless steel pan costs just a little more and is much easier to use and to clean.
Some pros believe almost fanatically in buying
premixed compound in a cardboard box (with a plastic liner); I believe
these contain 3-1/2 gallons. You save maybe a dollar or so per unit, but you
end up leaving some in the bottom that you cannot get out, and it is more
difficult to get it out. I see some dump the material out of a box when they
first open it into an empty plastic pail. IMHO it just isn't worth the
hassle and the wasted time. Besides, the 5 gallon pails are easy to handle
and easy to wash out when empty; they are very useful around the house.
For the final layer of compound, you may wish to
use topping compound; this uses a finer material and it feathers out nicer
as a result. Unfortunately it is sold mostly in the cardboard boxes here. When
I get some, I dump it into a 5 gallon pail right away, and label it. But I usually
just thin the multi-purpose compound.
There are fast drying compounds that are claimed
to dry hard in 20, 40, or 60 minutes, without shrinking; they come in powder form and
must be mixed with water. These are setting compounds rather than the typical drying
compounds. That is, they set up like plaster. I don't think they work any better than
normal compound for taping. They may set up so that they can be sanded in the claimed
time but they usually mess up the sandpaper and they take a day to dry enough to
paint. The value of these is to a plumber, for
example, who wants to patch a hole he made in a wall so he can leave it smooth.
But the patch will have to cure or dry thoroughly before it can be painted. The
plumber usually does not do the painting, so he is home free in short order.
The one
place where the fast dry compounds are very useful is in patching plaster, since
they seem to be more compatible with plaster than regular drywall compound. I
let the patch dry overnight before sanding so it doesn't foul the sandpaper. Since
this type compound does not shrink, it works well for plaster patching, and tape is
not required for the joint. If the plaster is old and dry, coat the edge of it
with white glue or latex additive before patching to assure better adhesion.
For deep areas, compound takes long to dry and
will shrink or crack; that would require that you add more compound to that point the next day.
There are a couple ways to speed up the job. One is to use the fast dry compounds.
Another is to use a fast dry patching compound like FixAll or Quik-Fix. I believe
FixAll is now called Fit-It-All. This adheres well and dries fast, but it doesn't
sand smooth, so leave a little recess over it to finish off with compound. Fix-It-All
will set up enough to work over in 15 to 30 minutes; then apply the compound.
The compound will probably discolor tan over the Fix-It-All but this will
be covered by the primer. What I do is go around the job and fill the deep
patches needed with Fix-It-All first and then do the overall tape and fill with compound;
by the time I come back around with the compound, the Fix-It-All is dry enough to
go over.
Taping
The whole purpose of the tape is to assure
that the compound fill over a joint does not crack or split. Paper tape
is the old standby, but it can ruin an otherwise good job if it does not
adhere to the drywall. This happens a lot, and it may not show up for
some time. Some old timers doing patch work will dip the paper tape in
a bucket of water to wet it before applying it, and this does work. However,
it is better and faster to use the mesh tape instead. The mesh tape self-adheres
to the drywall, so you can tape the whole job before you even get out
the compound. Then spread compound over it. This is very reliable; the
only difficulty you may experience is that the tape may bunch up and wrinkle
if you press too hard while filling. This is easy to correct by just pushing
in the opposite direction with the knife. Using the mesh tape on the factory
recessed edge, you should be able to get the joint absolutely flat.
Some argue that the mesh tape is not as strong as
paper tape. My experience is that the joints can be nailed or screwed
adequately to assure that the drywall will not shift. Then the strength
of the tape does not matter. Conversely, if the drywall is not fastened
well, or if the structure is not properly fastened together, either type
of tape will split or lift off. I have modified walls that were taped with mesh tape
and found the joint very strong; the tape was hard to get off.
Be careful using the mesh tape on inside corners.
You must press the tape completely into the corner so the corner will be square
and the tape will be covered with compound. You can do this with a putty knife if you
are careful not to cut or weaken the tape, but I find it better to use a corner tool
(see below).
For taping, you will probably want a 4" putty
knife and a 10" or 12" drywall knife. You can use the wide knife as
a hock to hold compound and apply it with the putty knife. Then smooth
it with the wide knife. Keep the edge of these tools clean of drying compound
or it will mark the work. There is a technique of using the wide knife
that you need to learn. When you smooth the outside edge of the compound,
twist the knife so it bears hard on the drywall and only lightly on the
compound. This will feather the edge nicely, without leaving a mark.
Realize that it usually takes three coats of compound to do the taping;
it is near impossible to do it with one coat, and consider
yourself fortunate if you can get by with only two coats.
Butt joints are tough to do well and that
is why you want to reduce the number of them. A pro
would go over the tape with an ever increasing width of compound so that the hump
is hard to see. For you, if you are not trying to meet a production quota, the better
idea would be to cut away the face of the drywall paper back about an inch or more
on each side of the joint
so you can create a recess in the face for the tape. You may still have to build up
a wide hump of compound, but it would be greatly reduced.
There is a special drywall corner knife that is
very handy for inside corners. Even if you have only one inside corner to do,
I recommend you get one of these; they are not expensive and they will save you
from some exasperation. Use it first to smooth the tape in the corner. Then apply
the compound on both sides of the corner with a putty knife or small drywall knife,
over the tape, and then do the smoothing with the corner tool. If the outside edge
of the compound is not smooth, use a wide putty knife or drywall knife to feather it.
This method is fast and makes a neat joint.
Outside Corners
Standard covering for corners is metal corner
bead. You nail it to both surfaces; there are nail holes in the flanges, but most
pros nail through the metal. While it seems simple enough, it takes
some care to get it right. Start in the middle of the wall vertically and use a
straightedge of some kind, even a drywall knife, to assure that the corner sticks
out slightly farther than the flanges. Then work up and down from the center. When
through, check with the drywall knife to be sure the flanges do not protrude. When
you fill over this, the knife will ride on the corner and back a few inches on
the wall. You can use screws on the corner bead, but it is much harder to do. Use this
same technique around windows and other openings.
Bull nose corners are done much the same way;
just use the correct corner bead. You have to use some care to miter cut intersecting
corners. I hear that the plastic bull nose corner bead works better in that if it
is later banged, the dent will pop back out, where the metal bull nose will not.
There are self-adhesive paper backed corner beads but I used them once, and that
was enough! The paper gets in the way and gets sanded too easily, and that makes
a fuzzy mess. Same for paper-backed corner bead that is held on with compound.
Wall Ends & Arches
On wall ends you will have corner bead on both
edges. When you fill that, the knife will ride on the two corner beads like rails
so you need to be sure the two corner beads provide a square guide.
Arches are similar in that you will want two
corner beads for guide rails. There are several ways to make an arch, and you
may even be able to buy an arch form that will fit. Here is one simple way to make an
arch: Cut the two sides out of 1/2" plywood with a jig saw and block them to the thickness of
the framing. For example, if this is a 2x4 stud wall, the outside thickness of
the blocked curve forms would be 3-1/2"; you can use 2x3 stud material for the spacers.
Cut the arch sides and the blocks for the
sides and top. Fasten these blocks and one plywood side in place with deck screws.
Then fasten the other side to the blocks. Cut several blocks for the bottom curve
with the grain running crosswise. You can virtually fill the curve with these blocks,
if you wish, or you can space them. This will give you a solid frame for the drywall.
Hang the drywall on the wall surfaces and over
the curved arch faces; make this a continuous piece of drywall so there are no joints
that might crack. You can hang the drywall and cut the curve after it is in place.
Now fill the bottom with a strip of drywall; wet it on the outside of the curve so it
will bend to fit the curve, and tack it in place. It will not need to be perfectly
curved because the drywall fill will be gauged by the corner bead. You will need
bendable corner bead for the two curved corners, and it would be best to run it down the
wall a few inches before connecting to the vertical straight corner bead pieces. If you
are using standard metal corner bead, you may be able to splice the corner bead pieces
with the shank of a 4p nail in the corner.
Sanding
I don't know of a simple and cheap way to
power sand drywall. The trick is to do a careful job of filling so
minimal sanding is required. Use a drywall sander; this is an inexpensive
pad roughly 4x10" with a foam rubber face and a handle. The sandpaper is a
special black silicon carbide that is die cut to fit the sander; after you
fasten the sheet to the sander, lightly fold the edges of the paper over the
long edges of the sander to get into corners. I use 80 grit for most work.
Some people prefer sanding screens rather than sandpaper. These are a mesh like
screenwire, coated with the silicon carbide grit; they claim it does not load
up as rapidly as the paper. You can get
similar sanders on a pole for ceilings, but they are hard to control because
you aren't close enough to see what you are doing. Keep the sanding to a
minimum so you don't fuzz up the drywall face. If I am working on a wall where
there is some question, I will hold a flashlight near the surface so I can
see any imperfections; the glancing light will make them stand out.
Some people talk of sanding with a wet sponge.
My experience is that it doesn't give a surface flat enough to suit me and I
don't recommend it. It will give a smooth surface, but not flat.
After the final sanding, you need to wipe the
dust off the surface. You can do this with a rag, even a slightly
damp rag. A neat idea I read about is to use a dry Swiffer floor dusting
tool; they cost less than $15 and have a long enough handle to reach
ceilings. If the dry pads load up too readily, wrap a rag around the tool.
Skim Coating
This is laying a thin coat of compound over all
or most of the surface, and is usually done to cover a damaged surface or unwanted
texture. This would be the method to patch a wall that was damaged by removing
wallpaper or paneling. It is not a technique that comes naturally to most people;
it will take some practice. The surface has to be sound and joints must be taped.
Doing this over a small area is not difficult, but over a whole wall, it is a
real challenge to get the surface flat. Unfortunately you may not be aware the surface
is not flat until you paint it. One way of assuring that it is flat is to use a straight
edge as a screed. Run it from different directions until you are satisfied.
If some of the surface was painted with an enamel (latex or oil) it will have to be
roughed up some with coarse sandpaper so the compound will adhere properly. Mix the
compound so it is just a bit thinner than it comes out of the bucket, so it spreads
easily. Then apply with either a drywall knife or trowel; a trowel is best. A drywall
trowel has rounded corners so it will not gouge or leave marks. If you cannot find
a drywall trowel, you can take a rectangular trowel and round the corners with a file
or grinder
Texturing
This is messy work; cover things with sheet
plastic to protect them. For a large area, a hopper gun with compressor is
the best tool; you can rent or buy one. Mix compound real soupy and select the
proper nozzle. In general, the large nozzle opening gives a coarse spray and the
small nozzle gives a fine spray. You will also have to adjust the pull of the trigger
some to optimize the spray. These give an orange peel spray most easily. You lay on
the spray to pretty well cover the surface.
By adjusting the pull and using the larger nozzle, you can get a
knockdown texture. For this you throw gobs of material on the wall
randomly, let it set up some, and level it (knock it down) with a trowel
or drywall knife.
Here is how to mix the compound
for a hopper gun. It takes roughly 20% water mixed in the compound. Mix it
thoroughly with a big "potato masher" mixer that you can get at a home center.
When you pull it out of the compound, the compound should mostly fall off of it.
Now strain it with a large kitchen strainer as you pour it into the hopper.
It will not easily go through the strainer, but can be coaxed with a couple fingers.
Be aware that this is hard on the strainer and may rust it.
I bought a hopper gun at Home Depot years
ago (about $65) and it was difficult to use and very unreliable.
I ended up breaking the trigger handle. Got another one with about the
same result and took it back. Then I went to a drywall supply house and
got a pro model that worked just great, for about $75, and I still use it.
I ended up putting a shutoff valve for the air supply on the hopper but
otherwise use it as it came out of the box.
For a small job you can use the aerosol spray
can texture; there are several types, even one for patching popcorn
ceilings. The nozzles on the water based Homax brand work best for me, but
read the label carefully since they offer several products with different coverages.
The prices for the spray texture have gone up so you would not want to do a large
area this way. They also market a fast dry (oil based) texture that is terribly messy;
requires solvent for cleanup. Avoid it.
Homax offers a simple power texture gun
that uses a separate compressor. I have not used it but it looks attractive
and I respect their product quality. They also offer a hand pump sprayer and
other related products. You can see them on their website.
You can use sand texture but I really
don't recommend it. It is very rough - a knuckle scraper - and it doesn't
look as nice as orange peel. For a long time that was the only way a novice
could texture, but those days are long gone.
For any texture, try it and if it doesn't
come out right, scrape it off right away and try again. Some
people talk of applying compound with a paint roller, but I have never done
that and I don't think I would be satisfied with the effect. I would expect
"pointy" bumps from it that would have to be sanded heavily. And mixing paint
with the texture will create a mess that you cannot correct. Not recommended!
Priming and Painting
You must prime raw drywall or patches
or texture or it will show through the paint. See the topic on
painting for more information on this.