Whenever you are
hanging plasterboard, you will run across some framing members that do not line
up perfectly with their neighbors. What, if anything, to do about it is very
subjective, and depends mostly on how willing you are to accept flaws. It is
natural to want walls and ceilings to be completely planar. As long as the
framing is wood, this is just not likely to happen. Wood framing comes from
living organisms and is made up of cells that will absorb and give off moisture
virtually for ever, even though the tree is long dead. As a result, lumber is
rarely perfectly straight and can and will move over time.
That said, what is the practical nature of how you will hang the plasterboard?
If you are using 1/2” board (the standard for residential construction), the
board is fairly flexible and it will bend from one stud or joist to the next.
If the framing is way out of line, this can show up in the finished wall. This
is especially true if there is a light source (window or overhead lighting)
that allows light to flow across the surface. One of the techniques used to
hide some of this is the application of texture to the finished wall.
Let’s get to what you can do to minimize the inconsistencies of the framing. If
a stud or joist is out of line by being set back from its neighbors, you can
shim it out. The problem is normally that the stud or joist has a “crown” and
the center of the span is out of line with the others in the wall or ceiling.
You can purchase cardboard shim strips (frequently called butt strips) that are
about 3 feet long and 1-1/2” wide. They can easily be stapled to the stud or
joist to build out the center. The plasterboard will span the small difference
between the wood and the step out to the shim without problem.
If the framing member is crowning into the room, you may need to remove some of
the wood. The easiest way is to shave it down with a power plane or a belt
sander with course grit belt. Keep in mind that this is “rough framing” and you
do not need to have a perfect surface to apply the wall board. You will be able
to spot any framing that is grossly out of line by sighting down the surface of
the wall or ceiling. Put your head in the framing so that you can look along
the future surface. A long straight edge should be used to check individual
locations when shimming or planning.
If you are using 5/8” plasterboard, it is much more rigid, and will be less
flexible in bending between miss-aligned studs or joists. Although this leads
to less obvious bulges and dips in the wall surface, it can be a problem when
nailing or screwing off the board. The screws will tend to rip through the
surface of the board or a hammer will tend to smash through the board when
attaching to a low spot.
Keep in mind that the wallboard is going to be “finished”. A talented
plasterboard finisher can hide a lot of inconsistencies in the surface. When
you are hanging the board, pay attention to the tapered edges, being sure to
place two tapered edges together, and avoiding placing tapered edges next to
door or window openings. Hang the ceiling first and then the walls. Run the
board on the walls horizontally, with the top board going up first. Offset the
butted ends of the sheets as you would with plywood sheathing or floor framing.
You should always offset at least two studs or joists.
You can precut any holes needed for electrical boxes, lights, plumbing or other
locations that require access into the wall. Professional plasterboard hangers
will usually just mark the center of electrical boxes on the board and then use
a special router to cut the hole after the board is at least partially attached
to the wall. Double-check before the board goes up to make sure you know where
all holes need to be. A complete set of photos before hand can save a lot of
anguish later when one of your electrical boxes has disappeared.