Skimcoat is a generic term used by plasterers and tapers (drywall finishers) alike. Don't be mislead by builders offering skimcoat as
a finish if you're actually looking for veneer plaster. There is a world of difference between the two.
The base (wallboard) is the beginning. Both systems use this gypsum cored board which is covered with paper.
For plaster the paper is treated to allow for absorbtion of water (suction) in the application process. It is also colored a bluish
gray similar to this background hence the name BLUEBOARD. Other types of board are colored green or purple for identification purposes. These are
moisture resistant (not waterproof) sheets that can be finished with joint compound in the same manner as typical drywall.
Veneer plaster over blueboard is an application of gypsum plaster over the entire surface of the walls or ceilings. There are
different product types available depending on the overall hardness desired. The most common are extremely fine and creamy
when mixed. When polished and hard, in about an hour, they offer a mirror-like surface ready for paint {or not, depending on
your liking}.My personal preference is a special finishing plaster that contains a fine sand aggregate. It requires a bit more
work to smooth trowel but the end result is a hardness twice that of the other type.
Another which also fits into the skimcoat category being that it too is just one coat over blueboard is a basecoat plaster
troweled flat(not polished) or texture finished. This product is actually intended as a first coat in a 2 coat system.
Any of these veneers have the benefit of being a durable, abrasion resistant surface which means less nicks and dents in the wallboard
during construction and for the life of the wall.
Skimcoat as in drywall is a coat of thinned down joint compound which is applied in many different ways to the entire surface
which eliminates the texture difference between the paper and the initial joint compound finish used on just the fasteners and
joints. When painted it is very difficult to see the difference between this and plaster but here is the problem. The best drywall
job is still only DRYWALL. This soft, very thin coat offers very little abrasion resistance and when hit or scratched will bring
you right down to the paper or worse. In time, usually the first year, as the new construction begins to settle, studs twist
taking the fasteners with them. This is the major cause of nail popping or bulging. Joint compound is merely a filler whereas
plaster forms a bridge over the fasteners. When the stud twists, the screwhead will more than likely just pull away leaving the
surface unharmed. Speaking of fillers, what you see below is an angled ceiling/wall joint that was, first of all, not
filled properly, and when the building settled the paper tape simply wrinkled having nothing behind it to hold onto. The repair
would mean cutting out the old tape, filling the gap and refinishing. With plaster, this joint would have been initially taped
with a mesh and plaster would have completely encapsulated it. Even with settling the most that would happen is a small
easily repaired crack.
