Recently I installed 50+ 8'x4'x1/2" drywall boards in my basement. I wanted
to do ALL the work on my basement finishing project. I taped, mudded and
sanded all the joints and then primed everything with Gripper (Glidden,
excellent product). After top coating the results were excellent.
Question. The pros put a 1/16" skim of mud over all the board surfaces. Why
is this done? I did not do this because as a total amateur I do not have the
skills. I have done everything else (electrics, plumbing, studs, drop
ceilings, lighting, heating and ventilation, 25' wall of bookcases, media
center with built in fireplace, etc) but skimming is way beyond my skills
and you can't read books to figure out how to do it.
Why is a skim put onto drywall?
From "Fine Homebuilding"
"Compared to standard drywall and joint compound, skim-coat plaster has
greater impact and abrasion resistance, improved sound isolation, and
can be brought to a truer flat plane resulting in a virtually flawless
It's a local thing. Isn't done in California, because the ground moves all
the time, and we're forever repairing drywall cracks.
Here, there's typically a knockdown texture coating on drywall. Easier to
repair in, when you need to in a couple three years.
And here, usually no basements, either. Water table is pretty variable,
and there's not appreciable frost to account for, either, in many places.
Adaptable folks, humans.
:> Why is a skim put onto drywall?:> :> Peter.:>
: It's a local thing. Isn't done in California, because the ground moves all
: the time, and we're forever repairing drywall cracks.
Done here is Arizona, although we don't have earthquakes.
Drywall hangers will spec either a smooth skimcoat or a textured
one. The former is substantially more expensive than the latter.
And to me at least, textured is nicer looking (if it's a fine, not
really heavy, texture).
It's not necessary, but I find the look of plain painted drywall,
with no texture, to be kinda cheap looking.
-- Andy Barss
They skim coat plaster on blue board, which has a paper face intended for
skim coat plaster, but they generally don't skim coat drywall (Sheetrock)
per se. If you used drywall, taping the joints and hitting the screws is the
A skim coat is usually 1/16" thick joint compound applied over "drywall"
(Level 5 Finish).
"Veneered plaster" is a 1/8" of plaster applied over "blueboard".
From National Gypsum's web site:
"Level 5 finish is recommended for areas where severe lighting
conditions exist and areas that are to receive gloss, semi-gloss, enamel
or non-textured flat paints. Level 5 requires all the operations in
Level 4. Additionally, a thin skim coat of joint compound, or material
manufactured especially for this purpose, is applied to the entire
surface. (This definition is referenced to Terminology, Section II, Page
2 of GA-214 to make the description of "skim coat" clear to all.) The
surface is smooth and free from tool marks and ridges. Before final
decoration it's recommended that the prepared surface be coated with a
primer prior to the application of final finishes. The Level 5 finish is
required to achieve the highest degree of quality by providing a uniform
surface and minimizing the possibility of joint photographing and/or
fasteners "burning through" the final decoration."
I don't disagree... however in the context of his rock hanging in his
basement with lots of bookshelves etc., tape the joints and hit the screws
was the right process. Little if any direct sunlight happening in most
basements... If he'd been talking about his living room that would be a
Are you sure you're not talking about a veneer plaster (aka skim-coat
plaster)? It is troweled onto blueboard, which is similar to normal
Skimcoating _is_ also done with drywall in places where you need a
higher quality finish. The drywall paper and the mud have different
surface properties (texture and absorption) which can be visible in the
finished wall in some circumstances, most notably with extreme lighting
and/or higher gloss paints. This is known as telegraphing or banding. A
skim coat helps even out the surface differences. It also protects the
paper from fuzzing during sanding, which is a common problem for DIYers.
The skim coat is just thick enough to cover, not a full 1/16", so it is
probably not beyond your abilities if you were able to mud the basement
yourself. For future reference, they do sell a pre-skimmed wallboard.
I thin the mud and roll it on with a paint roller. Then I scrape it off
with a wide knife. The mud left behind is very thin, too thin to measure
thickness. This thin coat makes the wall surface uniform and ready for
paint. I only do this when I want a smooth surface with no texture. If
this is not done the sheetrock has a different surface than the seams and
this can show thru the paint.
I prime, sand the primer with a fine drywall screen equipped pole sander,
and then reprime to deal with the variance between the joint compound and
the drywall paper. I heard about this from a guy who did high end finish
work in NYC. He suggested it as a way to deal with a really crappy rock and
tape job that I inherited where the guys had scuffed the paper all over the
place when they sanded it... It worked so good on that repair job that it
became my standard process when the job had to look good. I found that the
primer rolls on quick and dries quick compared to a joint compound skim job.
Some pros did mine and they SPRAYED the finish on. The particular product
was to have an elasiticity better than some others available (FWIW Rucoat
Equalizer). That was to avoid hairline cracking.
Afterwards, I took a drywall sander to level and then applied my paint
directly. NOVA notes that primer should be used and his reply has more info
than I knew - thanks NOVA.
Whether your lighting requires it or not is up to you. Let me say this much,
it's a beautiful finish. I've got expansive walls, ceilings, skylights,
large windows, and a tray - you don't see a thing but surface! The cost was
something like $500 extra (might have been less) for the whole house - an
advantage of being your own contractor probably. Sorta like going from R30
to R38, and insulating the whole garage, and insulating every wall in the
house, was only a few hundred dollars extra when I negotiated directly with
BTW I'm still finishing the downstairs so I'll be where you are soon again.
The way I laid out my shop electrical would have cost me a fortune if an
electrical contractor had done it.
There was a time that I was a pro. I (we) never skim coated rock. You may
be thinking of plaster. We (I) would 'skim coat' blue board, but we applied
at least two coats and the finished thickness was probably an eighth inch
or a bit more.
Don't know. Hung quite a few sheets in my time and never thought to do a
skim coat (don't think I could, know I do not have the patience!).
But, for shops, I would install plywood above the bench height for a secure
nailing/screwing surface and use drywall for the ceiling and get a cheap
spatter/texture gun from Harbor Freight ($17) and texture the heck out of
it. before primer and paint. I finished mine with a high-gloss Latex enamel
that reflects lots of light.
BTW - a recent sale at Lowes called my attention to the (apparent) fact that
OSB can be had for about half the price of Sheet rock! Bitch if you're doing
a living room, but a God send if you're walling in a shop!
Never seen new drywall skimmed, myself, but I've done it more than a
few times to repair pitted walls or cover orange peel or sand texture.
Sometimes, it's the only way to get a decent surface short of gutting
everything and starting over.
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