Hi, I've been reading through a lot of websites on veneer plaster
trying to decide if we should refinish the drywall under the paneling
in our house or replace it with blueboard. because of cost we are
looking at applying Plaster-Weld from Larsen products over the
drywall/paint/brick and then applying the Ivory product veneer plaster.
(both reccomended from a local supply store.)
I've contacted some of the local plaster professionals and they do this
commonly. I've also heard of this method being used a lot in the
I wanted to know of other's experience with doing this over regular
drywall, painted drywall and brick and find out what works the best,
things to watch out for and any other recomended product that I could
look in to.
At the advice of a professional, I have applied Larsen's over plain
drywall, and then used a 3/16" base coat of plaster and finally a 1/16"
veneer coat of finish plaster.
Plasters I used are from National Gypsum:
A lot of my use of this system is for patching up an old house that has
plaster over wood lath. Sometimes I will put in a drywall patch that
abuts some wood lath where the plaster has fallen off. I start by
using Larsen's on the drywall patch and on all of the exposed wood
lath. Then I do the basecoat plaster over the drywall and also over
the lath to create a smooth surface. Then I do the coat of finish
plaster over everything. Since the drywall is 1/2", and the plaster
wall is typically 3/4" thick, that accounts for 3/16" basecoat + 1/16"
finish coat over the drywall to be flush with the original plaster. In
your case, you could change the thickness of the basecoat, or eliminate
Surprizingly, blue board is not available in my area, however, the
veneer plasters that are to be used over blueboard are available. So
to get around this, that is why I just use the the bonding agent over
I have not used bonding agent and veneer plasters over brick or painted
surfaces, so I can't directly comment on that. However, in my limited
experience, it seems to me that it would be the right thing to do and I
would probably go ahead and do it if I found myself in that situation.
If you have never done real plaster before, practice on some scrap
drywall. It takes some practice to get the surface flat and smooth,
and to know how long to let the paster set up before going back over it
for final smoothing. It's different from applying regular drywall mud,
so even if you think you are good at that it still helps to practice
your pastering technique.
Ken, THANKS. That is EXACTLY what I was wondering about. I'm more
encouraged about taking this on now. I've been trying to find some
videos of veneer plaster application. I've found some small clips on
Bob Villa's Home Again website, but would like to see something more
Do you know of any videos or dvd that show veneer plaster application?
I've read that USG has some, but wasn't able to find them on their
Sorry, I don't know of any videos or anything. I'm trying to remember
how I learned what I know about plastering. I guess it was just a
combination of talking to a professional, reading some books and
websites, and just plain old trying it out and seeing what I did wrong.
I'll give you the condensed version of what I know:
Apply bonding agent with brush or roller, whichever is more convenient.
Allow to dry according to instructions, which I believe is something
like letting it dry at least until it appears dry to the touch. But
don't put it on too far in advance, because you are supposed to do you
plaster within a day or few days of application of the bonding agent.
If you are doing a base coat, mix it according to instructions, paying
attention to not mix it too long. You'll need a hawk to hold a
managable portion of plaster while you work, and then go ahead and
apply with a trowel. I got myself a good stainless steel trowel made
by Marshalltown (I think that's the name). Apply a blob of plaster to
the wall and while moving the trowel upward to press it onto the wall
while trying to keep the blob from falling off. Continue to spread
and trowel it until it is approching the final thinckness. Then
continue with the next blob and so on until you have covered the wall
section. Go back over it before it has started to set up to get the
thickness uniforn over the wall, and to make sure the surface is flat.
If it's just the base coat, don't worry about smooth, you actually want
a rough surface so the next coat will have something to grab on to.
For the basecoat, don't go back over it any more once it starts to set
up, you'll only make things worse, not better.
A day after the you do the basecoat, for the final finish coat, do most
things just as described above, except for the finish troweling. Once
the wall is covered, go back over it to get it as smooth and flat as
possible, but you will still have lines from the sharp edge of the
trowel. Don't worry about that just yet, leave those lines alone for
now. Just flat and relatively smooth is what you want for now. Now
wait until the finish coat of plaster starts to set up. This is the
part that I found hard to judge at first. You want it to be set up all
the way through to whole thickness of the finsh coat. The surface will
start to set up first and almost have a bit of a "crust" on it. Wait
until it is sets up all the way through the whole layer. While you are
waiting, spray dry spots with water to keep the whole wall moist. Not
running with water, but just moist. It is imperative that you keep it
from fdrying out before it cures. Remember, plaster needs to cure, not
dry just like concrete. If it dries, it results in "dead" plaster that
is uncured, and will just be dust that brushes off of the final wall.
But anyway, back to the final troweling. Once it has just set up, then
you need to go back over it with a lot of pressure and more water
sprayed on the finish coat. There is probably some word for this, but
I don't know what it is. At this point, you are working out all the
final surface roughness to get a smooth coat. I have found I need to
apply a lot of pressure and almost use the trowel as a scraper to scrap
down high spots. As you are doing this, the parts that get scraped off
will make a little bit of wet plaster build up on your trowel. This
little bit of wet plaster will fill in any low spots like those lines
from the sharp edge of the trowel. Just keep going over it until you
get the finish you desire. And if it starts to dry out, spray some
The key to this step is to time the curing just right. If you are
doing a large wall or a whole room, the first bit you do will be set up
enough before you finish applying paster to the rest of the wall, so
you will find yourself appling finish plaster to one section, going on
to the next section and applying more plaster, then going back to the
first section for final smoothing, then going on to the next section,
etc. It's a real game trying to time everything. I have found that
minutes count in the curing process, so make sure you have everything
you need all set out and ready to go with no interruptions. There is
no stopping to take a break in this kind of work. If you sit down for
10 minutes because you got tired, you may come back to find a batch of
plaster hardened into a big lump that you have to toss. Unless you are
just doing a small section of a few square feet, you will get tired, so
start fresh in the morning, don't do this at 10 o'clock at night.
I described using a base coat covered by a finish coat. If you don't
want to or don't need to use a base coat, then I think it's OK to skip
the base coat. But one thing to keep in mind is that the finish coat
of veneer plaster must be thin. So if you are going over bricks for
example, you may need a base coat just to bring everything to a level
surface and then apply the finsh coat over that.
So this is my experience with plastering. I'm no expert at it, I'm
just a DIYer who has fooled around enough that I think I have figured
out most of the important points. If you would like to do something
other than a smooth finish, I'm not sure how you would go about that.
I haven't done it. But I do know that I like the look of a nicely
finished plaster wall better than just drywall.
Ken, that is just GREAT. Thanks you for such a detailed overview of the
process. It's alot more than I was expected to find. I thought a bunch
of people would just tell me to have a professional do it or that I
couldn't do it over drywall and have it look good.
I really appreciate your help. Let me know if you come accross a video
or have any other suggestions! thanks again!!
Not exactly on topic, but maybe useful: Some years ago, we did some
veneer plaster - two coats, "Imperial" and "Diamond", over blueboard.
We had a problem with speed - even with relatively small batches, it
was setting up before I was finished trowelling it smooth. We tried
retarder; it might have helped, but it wasn't a magic bullet.
The final finish was acceptable (to us), except for some 'bubbles',
where the base coat pulled off the backing. We never found out what
caused that. We did wet the walls before applying the base, and the
blueboard was new (from the store, at least), and appeared clean.
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