Master of Plaster Q&A

MOP on bathroom ceiling

Brian Dillon — Fri, 21 Aug 2009 19:39:01 GMT

Hi,

I've read the other messages that talk about using a mix of portland cement with the basecoat as the first layer, but am wondering if that applies for using MOP to patch on a bathroom ceiling.

I have a sad tale of a homeowner plumbing repair gone awry. To make a long story short, I had a good amount of clean water flow from upstairs through the first floor bathroom into the basement. All of the paint separated from the underlying plaster, but as near as I can tell, everything is still solid. The ceiling had a layer of what appears to be muslin cloth beneath the paint which I removed. I'll be using a stripper on the plaster to remove what paint residue is left to give myself a good work surface.

The plaster is in mostly good shape...a few cracks that I will use mesh tape to bridge. There is one spot where there is a piece of green board along with joint compound that I will be replacing due to the water damage. From what I have read, I can put in the green board, use mesh tape, and then coat with basecoat/finishcoat?

Thanks in advance, and this forum has been a real lifesaver!

Brian

Silly question from a homeowner

Brian Dillon — Fri, 07 Aug 2009 00:08:18 GMT

How in the world do I open that 5 gallon bucket?

I told you it was silly.

Brian

A computer guy, not a plasterer :-)

Getting the product ??

S.Lyle — Sat, 13 Jun 2009 19:24:35 GMT

I came across this site while trying to figure out how to repair my plaster walls.

I have a house built in 1915 with plaster using a wood lathe. I have many cracks n the walls and in some areas I have had to remove the plaster from the lathe. The largest of the removed areas is approx 1' x 2'.

The plaster appears to have a wood fiber in it and it has a bumpy finish (sorry for the lack of description) to it.

I am wondering if I can skim coat it with MOP, and what product should I use to repair the areas that I have had to remove the plaster from.

The other issue I am having is actually getting someone on the phone at the numbers listed for MOP. I do have the changed number also.

Any help or ideas would be greatly appreciated.

M.O.P. over new drywall -- taping joints

Jim Burkhard — Mon, 08 Dec 2008 20:03:34 GMT

I'm in the middle of re-drywalling a kitchen (5/8" firecode) and was planning to again use Master of Plaster for skim coating when I am done. I've done this many times in the past (for 10 years now!) over *old* work (existing walls, both plaster and drywall) and new plaster (Structolite) and it's always came out great and lasted well. This time it's a little different in that I'm putting up NEW drywall and will be taping all those joints.

I see in the Master of Plaster instructions that they tell you to tape the joints & screws holes with mesh tape and bring everything to level with M.O.P. base coat first prior to overall skimming with M.O.P. basecoat again.

I'm wondering if it is *instead* permissable to tape the joints with conventional joint compound and when finished use M.O.P. base + finish for the OVERALL skim finishing of each wall? I wouldn't bother sanding the joint compound prior to this, since the final step will be to skim the whole wall with M.O.P. anyhow.

I ask for 2 reasons:
1. The joint compound is a good bit cheaper than M.O.P. I'd go through a lot of M.O.P. just bringing all the tapered joints to level. It seems like a waste of really good M.O.P for this part of the job...
2. While I wouldn't want to skim a whole wall with it, joint compound is pretty well proven for use on drywall *joints* and that's all these are really. If M.O.P. does fine resurfacing old drywall (which was been taped with conventional joint compound years earlier), why not over new construction that has also been taped with normal joint compound?

If this is a bad idea, please explain why.

Thanks very much!
Jim Burkhard

Plaster repairs and cracked corners

Alexbenjm — Mon, 08 Dec 2008 19:38:20 GMT

Hello, I came across this website when researching how to repair and skim plaster walls. I am currently cleaning and restoring my first room in my 1923 house. I've taken off the layers of wallpaper and paint to reveal blue-green pigmented plaster walls. I've identified the pigment as calcimine. A TSP solution easily took care of that.

The exposed plaster walls are rather rough textured, but in overall excellent condition with visible trowel marks along with usual holes, gouges, and cracks from 80+ years of life. There are two large holes with lath exposed underneath the windows where I've removed badly cracked plaster due to moisture. I will be stabilizing the plaster first then I plan to use Structo-lite to patch up those holes, but should I use a bonding agent? Would a mesh be recommended for those two holes?

Should I use mesh for every single crack, no matter how fine? I've come across people saying one should apply mesh to the entire wall, is that a good idea?

One issue I'm trying to figure out how to repair are the corners of the room which are extensively cracked. I can see all the way inside the corners and see lath. What would be the best way to repair those corners? I'm thinking the corners should have some flexibility to accommodate seasonal movements of the individual walls and ceiling.

Eventually after all the repairs are made, I intend to skim using master of plaster. One last question, the glasslike polished finish sounds quite attractive but would paint bond to that kind of finish well?

Thanks!

new plaster falling off

martin jackson — Sun, 07 Dec 2008 16:53:18 GMT

hi guys i am a plasterer and recently done a local renevation job on a bungalow all walls and cielings were half moon artex and were very old and yellow as it was a smokers house and had not been painted for a very long time all walls and ceilings were sound so i cleaned most of the tar off pva glued them thistle bonding them then pva again and then plaster using multi finish. everything was ok all dried ok the painter has painted all rooms and in 2 rooms the plaster and bonding has fell off in sheets i do not want to repair until i know the cause as i have been plastering for 10 years and have never seen this happen before any advice would be good thanks.

Structolite

James — Sun, 30 Nov 2008 00:56:30 GMT

I would like to use Structolite to plaster interior walls. Since this is new construction is there a Gypsum product on the market that can be used that the structolite would receive?

creating new inside corners

liz — Sun, 31 Aug 2008 20:55:09 GMT

Kevin,
Doug has chipped away all the old plaster and it completely took away the inside corner! I know we have to build up with the structo but when we get to the point of finishing, is there something we can use to get a nice clean corner? I have seen those plastic inside out for edges. What do you think?

Water Damage to Exterior Wall

Sara — Thur, 03 Jul 2008 18:01:46 GMT

I just moved into my first home and after taking down what was left of the draperies, I found a nice 12x6 inch patch of plaster on an exterior wall that had water damage from a leaky roof (oh and there's a spot to match on the ceiling). As soon as I touched the plaster it fell off in chunks, and I'm pretty sure it had started growing mold as well.
I have removed the plaster that was damaged on the exterior wall (it's a masonry wall) to let the wall dry out... I've seen a lot about patching interior walls, but is there anything special to consider when dealing with an exterior masonry wall? It looks like the water also loosened some of the mortar between the bricks... so I suppose I have to deal with that too.
I'm hesisitant to take down the plaster on the ceiling but I'm afraid this has started growing mold as well... Any tips for working on the ceiling? The house is about 65 years old, so will I find lath underneath or...?

Thank You!

repairing bubbled plaster

pete freed — Mon, 16 Jun 2008 19:55:14 GMT

i'm getting ready to repaint for my daughter's in laws. around 2 of the living room windows moisture seepage(since repaired) caused the plaster on lath
to bubble. how do i repair it?? it looks like i could sand the surface smooth,finish with sparkling and paint. but i hate to experiment in this situation.

sealing MOP

cleta — Mon, 09 Jun 2008 21:08:38 GMT

I think I need to seal my final finish coat in the stairwell and hallway - lots of nicks and dings are bound to happen with people carrying stuff in and out. What is the best sealer that will make the finish coat rock hard?

Have thought about brushing a wash of casein binder over the finish as I know casein and lime are very compatible and the casein would help to harden the surface.

Whatever I use, how long do I need to wait before applying it? Do I have to wait for a full cure on the lime plaster or can I coat it like 3 days after it's dry?

Caenstone durability

Steve O — Mon, 02 Jun 2008 23:24:11 GMT

Curious on the durability of Caenstone? I have my sample created but am not to happy on how it easily brushes off with the faintest wipe of the finish. Is there a way to make it harder?

Thanks.

Still working with MOP

Steve O — Fri, 16 May 2008 01:22:11 GMT

Hey all, great forum. I have experience with 2 other Italian plaster manufacturers and MOP is different from both, especially the venetian plaster. In the italian plasters you use the same plaster for all three steps.

Now MOP requires two base, then the finish over that. I have noticed a considerable ammount of drag lines and chatter whenever I do the second base coat. I thought it was self leveling. The chatter is showing through the finish. What do you do to get rid of the chatter?

cracked plaster in new ceiling

nate — Thur, 27 Mar 2008 02:49:51 GMT

A ceiling I just had plastered had 17 cracks in it a few days after it was done. The walls had some too. My plasterer insists it was movement. There was a steel beam put in to replace the bearing wall in the middle of the room. He saids it's settling. There is no evidence of any movement o setlting at the two point loads and the beam was oversized and just as strong as the wall it replaced. Also the ceiling cracked in other areas that weren't affected by the beam and the walls cracked that were existing studs and had nowhere to shrk. He stated early on that his mixes has set up very quick and he was dry before he left (he said that was unusual) He now states that because I put a second layer of strapping perpendicular to the original layer that that was the problem.

Help me please.

nate

caulking before applying MOP?

cleta — Wed, 27 Feb 2008 17:42:23 GMT

Is this necessary? I was reading about this on a forum...someone doing VP and going back later to caulk between the wall and trim. I did not do this on my walls (didn't even know about it). The walls/trim are old and there are gaps between them in places, but I haven't had a difficult time getting a very clean line between the wall and trim...I just smoosh a little more MOP into any gap area. I figure that is one of the qualities of lime plaster, right? - i.e., that it is a great self-filler.

So - am I missing something? will there be problems down the road because I didn't caulk between the wall and trim? I looked through the MOP/VP instructions again and didn't see this mentioned in the prep steps. And I haven't heard of it being required with any other plaster, either.