Outer corners with plaster -- special corner bead?

amakarevic · 12-22-2012, 02:42 PM

I am in the last coat phase of my plaster restoration. Was wondering if there is something like a metal corner bead for drywall but for plaster. Or should i just use the regular drywall one?

Also, is using regular drywall tape for the inner corners OK or should I use something else? I wasn't able to find much help online for plaster work as it seems like an ever dying art. But so far it looks good, I applied the first two coats and just want to make sure the final coat looks immaculate.

Thanks -- see the photo attached -- at the top of the picture you can see where it meets with the old plaster.

Seattle2k · 12-22-2012, 08:48 PM

For inner corners, fiberglass mesh tape is often recommended for plaster work. I'm not sure what to do for outside corners.

drywallfinisher · 12-22-2012, 10:05 PM

are you trying to match up the top corner bead to the bottom? Plus finish the joints ...

This is how I would do it.
using a setting type joint compound (mix it up until it has a medium consistency) and using a 10" drywall knife.
Pull the mud from bottom to top PREFILLING the entire surface of both sides of the corner. Single motions from the floor up and ACROSS the top bead. Feather out the best you can and let it sit over night to set up fully. Be sure and take a smaller knife to prefill the joints as well before retiring.

This is a pain in the ass, but it's also the way it is done by professionals (me)

the next day: go shopping and this is very important. Lowes or Home Depot should sell a vinyl composite tape in a black box called Straight Flex. "do not buy a light weight version of Straight Flex" buy the original.

the wall repair: after scraping down the prefill coat, tape your joints with paper tape. not mesh
---grab your new Flex tape and measure out three pieces the height of your new bead.
1st piece is mudded FLAT on the right side of the corner....wiped tight to the very bottom of the top bead. 2nd repeat this process on the left side of the corner...wipe tight till bottom meets top''
at this point..take the 3rd piece and make a crease down the length of the tape...creating a corner...vinyl composite.
Mix up more quick set with the same consistency and cover the corner making the depth of the mud the height of the top bead...if that doesnt make sense look at the picture again and picture the fix in your head. You want the best depth that you can create near the joint..place the bead lightly into place to find what the give is on the mud. you HAVE to wipe the corner into place..pulling enough mud out from beneath the tape without smashing or creating deep edges ..this is important..
THIS IS WHAT I WOULD DO......BEFORE the mud in the bucket sets, pull the corner with mud, finishing it as if it were a normal bead up to a point above the top bead. just be careful of the shape of the mud in the bucket and to not smash what you have already created on the wall.
wait until the mud cures completely... NO MOISTURE
from this point on you're basically finishing a corner..with one or two more coats of regular joint compound you should be doing well.
Chances are good that there will be a little bump where the corners meet up, but being as you used the quick setting mud (2x) the strength in the corner is better than some might suspect and the joint shouldnt break or mud fall off.
this repair happens a lot from water damage in older inner city buildings

amakarevic · 12-28-2012, 06:00 PM

Quote:

Originally Posted by drywallfinisher

using a setting type joint compound (mix it up until it has a medium consistency) and using a 10" drywall knife.

Thanks. Does "setting type joint compound" mean hot drywall mud of different drying time (e.g. 5, 20, 90 etc) they sell in bags? I was thinking about that but was skeptical how it integrates with plaster (i mix 2.5 masonry sand to 1 hydrolic lime for inner coats and 1.5 fine silica san to 1 hydroli lime for the final, smooth coat).

drywallfinisher · 12-29-2012, 11:49 AM

it would be difficult to find a lime based plaster. There are places you can still find it in the NE...Virginia limeworks is my preference. They provide the majority of lime based plasters for restoration of historical buildings, re: the whitehouse, the Jefferson estate, ect..
quick set is the bag 5, 20, 45, 90, 120
for your job I would use a 45min quickset
the mud shouldnt have any adhesion problems at all.
the trickiest part of this application is aligning the straight-flex flat pieces to where they aim the creased flex right into the top bead. some finishers would condemn the use of a vinyl bead over metal. I get their argument but what use is strength if you have an obvious eye-sore. Besides if the bead gets beat up, sometime in the future, the fix to that would be a full metal bead from floor to ceiling...which is an easy fix
good luck

amakarevic · 12-29-2012, 02:22 PM

VA lime works is what I used.

I am somewhat confused about some of your instructions -- not sure if they pertain to outside or inside corners.

But let me tell you what i was thinking: As you can see in the pic, I have already applied the inner coats of coarse plaster and am ready for the final coat. For the outside corner, can I just take some quickset mud and put in on the inside of a metal corner bead and then fit the bid with the mud in into the base coat of plaster so that the mud acts as both the filler in between the final corner line as drawn by the bead and the adhesive for the bead? Once I fit it in, I scrape off the excess on both sides. Do you think that will work?

drywallfinisher · 12-29-2012, 08:36 PM

The way I explained it is the way I would do it. Including the materials I would use to finish it.