Veneer Plaster Questions

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  #1  
Old 04-28-09, 11:43 AM
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Veneer Plaster Questions

Hello,

Nice forum here, I have reading extensively about plastering and more specifically blueboard and veneer plastering. The information on the interwebs is varied, even the information that USG supplies is varied. So I have a few questions and I suspect tightcoat or someone else on here could help me out. I recently removed a non load bearing wall that was located between my kitchen and dining room. I framed a compound radius arch that fit into the opening and matched another arch that frames the opening from the dining room to the living room. The arch was covered with blueboard on the wall sides and inch drywall on the interior of the arch. The drywall was installed brown side out and painted with plaster bonder. The existing plaster is gypsum lath with a base and veneer coat. It too was painted with plaster bonder. The total thickness of the existing gypsum and plaster is about (The house was built in 1942). Anyway, I put a basecoat of USG diamond basecoat that varied in thickness from to 1/8. I did it last Wednesday evening and ran out off steam at about midnight, unable to complete the planned 1/16 USG imperial finish coat of plaster. The plan was to use the base coat to bring the new construction to the same thickness as the old construction, then use the veneer finish coat over everything. It is unclear how to apply the finish coat now. Should I just spray down the base coat before applying the finish coat? Or should I plaster bond the base coat? Note in the second photo, the plaster is still setting. Now it is dry, very hard and completely white. The first photo shows the arch before plastering. Also does anyone recommend using the plaster retarders? Do they really affect the strength of the plaster that much? I was plastering like a madman in order to get it all on the wall and troweled to a decent finish before it set. It is difficult to tell from the photos, but I gave the plaster a brushed finish to improve the bond.

Before plastering:
<a href="http://www.flickr.com/photos/[email protected]/3484074306/" title="arch before plastering by av43050, on Flickr"><img src="http://farm4.static.flickr.com/3576/3484074306_fc94bd4965.jpg" width="500" height="375" alt="arch before plastering" /></a>

After plastering:
<a href="http://www.flickr.com/photos/[email protected]/3484074210/" title="plastered arch by av43050, on Flickr"><img src="http://farm4.static.flickr.com/3365/3484074210_6b53d315cf.jpg" width="500" height="375" alt="plastered arch" /></a>
 
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  #2  
Old 04-28-09, 04:44 PM
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Why did you not plaster all the way to the ceiling?

There is no need to wet anything down except to kill some of the suction but you run the risk of the Plaster Weld letting loose if you do that.

I am more worried about the difference in suction between what you plastered and what you didn't.
 
  #3  
Old 04-28-09, 06:24 PM
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I intended to only use the basecoat on the new sections and not any of the old. That way the way thickness would be consistent. I smeared a little over onto the old plasterwork when I was troweling the base coat in. I know I should have continued plastering with the imperial (covering the entire wall surface) before the diamond dried completely, but I ran out time that evening, as I had to get up up very early the next day. I am just trying figure out the best way to finish this wall. I am not too worried about the bonder on the old work, I can shield it when I spray the basecoat. I am going to put another coat of the bonder down anyway, the instructions for it say I should reapply after it sits on the wall for more than 10 days. But then again I will not spray if you do not think it is necessary, I just thought it may dry out the imperial before it sets.
 
  #4  
Old 04-29-09, 08:43 AM
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Diamond basecoat? Do you mean Imperial?
Imperial Finish? Do you mean Diamond?

If you are using Imperial Finish I think you don't have to worry about it drying out before it sets.

No matter which finish, I think this is what I would do. To even out the suction on the whole area I would paint it with the Plaster Weld. That way the suction on the unplastered and the plastered areas should be closer to even.
Now I think you might have a little trouble with the Finish sliding around on the unplastered area. That is why you should have plastered it. But try this: (I've never done this mind you but I think it will work.) Put a tight coat of your finish over all the area work quickly. Then just as it sets double it up with another coat of finish and lay it down nice ans smooth, double that up and trowel it smooth use only enough water to keep it lubricated.

Let us know how it works and take some more pictures after you are finished.
 
  #5  
Old 04-29-09, 03:28 PM
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"Diamond basecoat? Do you mean Imperial?
Imperial Finish? Do you mean Diamond?"

No, I bought diamond base coat and imperial finish because that all the local supplier carries and the USG website indicates they are compatible. Why would the plaster slide around on the bonded unplastered surface? The diamond did not. Is imperial harder to work with? Anyway thanks for your help,
I will paint everything with the bonder tomorrow night. I am taking Friday off to do the finish coat.
 
  #6  
Old 04-29-09, 04:33 PM
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Sure enough. I didn't know there is a Diamond base coat.
Is your Imperial smooth? If so that is why it will want to slide. if it is sanded (and I haven't looked to see if USG has sanded Imperial) then it will grab a little and you will have no problem.
That is the only reason I am concerned about sliding.

I think you will get along fine. Don't be tempted to mix the Imperial too stiff. You want about the consistency of butter that has stood at room temperature for several hours. It will not spread like butter but maybe more like peanut butter. Spread on a coat and double right back leaving it almost perfect then go over it yet again to fill in imperfections then trowel it through it's set with enough water to keep the trowel and plaster lubricated and clean the trowel once in a while but not so often that you waste the fat that comes to the surface and stays on the trowel. That is what gives the plaster its polish and fills in all the imperfections.

Did you apply some tape between the new and the old work?
 
  #7  
Old 04-29-09, 05:45 PM
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Yes, I taped. You can sort of see the tape in the before photo. The bag of imperial I have says it is 25% silica sand, but it does not say what the gradation of the sand is. Thanks again for your help.
 
  #8  
Old 05-04-09, 01:35 PM
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The imperial was definitely harder to work with. There are several areas of "blemishes" that I did could not trowel out before it set. The temperature was a warmer than I anticipated, so my working time was only about 45 min/batch. Next time I do this, I will definitely have a helper. I am now try to decide if the blemishes are enough to warrant another coat. Also, several small hairline fractures have appeared. They are small enough that they do not really show on camera. Any advice on how to treat those? Anyway, here are the photos:

Painted with the bonder
<a href="http://www.flickr.com/photos/[email protected]/3501433635/" title="Arch with plaster bonder after base coat by av43050, on Flickr"><img src="http://farm4.static.flickr.com/3587/3501433635_09282d4c36_o.jpg" width="1024" height="768" alt="Arch with plaster bonder after base coat" /></a>

After the finish coat of plaster:
<a href="http://www.flickr.com/photos/[email protected]/3501433715/" title="Finished? Arch by av43050, on Flickr"><img src="http://farm4.static.flickr.com/3412/3501433715_3716a78c5a_o.jpg" width="1024" height="768" alt="Finished? Arch" /></a>
 
  #9  
Old 05-04-09, 08:30 PM
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It's hard to give a smooth finish another coat.
If the blemishes bother you try some joint compound and sand very carefully and not too much. It will take the glaze off the plaster if you sand too much.

I don't know about the cracks. You might try scraping them off. Sometimes when the finish is not bonded well it will crack like that. If it doesn't scrape off then it is well bonded and paint might fill the cracks.
 
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