butt joint first coat

[emptybucketman]

Hi All,

I'm about to butt joint villaboard and I'm following Rod's site http://www.how2plaster.com/tapejoin.html

There is one thing that I'm not entirely sure about and seek clarification. When applying the first coat do I attempt to put base coat over the top of the tape or just concentrate on the building up the side of the tape. Moreover, is it a problem if I don't fully coat the top of the paper tape on the first coat.

[rod@plasterbrok]

Yes you will put a very thin coat over the tape, pretty much just enough to wet the tape with plaster. This helps to squeeze any excess from under the tape.

Then fill out either side away from the tape. Each coat is pretty much the same you dont want to have a build up of material over the tape, the tape should only just be covered with plaster.

Just be carefull when sanding that you dont sand down to far and hit the tape.

The final coat should be 300 mm wide each side of the tape, this will give you the best chance of the butt joint not showing after painting.

Cheers Rod

[emptybucketman]

Thanks Rod,

Keep adding to your youtube how-to plaster video library. I, like many, have found them a valuable resource.

[rod@plasterbrok]

Thanks, I am having trouble finding the time at the moment.

Cheers Rod

[emptybucketman]

Rod, as an aside, what should be the consistency of the base coat? I see that you recommend "wet" but I seem to make it too stiff and thus it is hard to work out from under the tape.

[autogenous]

Would you say toothpaste consistency Rod ?

*runs over to rods website link*

[rod@plasterbrok]

Hmm. "Wet" is how I describe it because because thats how I see it. A dry mix is still wet I guess, Hmm I'm confusing myself here!!

Would stiff and sloppy be a better way of describing it??

A good mix is not sloppy but not stiff!! really confused??

I guess really thinking about how to describe how thick a mix for taping should be, is not that easy. For taping try standing the joint knife up in the mix if it just falls straight over its too sloppy, if it just gradually falls over its ok. If it just stands up its too thick (dry). For second coating it should be just a little bit thicker than taping.

Does this help??

Cheers Rod

BTW just a side note on Villaboard, it soaks the water out of the mix much quicker than plasterboard. Therefore apply the plaster for taping a bit thicker and more consistently than you would for plasterboard to avoid dry spots under the tape, resulting in bubbles. Although I have never had to do this but dampening the join with a damp sponge first would help with this.

[Ronaldo451]

Quick question, Rod.

Is it OK to soak the tape in water prior to using it? On previous posts the main drama with tape seemed to be possible bubbling as the mud dries. To conteract that I cut the tape to length and let it soak for a few minutes, smeared the joint with mud, applied the wet tape and smoothed in with a spatula to remove excess water and then smoothed over with another smear of mud. None of the joins done this way has had any bubbling or cracks...

[rod@plasterbrok]

There are only a few reasons a bubble will occur under paper tape and all are due to the tape not making contact with wet plaster.

The first is that the plaster either was not there in the first place and the second that the plaster that was there had dried before the tape was applied and that the tape was not bedded properly into the tape.

Wetting the tape will not assist in the first two but may assist slightly in the last.

Having said that it will not do any harm either, it just makes it harder to work with.
Normally if we have a roll of paper tape that get wet we toss it out, because it is harder to work with.

Another type of "bubble" in paper tape occurs when the joint is open and although full contact with the tape is made it tends to "fall out" of the joint. It cant be scraped back only filled over or cut out. This is bad on butt joints as it cant be filled over without over filling the butt joint. To avoid this pre fill any gaps over 2-3mm and let it set and scrape back.

Where you do prefill it is worth noting that the pre fill will absorb the moisture from the taping mix as explained above for villaboard. Therefore you would need either be quick bedding the tape or put a bit thicker coat of plaster on this area prior to bedding the tape.

Cheers Rod

[emptybucketman]

Alas, I had a few problems with the butt jointing and was wondering what are the common remedies for the following?

1) protruding bulge under the tape corresponding to where the gap between the boards was greater than a few millimetres. I'm not sure whether to grind out the join and re-set it or build up the sides?

2) few minor bubbles - I plan to cut them out with the stanley knife and re-top with base coat

3) nicked tape when scrapping back - I plan to sand and re-top with base coat

[rod@plasterbrok]

The nicked tape makes it fury which swells when it gets wet. To fix this use the rounded end of the joint knife and push the loose bit of paper in, then trowel over.

Cutting out the bubbles is the way to go.

The protuding bulge could have been avoided by prefilling the gap! If its not too bad you can trowel it out by trowling the butt joint wider than usual I would start with a 10" joint knife straight down the center of the join, apply a coat that is level with the bulge and is flat for the full width on the joint knife. Do not feather out the edges of this coat. It is there to form a flat base for you to then trowel out either side away from that flat base, do the same again along each side with the blade edge running along the center using that flat coat as a screed this next coat. Do not feather the outer edge of this coat either. Now for the full width of the blade trowel down each side using the outer edge of the 2nd coat as you screed feather the outer edge of this coat.

Now you can apply a very thin coat of base coat over the entire join, work from the center and out to the outer edge in a circular motion. Use just enough mix to allow the blade to fill any depressions. Do the same with a top coat.

Now if you can follow that, you will have a very flat butt join, bulge not withstanding. I know I can picture myself doing what I have described however it is much harder to explain in words.

Hope you get it right.

It is much easier to trowel it out like this than ripping out tapes and scraping back the bulge flat and start taping again, which really is the only other alternative.

Cheers Rod.

[emptybucketman]

many thanks Rod,

The bulge is on the bottom last metre of the wall and gradually gets worse. What's the best way to remove the tape? Do I just dig it out with a blade?

[emptybucketman]

Hi All,

Is it necessary to plaster the internal angle between the ceiling and the wall, if I'm going to install a cove cornice?

[rod@plasterbrok]

No

Sorry I answered your post above last night but it hasnt come up?

Just lift with a knife and peel away what you can, dampening it down may help a bit. use a sharp tool to scrape out all remnants of tape and execc plaster. Scrape out the groove about 5mm wider than the tape to assit with bedding the new tape.

Cheers Rod

[emptybucketman]

Hi Rod,

I decided to follow your previous instructions and widen the join. But thanks for the tip on removing the plaster. The sad thing is that I'm running out of things to plaster just when I'm getting the hang of it.