setting plasterboard

[floydus]

Need some help with plastering issues here, i have basically a 4 hipped roof at 12 degrees thats cut in using hardwood rafters. Its a raked ceiling with gyprock fixed to battens that are screwed to the underneath of the rafters.
Coming down the hips, i've cut the plasterboard to the angle, and its come up with a neat joint, the problem is with setting that joint.
The plasterboard company recommended a plastic strip that has a variable angle to fit into the joint, after its been sprayed with glue, but the thing will not stay put, even with staples every 100 mm or so it keeps bulging out.
Has anyone out there got any ideas on other products, keeping in mind that the angle we're talking is only about 3-4 degrees off flat.

[seriph1]

hi and welcome to the forum! You'll find a bunch of info and a lot of helpful people here ...... to your issue: I am having trouble getting my brain around what youre saying and am wondering if you could take a few pics of the offending area and post them? Also, I am wondering why the thing would bulge out too - seems like youve really slammed the sucker down with everything available, so is the plaster popping from behind? Maybe I am way off the mark and dunno what I am on about (nothing unusual there) ..... could you supply some more info?

have fun

[floydus]

Yeah thanks Steve, i thought my ramblings were going to be hard to follow, i'll get onto the picture and post it up.

[Ivan in Oz]

I was wondering about holding it in place with some 'light' timber along the length; with a couple of "G" clamps.
Wax or 'Release' the surface of the timber first so that it won't stick and pull the work undone.

[floydus]

Here's some pictures to clarify, and i should add that i have a plasterer doing all the setting, and he has'nt come across this particular situation.
The other option is to try bedding in paper tape, but he does'nt reckon the join will be real straight, which is kind of important.
Also, this is all new work, so the plasterboard is screwed firm to a continuos batten down either side of the hip.

[seriph1]

thoughts: get a thin metal mesh bent to the aproximate angle you need and screw it through the join into the battens, then put a skim coate of plaster over the whole lot. Two: place a decorative batten over the join, using a material that compliments. Three: a piece of bent metal again but this time it is stepped out from the ceiling and has concealed lighting in it that would play a wash of lioght out from it. four: ask more experienced plasterers, preferrably those who specialise in solid plastering.
Finally: if it was mine, (and without seeing the actual job) I would probably get some 2 or 3mm steel bent up to the correct angle, fixed through the centre line and paint it the same colour as the ceiling finish. It's all work no matter what you do, but if that line is going to continually open over time, polacing something stable on top of it may be the only way. I feel certain you and I will be the only ones who notice it after about a minute. :D

have fun

[BrisBen]

From what I can see you have a number of obtuse internal angles that you need/want to set

I know this sounds like a silly question but - what type of adhesive are you using

My guys use Trim Tex brand spray adhesive - which is made by the same company that makes the plastic beads

If you spray both surfaces and let it get a little tacky it can stick pretty well

If you want to go to metal internal angles so you can staple them (similar to those used on 90º externals) these can be carefully hand bent to suit

Try a specialist plastering supplies shop

Just out of curiosity - Why isn't the plasterer putting them on ?

[floydus]

Thanks for your thoughts guys, the glue is trim-tex, and seems to be good stuff, i think, however that the angle is just to shallow for the plastic bead, and its bending back on itself. I dont know if you know Coochiemudlo Island BrisBen, but its a pretty casual place, and getting trades over here is ....well, difficult.
Good place to live though.
Thanks again, this is a great help.

[seriph1]

I wonder if the memory in the plastic could be reset using heat? (still think metal will be the go though)

even I know coochie (ex-brissy boy here)

have fun

[ThePope]

I think the expanded metal angle used for external corners on plasterboard walls is your best bet. Is only very light guage and is easily bent to shape or in your case flattened out to suit the angle you've got.

If you measure back from the centre of the hip a distance that suits the width of one leg of the angle and snap a chalk line you'll be able to keep it nice and straight which is what you want.

[Pedal Harder]

Would this metal angle be able to be bent to suit a 45 degree external edge? What I have here is what was an eave that then meets the bottom edge of a skillion ceiling at about 22degrees. Not certain the gyprock sheets will meet perfectly to allow an easy join. Make sense? Cheers

[Guy]

The best stuff to use is the adhesive backed paper tape you get from the plater suppliers, you just fold it anglong the centre ( its scibed already) then place id a bucket of water. The place over the join and smooth over with a plactic trowel, once it is dry place a layer(thin) of finish coat and sand when dry.
Forget about the internal or external metal angles, this is the easiest way.
You can alsop use it on the internal 90 degree angles, but not the external where you are better off using the metal ones
Note : Bunnings sell the paper tape but does not have adhisive on it.

[Pedal Harder]

Thanks Guy - what if I need to 'pull' some edges into line - maybe the paper won't do this ? Any other options aside from the metal edge?

Cheers (picture now added - hope you can see what I mean?

[Guy]

On the circled area of your pic use a metal perforated type. That will give you the best results, but for the internal angles use the paper tape

[scooter]

Can get an obtuse perforated corner bead for angles > 90 degrees.


Cheers....................Sean

[rod@plasterbrok]

Another old thread that I think I could contibute to for the benefit of other readers.

OBTUSE INTERNAL ANGLES

Here are some options for obtuse internal angles, particulary in ceilings. I have listed them in order of preference.


Cut and fold the sheet to form the internal.
Use an obtuse metal internal angle.
Use flexi tape (a stiffened paper tape that folds to any angle)
Use paper tape.
Use a plastic angle that folds to fit any angle.Cut and fold

Cut and folding the sheet should always be tried first. Success will depend on how well you measure, straight you cut, or how straight the framing is. If the angle is not right when hung it is not a problem because the attempt itself will give you the best substrate for the other methods.

To cut and fold, cut along the back of the sheet at the right point, (you can use an offcut to check your measurement each end). The cut needs to be very straight. Glue along the framing members either side of the angle (don't be stingy on the glue). Hang the sheet by positioning the sheet along the lower join BEFORE alowing the sheet to snap. Fix a few spots along the lower join, then push the sheet up into the internal from the outer edge of the sheet. DON'T PRESS INTO THE INTERNAL. All pressure should come from the side. Nail off both edges of the sheets, do not nail the internal, keep nails at least 300mm back from the internal.

Sometimes you will find the face of the sheet will come away at each end. This is not a problem, just leave it until the glue has set, (provided that the rest of the angle has come up ok). Use a trimming knife and cut out the paper that has come away. I would only do this if it is no more than 300mm long. It is easy then to fix this with paper tape blending it in to the rest of the internal.

If the angle doesn't fit right, cut along the face of the internal and nail along each side. Just as you would have if you had hung 2 sheets.

Metal internal angle

Obtuse metal internals are factory made to 135 degrees. Only use these if they either fit right or you can make them fit. To fit right the edges should fit flat against the sheet each side. To make them fit, lay them on the floor and gently step along the anlge to either flatten it slighty or open it up slightly. THIS IS ONLY FOR MINOR CHANGES. I have used this method well many times, but I can see others getting into trouble with it, so if you can't get it to fit ok go to another method. Staples are the best fixing method. You may find you need to staple every 200mm or so if the angle is not fitting well. What happens is when you staple one side the pressure makes the other side lift. This is why the person using spray on adhesive had problems.

Flexi Paper Tape

If you can't get a metal angle to fit well, use flexi tape. Flexi tape works very well for short angles, say, up to 2.4m. They will come up straight 8 out of 10 times with no effort. However on longer runs, it takes a bit of experience to get them really straight. Not a problem though, I will tell you how to fix that. With Fleix tape, it's a good idea to fold the tape before hand roughly to the angle you wan't. It is applied like normal paper tape. Its stiffness takes out small imperfections and spans gaps well. If the gap in the internal is greater than 10mm I would suggest prefilling the gap, (remember to scrape back the prefill before it dries but after it has set). Use a second base coat on flexi tape and then a top coat.

If you just couldn't get it staight then here is how to fix it (see methods in Paper tape heading).

Paper Tape

Apply paper tape as usual, rarely will you get a straight angle fist up.
The paper tape is basically there to reinforce the angle not to get it straight.

There are 2 methods to straghten the angle after applying paper tape, (or flexi tape).

Flick a chaulk line along the center of the angle. This will show up the areas that need filling out. If it is only small areas that need filling out, then using the chaulk line as a guide fill along the line. Sometimes all thats needed to make an internal look great, is 300 to 600mm of filling along the lenght in one or 2 spots.

If it needs a lot of fill then screw a staight edge along the line, fill one side 2 coats of base coat. When set remove the straight edge and screw it to the other side fill that side the same. Remove the straight edge fill the screw holes, top coat both sides and you will have a perfectly straight angle.

Plastic angle

The least favored method by me. The reason is, most plastic angles on the market will leave a defined groove in the center of the internal, to me that just doesn't look as good as a nice clean finish.

Plastic angles are installed the same way as the metal angles. They can be difficult to keep straight. The other reason I don't like the plastic angles, is that, it take away the options described under paper tape to "fix" the angle if its not straight.

Hope this helps someone.

Rod Dyson

Plaster Brokers

P.S. we have more plastering tips on our web site.

[scooter]

Thanks for contributing, Rod. :)


Cheers...............Sean