setting plasterboard

[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