Trivia du jour - plasterboard

[Bob Mannix]

When I were young, I assumed that one plastered the dark side of plasterboard and used the ivory side if you weren't skimming (note I said "assumed", 'assumption is the mother of all c*ck-ups' etc...). As I matured I came to the conclusion you could skim either side but used to skim the dark side still.

I note now that manufacturers carefully stamp "plaster other side only" on the dark side (ie you must use the ivory side).

Don't really want a huge flame of indignation (but it is uk.d-i-y, that's kind of a given :o) ). Two questions:

1. Have I been wrong all this time?
2. What is the *manufacturer's* reason for insisting you plaster the ivory side?

[Rod]

Yes - you have. (But so was I.)

The plaster within is guaranteed to be hard up aginst the white paper. (I think it must be on the bottom when they make it.) There can be air bubbles, etc. just inside the dark side. (Cue Pink Floyd.) You also get the turnover bits on that side - so absorbancy will vary across the sheet and be least (I think) nearest the board edges. There might be a difference in the actual paper/card layer which is significant - but I don't know.

Saw a film about plasterboard making - maybe one utube or somewhere?

[Andy Wade]

I disagree. It *definitely* used to be the case that the grey side was for skimming and the ivory side for painting or papering directly.

Why it's changed I have no idea.

[Rod]

I agree that is what I was told (a long time ago), but I have come to suspect that I have always been wrong.

My earlier point about double-layer of paper is picked up in this Q&A from BG's site:

Q: Can British Gypsum clarify their position regarding the skimming of Gyproc plasterboard?

A: Skimming should be carried out on the front of the board (ie. the face with no paper overlap). In the case of Gyproc Wallboard this is the ivory face. This advice also applies to Fireline, SoundBloc and Duraline.

But I was never trained and didn't research then - it was just what I picked up from friends and acquaintances. So the argument/advice might indeed have turned upside down over the years.

[Bob Mannix]

Can you honestly remember where you read it or who it was who told you and what authority *they* had? I only ask because I used to think like you but, when it came to it, I couldn't prove to myself I hadn't just assumed it!

[Phil L]

One side of the board is completely wrapped in paper, that is to say, two sheets of paper are used to make the board and one of them (the one that should be plastered) is wider than the other, so that it covers one side completely and goes around each edge and onto the opposite side by about an inch. Then the backing paper is stuck on after, to form the other side of the board, and also to cover the edges of the paper that we've just mentioned.

In theory, if you plastered the backing paper, it /could/ peel away from the body of the plasterboard because it's only held in place by the plaster within the board, in reality this is probably never going to happen, unless it gets *really* steamy, perhaps in a bathroom or kitchen that is in use almost constantly.

[Bob Mannix]

Thanks you. That's both believable and sensible! Was this always the method of construction or was the failure mode ignored until now?

[dennis]

The plaster board I used last had the words plaster this side on it, but I can't recall the colour.

[Andrew Gabriel]

No - it changed about 25 years ago when we started importing significant amounts of plasterboard, and the UK had been at odds with the rest of the world. (This was covered on my plastering course.)

Ivory side is quality controlled with regards to absorbency, to give consistent results when plastered (or painted). Brown side isn't and different boards might behave differently.