Joint Compound or Multifinish on taped joints?

[Rich]

Hello,

I am planning on jointing plasterboard with tape (paper) and using multifinish instead of jointing compound. I will then be skimming the whole lot with multifinish.

What i have read abount joint compound and taping usually results in the surface just being sanded and painted. i.e. No skimming.

So i am assuming that multifinish would be ok. It's just a pain in the ass to use two different types. With mulitfinish i can just joint and skim in one batch.

I will use joint compound if someone tells me that i need to...

Regards,

Rich

[Andrew Gabriel]

In that case, you should use scrim tape, not paper tape. Scrim is netting tape which allows the plaster to pass though and bond to the board under the tape.

[Rich]

The reason i wasn't using scrim tape is because there are a few 'gaps' where the plasterboard meets on internal corners. I want to use the tape to bridge the gaps and produce a clean edge.

I don't think there is a problem using paper tape in this way.

Regards, Rich

[ben]

I also think you should use scrim tape, rather than paper. The `gaps' on internal corners will be filled just fine using multifinish alone, assuming they aren't more than say, 5mm.

It's a bit tricky to get neat corners without a corner trowel anyway, so you might have to do some filling afterwards.

Ben.

[Andrew Gabriel]

In this case you should use bonding coat to force through the gaps so it oozes through and out the back first. This will bond the plasterboard together. Then use multifinish or plasterboard finish with scrim over that.

I think it will pull away from the board first time there's any relative movement between the two (someone leans on the wall), and of course the finish coat plaster will break as it will have no strength against such movement.

Generally, when joining plasterboard I suggest that where the two pieces are fixed to the same support along the edge, you butt-join them. Where they are not fixed to the same support along the joining edge, leave a 1/4" gap and force bonding coat right through to form a snot or nib (depending which part of the country you live in) oozing out the back and the gap filled. This will bond the plasterboard edges together rather well. Then in either case, tape scrim across the join and plaster over with a finish coat.

[Rich]

Ok thanks guys.

[Rich]

I have been thinking (dangerous i know!) about paper tape. Where is paper tape to be used if not to join two boards?

The problem i have is that there are a few gaps of about 10mm between the boards; and the backgrounds vary from stud walling to dot & dabbed to brick.

I am not sure if pushing bonding coat in will do much, except run down the back of the board?

I will try a test patch on this as i can always cover it!

Regards,

Rich

[Andrew Gabriel]

I've never used it, but I think it's used when you aren't plastering the plasterboard. There was also a technique where you use bevel-edged board and only plaster in the bevelled joins, and I think it might be used there, but again, I've never done that. This required the two boards to be screwed to the same support member along the join so there's no relative movement, and it doesn't sound like yours are.

Well, if that's all it's for, you can make it up a bit thicker, or wait until it's started going off a bit before forcing it in the larger gaps.

[Rich]

Thanks Andrew.

I will be attempting this at the weekend...

Regards,

Rich

[Cycle]

Andrew Gabriel,

do you know whether your bonding plaster/nib technique would be useful for repairing persistent cracks in an existing ceiling (cracks that run along the edges of the underlying plaster boards and at rightangles to the joists)?

The plaster boards were originally close butted together. I was wondering about opening up the width of the crack to around three millimetres by using a Rotozip type of tool - the bit diameter is three millimetres. Would forcing bonding plaster through this gap, followed by scrim and reskimmimg of the ceiling be likely to make a good repair?