Dot and Dab

[Dragonrider]

Quick question, seeing I'm starting this on Monday......

Dot and dabbing plasterboard to a (hopefully) brick wall, could be stone for all I know.

Is it regular plaster, or do I need an additive please?

I can plaster, I can build a stud wall, board and skim, and I've seen dot and dab done, but until Monday, or Tuesday, depending on how much of the plaster wants to stay on the wall, I've never done it myself....

Oh are we looking forward to this......

 

[MANDATE]

For dot & dab I think you use a 'plasterboard adhesive' specially for the purpose.

 

[DAZB]

You want Dry Wall Adhesive for Dot & Dab . Brush your wall down with a coat of Sealobond ( PVA ) beforehand and you will be ok.

 

[AdamW]

It's called Dot and Dab, but a more apt name would be Splodge and Dab.

The "dots" are actually quite big. I would say a splodge should be about the size of a digestive biscuit, and about a half an inch at the thickest point. Press the plasterboard against it, and slide it around to spread out the adhesive and push out air bubbles.

Anyone want to quote an ideal interval for the dots?

What I then did was to drive 3" screws through the plasterboard into the masonry at regular intervals, these held pretty tight despite there being no plugs. The screws hold the board in place until the adhesive dries.

 

[MANDATE]

From what I've seen the finished plasterboard stands away from the wall by 10 mm so the thickness of the dab needs to be at least 3 times this amount. This will offer some resistance and helps in aligning the board, having previously marked floor and ceiling you use straight edge to run floor to ceiling in conjunction with hammer to give a flat and vertical surface.You also have to take into account the dabs when flattened will give increased area and good adhesion and there is no need for any other support.

 

[AdamW]

The screws aren't there to act as primary fixing for the board, they hold it there until the adhesive dries. Still, they can't hurt even then.

You wouldn't put up some coving without a few nails to hold it in place would you? Or glue on some skirting board without something holding it in place before the glue dries?



How far apart would you recommend the dabs? I believe there should be about 300-400mm between them, would you agree with this?

 

[MANDATE]

Adam!
Surprise! surprise! I agree about the spacing. Now it just so happens I recently fitted coving and new skirting boards, both secured with adhesive only. No Nails! well thats not quite true, I did use 'No nails' on the skirting boards.

 

[AdamW]

What, plaster coving?! You can do polystyrene coving with adhesive only, because the polystyrene is very light. But I am pretty certain the plaster coving must be supported until the adhesive is dry, and this is usually accomplished through banging a few nails in underneath the coving and in front of the coving (not actually through it!).

If you have dotted and dabbed without supporting the board and it was fine, then I am proven wrong. When I did it I used big blobs of gripfill (a bit more expensive than plasterboard adhesive!), and the screws held it in place, and are still there just to be on the safe side.

 

[DAZB]

If you mix your adhesive to the correct consistency and not too runny then you will find that you do not need to fix nails or screws as well. Have a go at pulling a full board off the wall when it has about a dozen good sized blobs of adhesive and has been tamped flat and level. It's not easy because of the suction of the stuff. As a rule I mix the adhesive until you can turn a trowel full upside down and it doesn't fall off and I have never had a board come off yet.

 

[Stod]

I've put up the full size (5 in) plaster coving with adhesive only. There's so much suction that you do not need anything else other than the correct adhesive. Only problem is that it smells like chicken s***.

 

[AdamW]

In that case it would seem I stand corrected

But I really wouldn't recommend it, it is a gamble. Sometimes adhesive seems to grab, then you come back 5 minutes later and it has gone. Even worse, if it takes a long time to set and you come back the next day and find whatever you have stuck is now, erm, not stuck. Or even worse, just a few degrees off where you left it and stuck fast (and now the mitred corners on the coving don't match!)

You should always properly secure anything relatively heavy that you adhere to any other surface. Its just not worth the risk.

 

[Dragonrider]

Thanks Guys,

Appreciate the replies and suggestions.

I'm going with bonding plaster, the wall will get a sluice of pva bond first (YUK - Messy!) and will try to get the mix right and slap it on, board up against it, then bang, bang, bang with a good solid piece of wood to secure the board to the mix, and screw or nail to hold it whilst the dabs go off.

 

[masona]

Agreed with AdamW, it best to run a couple of nail for the coving to rest.
1, To stop it sliding down.
2, The nail position will give you the correct angle, equal width top & side therefore the internal or external corner will be fitted correctly. I can't see how you can put a long length of coving and not knowing the coving is set at 45 degree angle.