dot and dab or not

[colw1]

hi I have had an extension shell built and have got to plasterboard the internal walls but am wondering about the process of dot and dab.
firstly how close to the block can the new plasterboard be pushed and how many dot do you need
Also I would like to know if the plasterboard can be fixed to the blockwork directly with let say screws and plugs or is there any other methods or links to explain
thanks col

 

[noseall]

i put trowel size (small plastering trowel) dabs on the boards - 4 blobs across a 1200mm board and space them the same down the 2400mm run.

the dabs do not want to be too small for two reasons;

1. the wall may not be perfect and larger dabs will afford you a greater working tolerance. (the board can still be tapped back fairly snug, squashing the dabs)

2. a smaller thinner dab can dry out too quickly particularly on a porous wall. this may lead to an adhesion failure.

you usually end up with a finished thickness of around 25mm when using 12.5mm plasterboards, dabs and skim.

 

[vbpupil]

I have recently used the D&D method in my new extension (5m x 4m), had never done it before and seen it done on telly. Its real easy to do and i had no real problems.

The only thing i found was that in areas where 2 boards meet just be aware of putting the same amount on each board - sounds obvious but when your struggling with a full sheet on your tod it can be a real pain in the butt, the adhesive will squash down to a point. Also be sure to use a level to make sure the boards are level.

Also i found it better to make the mix a little wetter, having never done it before my first batch was on the dry side and it made it real difficult to work with. you'd be better off buying a plasterers whisk cause you tend to go through quite a bit of the D&D mix in a very short space of time.

I wouldn't bother with plugs and screws sounds like a real long job to me.

Hope it helps.

 

[Plastile]

Hi Col,
300mm centres is good for the dabs, as noseall said, beware of an uneven wall just check for high points, mark where you are putting the dabs on the wall first, you can then put one dab in the centre of 2 boards, thus eliminating any problems of uneven dabs, they will push in, idealy you want the boards as close as can be, i usually go for 3-5mm, so to give good fixings into the wall for furniture etc.

 

[Peadee]

Dot and Dab is the way that most plasterers do it nowadays. I would just say this, always dab the wall and not the board and don't ever apply any PVA to the wall. Board glue is made to be applied to porous walls. If walls are extremely dry and dusty you can damp them slightly with water but never PVA them. I do this with a hose pipe with a fine mist, dont soak the wall just damp it. If you are working alone use 4x3 boards, they are much easier to handle and get yourself plenty of little blocks of wood ready to rest the boards on to stop them slipping down. I have a bag full of 2 inch blocks for this.
I have found that "LaFarge" board glue is the best. Get a large gorilla tub fill it with water to a level 8 inches from the top, chuck in one bag of glue and mix. Wait 5 minutes and mix again and it's ready to go. The instructions are on the bag anyway so if you have a different size tub you can add the required amount of water and then measure from the top of the tub and then you will know how much water you need for each mix.
You will also need a couple of lengths of 4x2 timber for tapping the boards into place, I have a 1foot and a 2 foot length. Use the narrow edge to tap with.
Don't dab the boards, they gat so heavy that they are a bitch to handle.
Good luck.
PS..... 1 bag of glue should be enough for 3 8X4's or 8 4x3's on good, even walls.