Day 25: Plasterboard Dot and Dab on Walls
Today rain prevented the roof team from finishing above so all hands were working inside. The rest of the roof rafters were insulated and plaster board put up. Plaster board was screwed to the roof rafters and stuck to the brickwork with the dot and dab method.
What is dot and dab?
Dot and dab is simply a way to stick plasterboard to a block wall. Plasterboard is screwed to ceiling rafters and stud walls but it cannot be fitted to blockwork or bricks in this manner.
It should not be used in outbuildings because it is not a way to stop moisture because the adhesive will form a bridge between the wall and the plasterboard, but it does help air to circulated behind the board.
Before dot and dab walls would have to be given two layers of plaster before they could be painted. Dot and dab allows you to put up the boards and paint on the same day. They are a quicker way to build a room. For our extension we had the plasterboards covered in a layer of plaster to give a better finish. This seems to be easier than trying to make the boards fit perfectly.
How to dot and dab
To do this you simply apply dot and dab (also known as Dry Wall / Dri-Wall Adhesive) Dot and dab is an adhesive that is made from gypsum.
Once mixed the adhesive is applied in spots over the wall at regular intervals, or sometimes in strips around the boundary where the plasterboard will go. The plasterboard is then pushed onto the wall where it will stick.
An expert on the DIYNot.com website desribed his method:
“If you put small dabs on close together when you “tap” it against the wall with your 4″x2″ to plumb it up the dabs will spread and there are hardly any voids behind the board and it is a lot firmer against the wall!!! Mind you I’ve only been dot and dabbing for 20 years!!!” Roy C. Read more: http://www.diynot.com/forums/viewtopic.php?t=140415#ixzz31RK4zQA9
So the idea is that there is an almost, or completely, continuous cover of the adhesive once the plasterboard is pushed on and tapped to make sure it is flush and level.
Plasterboard needs to be placed on the wall within 30 minutes of application otherwise it will dry out and no longer stick.
How much dry adhesive do you need?
The British Gypsum website says: “One bag (25 kg) will adhere approx. two 1200 x 2400mm (8 x 4’) plasterboards.”
Some architect guidelines suggest 2.5 bags are needed for every three boards. They like a complete covering, and this suggests that a complete covering is more secure. Although many builders will put on less with no problems.
Advantages of dot a dab
Another advantage of dot and dab is that when it is covering all the area behind the wall, it provides a solid anchor for a rawl plug. You can drill through the plasterboard board and through the adhesive and insert a small masonry plug.
It is much more solid than plugs in stud walls, and you do not need to worry about drilling into the brickwork. Of course, if you are hanging something heavy you still need to drill into the blocks.
Tommy’s Trade Secrets – How To Dot And Dab A Wall
See an expert in action. A step by step guide to plastering.
Photos of the plasterboard on the walls