Indy Total Construction

To plaster a newly built wall you will not have to do any preparation work to it at all before you fix wooden grounds or metal lath in place.

Then the masonry should be dampened by splashing on clean water with a paintbrush. This will help slow down the rate at which the wall absorbs moisture from the plaster, preventing it from drying out too quickly and possibly cracking.

It is a good idea to practice scooping plaster from the hawk and applying it to the wall before you attempt the job for real. Set the loaded trowel against the wall so that the bottom corner of the blade rests on the ground or bead and the blade is at an angle of about 30° to the wall surface. Move the blade upwards to spread a vertical strip of plaster next to the thickness guide, keeping the blade resting on the guide and gradually reducing its angle as the plaster spreads.

Apply more strips of plaster in the same way, working upwards from the bottom and across the bay adding a good thickness of plaster to the wall.

When the bay is finished, use the long wooden rule to strike it off level with the thickness guides. Place it across the guides and draw it upwards, moving it from side to side in a sawing motion as you go. This will level off the high spots and accentuate the dips. Add more plaster and repeat the process until level.

Before it sets, key the surface for the finishing coat by passing a wooden float, with nails knocked through its face, over the plaster to leave score lines.

When the floating coat has hardened (it should take about two hours), you can apply the finishing coat. This is done in exactly the same way as plastering wallboard, applying two thin coats of Finish plaster to produce a polished, flat and hard surface.

Directions:

1. Scooping plaster from the hawk; put the trowel into the plaster and scoop forwards and upwards.

2. Practising applying paster to the wall; work upwards from waist-height, starting with the trowel at 30 degrees to the wall.

3. As you apply the plaster, tilt the trowel more parallel to the wall surface; keep the hawk close to the wall to catch droppings.

4. Applying the plaster in vertical strips; at the end of each stroke, press the lower edge of the trowel to firm the plaster onto the wall.

5. Ruling off the completed bay; use a straight-edge with a sawing motion to lower any high spots and to show up areas with too little plaster.

6. Scoring the surface to provide a key for the finishing coat; the nails should protrude in through the float.

7. Filling the gap left after taking off the ground batten; level off with the trowel, flush with the hardened plaster on each side.

8. Applying the finishing coat; work from bottom to top and cover the floating coat with a thin layer; apply a second coat. 9 Polishing the finishing coat; wet the surface sufficiently to remove ridges and marks and polish firmly with a perfectly clean, flat trowel.

You need only apply two very thin finishing coats directly over the drywall.

The plaster needed for the job is sold ready mixed or in a powder form requiring only the addition of water. It is mixed in the same way as other plasters and has a creamy texture.

Because you are only applying a finishing coat to the drywall board there is no need for thickness guides, except at any external corners.

It is a good idea to practice scooping the plaster from the hawk on to the trowel first, using a spare piece of drywall to try your hand at spreading the plaster and making it stick to the board_ The technique is to hold the hawk in your left hand (or right if you are left handed) so the top is level and set the trowel blade on edge, so it is at right angles to the top of the hawk. Use the trowel to push some plaster towards the edge of the hawk, scooping it off at the same time as tilting the hawk towards you. The whole is done in one smooth movement.

The first job is to seal the joints between the individual panels of gypsum board, reinforcing them with perforated paper tape or nylon tape to prevent the plaster cracking. The standard paper tape is available in 2in wide rolls of 50-500 feet.

Cut strips of tape to run the length of each joint, including any horizontal ones, before you begin plastering. They must be exactly the right length and should not overlap or be folded, otherwise the plaster will not grip the wall properly.

To seal the joint, spread a thin layer of plaster, about 4in wide, along it from bottom to-top. Hold the trowel so that the blade is at an angle of about 30° to the wall, reducing it as you move up the joint and the plaster on the trowel thins.

While the plaster is still wet, press the tape into it. The easiest way to do this is by draping one end over the blade of the trowel and pressing this into the plaster at the ceiling. Then gently slide the trowel down the plaster, positioning the tape with your other hand. Once the tape is in place, run the trowel carefully up the plaster to make sure it is bedded properly. Treat all the other joints between the panels in the same way.

When the taped joints have dried — which should take about 11/2 hours — fill in the areas between them with more plaster. Work upwards from the floor, spreading the plaster in thin vertical strips and being careful not to build up ridges at the joint positions. Stop just short of the ceiling and work downwards from there to get a clean, sharp angle.

Unless you are working on a very small area, by the time you have finished putting on the first coat, the area you started on will be ready for the second coat. This should be about 1/sin thick and applied with long, sweeping strokes to eliminate ridges. Start at the bottom corner of the wall and work upwards and along to make one continuous coating.

Allow the plaster to set slightly and then go back over it with a clean trowel to smooth off the surface. Finally, when it has hardened fully, “polish” the surface by splashing clean water on to it with a paintbrush (about 4in wide) then sweep the trowel back and forth lightly. This will give a smooth, matt finish ready for decoration.