Skim coating in Batumi: walls for paint and wallpaper

What a skim coat fixes and what it doesn't

We skim walls after plastering or over plasterboard, and a skim coat has one job: smoothness. A layer of one to three millimetres covers pores, pits, straightedge marks and small ripples, but it won't fix a wall that leans over its height or an out-of-square corner. If the gap under a two-metre straightedge is more than a few millimetres, we first decide how to level the walls, and only then skim them.

Tiles don't need a skim coat. Adhesive goes straight onto the plaster, and an extra soft layer between them only weakens the bond. We skim walls for paint, wallpaper and thin decorative coatings, and plasterboard ceilings also to cover the joints and screw heads.

Layers: base coat, reinforcement, finish

Before the first layer, we measure the moisture in the plaster and prime the wall. Then the order is as follows:

1. A coarse-grained base coat fills pits, guide bead grooves and joints, and on plasterboard the joints between the boards, together with tape.
2. Over the joints between blockwork and concrete columns we apply mesh, lapping onto both sides. If the wall has fine cracks, we embed glass fibre lining over the whole area into the fresh base coat.
3. The finishing coat goes on in one or two thin layers, depending on the level in the estimate.
4. We sand with fine abrasive, remove the dust and prime again, this time for paint or wallpaper.

Each layer dries before the next one goes on. A finish applied over a damp base coat gives shrinkage cracks, and they show only after painting. We sand with a sander connected to a vacuum, especially once the windows and doors are in: skim coat dust gets into every gap.

Q levels: which skim coat your finish needs

Smoothness is described by levels from Q1 to Q4. Gypsum system manufacturers use them, and we write the level for each room into the estimate: that way it is clear before work begins how many passes you are paying for.

We choose the level by the light and the paint, not by the name of the room. Deep matt white paint forgives more than semi-matt grey, and a wall facing a window gives away unevenness less than a wall along which the light falls from the side. If you are still choosing how to finish the walls, see the comparison of paint and wallpaper: the level and the estimate depend on that choice.

Joints, cracks and reveals

Cracks in a fresh skim coat almost always appear in the same places, and you can tell where to expect them before the work starts. The vertical joint between blockwork and a concrete column cracks because concrete and block respond differently to heat and moisture. We cover it with mesh in the base coat, lapping well onto both sides, and if a crack does appear, it won't come through to the finish.

The corner between wall and ceiling can't be cured with mesh. In a cast-in-place concrete building, the slab deflects slightly in the first few years, and a rigid layer in this corner tears whether it is reinforced or not. So we don't take the skim coat rigidly into the corner: we leave a thin separating cut and fill it with flexible paintable sealant, or the corner is covered by a moulding. Where this crack comes from and how it is dealt with in a finished renovation is covered in the overview of wall and ceiling finishes.

The same goes for windows. A uPVC or aluminium frame moves with sun and cold, and skim coat taken onto it comes away in a strip along the profile. We bring the reveal up to the frame with a gap and close the joint with the same sealant. For wall painting and wallpaper hanging we hand over these places like the rest of the wall: sanded and primed.

How much skim coating costs in Batumi

Skim coating walls for painting costs from 23 ₾ per m², with the usual range up to 36 ₾. That is the labour; materials are extra: primer, filler and paint for a wall to be painted come to 16–24 ₾ per m². Wall priming as a separate job costs 4–7 ₾ per m², and two coats of paint after skim coating 23–36 ₾.

A plasterboard ceiling is priced as one line: filling and painting cost 42–54 ₾ per m². Level Q4, reinforcing cracked walls, removing old paint and whitewash, and lots of reveals and corners push the price towards the upper end. Flat fresh plaster for level Q2 or Q3 is closer to the lower end. The final cost is set after the site measurement and once the estimate is agreed.

How we sign off a skim coat

The main sign-off tool here is a lamp. It is placed on the floor or moved along the wall so that the light falls almost parallel to the surface, and this raking light shows ripples, trowel marks and sanding scratches that can't be seen in ordinary light. We look at each wall from both sides, and at the wall by the window in daylight as well, in the light it will be seen in.

We mark what we find in pencil, touch it up and sand it before the certificate. If you are signing off the stage by video, the foreman films the wall with the lamp in hand. We look separately at places where mistakes from neighbouring work show through: plasterboard joints, junctions with columns, guide bead grooves, the edges of back boxes. Walls with mould go through a separate job before skim coating, mould removal: a skim coat over a patch doesn't stop it.