Traditionally, the quality of a surface has been judged subjectively, with the use of phrases such as “ready-for-painting”, “ready-for-covering” and so on. However, these are not suitable for describing the level of finish. A “finished” and “ready-for-painting” surface for one person may be a sub-standard one for another.
The quality of finish of gypsum board is defined by the Euro Gypsum standards (based on EN 13963). The level of finish is affected by the dimensional tolerances of boards, metal framings and level of workmanship. The flatness of the drywall and ceiling also impact the level of finish.
Local Flatness Standards
A ruler of 200 mm applied on the cladding of the drywall, particularly at the joints, must not have a difference bigger than 1 mm between the most salient point and the point furthest away.
General Flatness Standards
A ruler of 2000 mm length applied to the face of the drywall and moved in all directions must not have a difference bigger than 4 mm between the most salient point and the point furthest away
Jointing and finishing stages
The jointing of gypsum board goes through stages Q1 and Q2 and finishing from Q3 to Q4.
|Filling the joints between the boards with Pro-Fill / Easi-Fill and tape
||Q1 + levelling the joint to the board surface with Pro-Fill / Easi-Fill
||Q2 + a tight coat (1mm) over the entire board surface with Pro-Fill / Easi-Fill
||Q2 + a skimming coat of Gyproc Champion Skimming Putty (>1mm) over the entire board surface
Shallow light (natural or artificial) can affect the appearance of the surface. Ideally, lighting conditions where the board systems are used should be known in advance. The surface quality should not be judged by flood-lighting, and the limits of manual workmanship should be considered.
Specifying the expected finish quality
If no quality level is specified, then quality level Q2 is assumed by default.
Performance Benefits of Q4 levels of Finish
A Q4 finish delivers far superior aesthetics. This level of finish also offers significant performance benefits in acoustics and fire safety.
Effect on Acoustical Performance
Cracks affect acoustics or isolation of a drywall by "flanking" the sound. Sound can flank over, under, or around a wall or through air gaps. Noise passes through spaces at the weakest points. This air-gap, or "flanking" path, can seriously degrade the isolation quality of a wall.
- A tiny crack/gap of a width of 0.1mm can reduce the overall insulation performance of a drywall by 15%
- A crack/gap of a width of up to 0.5mm can reduce the performance by approximately 35%
- A crack/gap of 1mm will give a dismal performance of 50%
Effect on Fire Performance
A fire-resistant system acts as a shield against fire, heat, smoke and harmful gases. Cracks or gaps reduce the fire-resistance of a drywall. Smoke and gases can easily pass through such cracks or gaps and cause discomfort and health hazards.
A Q4 level of finish not only improves the look and feel of the interiors, it also delivers superb acoustic and fire safety performance.