Quality Standard Q1-Q4

This quality system is a European standard developed in accordance with the Estonian standards of finishing construction works. The Q1—Q4 system is a set of recommendations for the preparation and assessment of surface quality depending on different types of finishing coatings. Numbers 1, 2, 3, 4 are the designation from lowest to highest, where Q1 is the lowest quality value and Q4 is the highest.

Q1 — there are no requirements. The vertical deviation tolerance is 3 mm by 2 linear meters; there are obvious recesses, scratches, visible scuff marks and tool prints (possible depth up to 3 mm); local surges of plaster (putty) mortar (no more than 2 mm high; shadows in side light. Such a surface is suitable for the following finishing coatings: for laying on top of ceramic tiles, for finishing with decorative plaster with a grain of more than 2 mm, for wall cladding with decorative elements on glue.

Q2 — the requirements are normal. Vertical deviations of 2 mm by 2 linear meters are allowed; there are visible notches, scratches, scuff marks and tool prints (up to 1 mm deep); local surges of plaster (putty) mortar (no more than 1 mm high; shadows in side light. This treatment is suitable for fiberglass, structural and liquid wallpaper, thick vinyl wallpaper, texture paint and decorative plaster with a grain of 1 mm.

Q3 — the requirements are high. Vertical deviations of 1 mm by 2 linear meters are allowed; there are visible scratches from the grinding abrasive (up to 0.5 mm deep); shadows in side light are less than in Q2. The following are not allowed: visible recesses, scuff marks and tool prints; local surges of plaster (putty) mortar. It is suitable for coating with matte paint, for gluing thin wallpaper and decorative plaster with a grain of at least 1 mm.

Q4 — maximum requirements. Vertical deviations of 0.5 mm per 2 linear meters are allowed. The same as in Q3 is not allowed, as well as visible scratches from the grinding abrasive and shadows from the side light. This level of surface treatment is suitable for further wall coating with semi-gloss paint, Venetian plaster, for lacquer or mother-of-pearl coatings and for metal wallpaper.