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Interior and exterior emulsion paint is the first finish people see in a factory's offices, canteen and control building. World Steel starts skimming only when the plaster has been accepted and is dry enough, and when roofs, toilets and balconies have passed their waterproofing acceptance. The work then follows a fixed sequence: skim coat, sanding, primer and two finish coats.
Preparation
- Tools: handheld moisture meter, fine sandpaper, paddle mixer, skimming knife, rollers, brushes, inspection lamp, drop sheets.
- New masonry must have enough time to dry and cure (21–28 days). Rub the wall down with a rubbing stone to remove contaminants and even it out; follow with coarse paper and remove dust with compressed air or a damp cloth.
- Existing walls: wash off moss, mould, flaking paint and grease; scrape off paint and skim that have lost adhesion, rinse with clean water and let dry.
- Check wall moisture before skimming: 25–30% on a handheld meter is acceptable. If the wall is too dry, roll on a thin coat of water before skimming.
Interior painting
| Step | Work | Control |
|---|---|---|
| 1. Mixing the skim | Machine mix to the manufacturer's ratio (commonly 1 part water to 3 parts powder by weight) until smooth and lump-free. | Do not use skim mixed longer ago than the permitted time. |
| 2. First skim | Apply with a skimming knife; remove dust before the next coat. | Hold an aluminium straightedge to arrises so they are straight and sharp. |
| 3. Second skim | Apply the second coat; after 24 hours sand flat with fine paper. | No coarse paper that scratches the skim. Keep the total skim thin (usually no more than 1 mm per coat). |
| 4. Lamp check | Shine a lamp across the wall to check flatness; touch up high and low spots no more than twice; remove dust; leave to dry for 24 hours. | Accept the skim before painting. |
| 5. Primer | One coat by roller or spray, standard wet film about 100 microns; thin with a suitable solvent up to 10% by volume. | Lay drop sheets so material does not fall on other elements. |
| 6. Finish coats | At least two finish coats; thin with up to 10% clean water by volume; 2–3 hours between coats. | Check the surface with a lamp; clean tools with a suitable solvent. |
Exterior painting
- Inspect and install the suspended platforms before work starts; check wall moisture (25–30%).
- First skim with exterior-grade skim; when it is dry (usually after 1–2 hours) apply the second; after 24 hours sand flat with fine paper.
- Sand and dress recessed grooves, arrises, drip edges and drip grooves under window sills so they are straight and sharp.
- Apply one primer coat and two finish coats about 2 hours apart, by spray or roller.
- Paint the exterior before the interior where possible, to avoid moisture through the external walls; paint high areas first.
- Paint a wall panel in one continuous session, never in two separate sessions; cut in corners with a brush or small roller first, then use the large roller.
- Keep touch-ups to a minimum: after the first finish coat, wait until doors, electrical and floor work are done, then touch up and apply the second finish coat.
Acceptance criteria
- Skim flat, smooth, fine and clean; no pinholes or hollow areas; firmly bonded to the wall.
- Grooves, arrises and corners straight, sharp and square; a continuous cut-in line at the ceiling.
- Even paint colour with no light and dark patches, brush marks or roller marks; floors clean of skim and paint drips.
Common mistakes
| Mistake | Remedy |
|---|---|
| Skim dropped on floor tiles | Lay drop sheets at the wall base before work starts |
| Uneven colour from interrupted rolling | Roll a whole wall continuously |
| Paint on switches, sockets and door frames | Mask with paper tape; use small rollers and brushes in tight corners |
| Arrises not sharp, ceiling line not square | Sand corners and edges carefully; cut in the ceiling line with a small roller or brush |
| Paint film blistering or peeling | Measure wall moisture before skimming; never skim wet plaster |
| Materials leaned against painted walls | Pad with soft cloth, paper or foam |
| Uneven line where wall and ceiling colours differ | Cut the wall colour in at the ceiling line and finish it in the ceiling colour |
Safety and environment
- Paint and skim free of lead and mercury; tins kept closed and stored safely.
- Dust masks when sanding, safety glasses when painting; good ventilation during work and drying, or breathing apparatus where ventilation is poor.
- No paint poured into drains or watercourses; waste paint disposed of under environmental rules; store in a dry, cool, ventilated place.
Reference standards
The edition in force when the contract is signed applies.
- TCVN 8652:2012 Emulsion wall paints – Specifications
- TCVN 5674:1992 Finishing works in construction – Execution and acceptance
