# Painting a ceiling: preparation, water stains, plasterboard and ladder safety > How to prepare the ceiling, seal an old stain only after the leak is fixed, treat plasterboard joints and work safely on a ladder, based on technical data sheets. - Page: https://paredecerta.pt/en/guides/painting-ceilings-technique-stains - Language: English - Updated: 2026-11-03 ## Summary - A water stain is sealed only after the leak is repaired and the ceiling is dry. The data sheets always speak of dry stains. - The CIN stain blocker we read takes 1 to 2 coats and covers 9 to 11 m²/L per coat. Below 10 °C or above 80 % humidity it blocks less well. - On plasterboard, joints and nails are filled, sanded and primed. Repairs need a fresh coat of primer. - Use the ladder only for short jobs, with three points of contact and never on the top three rungs. The ceiling is where paint shows its flaws most: raking light catches every imperfection, and a water stain can come back months later. This guide covers what to prepare, which paint and primer the technical data sheets call for, how to deal with an old stain, and how to work safely on a ladder. *Updated on 3 November 2026. General information, not a substitute for an assessment by a professional.* ## The essentials - A water stain on a ceiling is sealed only **after the leak is fixed** and the ceiling is dry. The data sheets always speak of **dry stains**. - The stain-blocking primer we read (CIN) takes **1 to 2 coats**, covers 9 to 11 m²/L per coat, and the topcoat goes on afterwards. On new surfaces, 2 coats. - On **plasterboard**, joints and nail heads are filled, sanded with care and **primed**. Without this, joints and repairs show as patches of different sheen or colour. - The matt ceiling paints we read call for 2 to 3 coats and cover 8 to 14 m²/L. - The ladder is for short jobs only. Never stand on the **top three rungs**. ## First, what lies under the paint Most ceilings in recent homes are **plasterboard** or **sprayed stucco**. The data sheet for CIN's EP/GC 300 primer (revision January 2024) says that on plasterboard you should **level the joints and fill the nail heads with filler** (Hantek) and **sand carefully** so the surface is flat. Hantek filler goes on with a spatula in thin layers of 1 to 2 mm, hardens in about 24 hours and is sanded before painting. Then comes the primer, one coat, to **seal and even out absorption**. The sheet warns that if the primer is sanded off, or there are repairs, those areas need **a new coat**. Otherwise the topcoat is absorbed unevenly and some areas differ in tone or sheen. The Hantek sheet says the same: sealing repaired areas with primer avoids staining caused by differences in absorption. On **sprayed stucco**, the same sheet asks for a finishing layer of even thickness, 1 to 2 mm. **Loose old paint.** If the ceiling was painted before, CIN says to **brush off paint that is not bonded** and repair damaged areas before painting. See [peeling paint and stains](https://paredecerta.pt/en/guides/peeling-paint-stains). ## Which ceiling paint The sheets we read give no standard for a separate "ceiling paint". Matt interior paints for walls and ceilings are the same products. | Paint | What it is for, per the sheet | Coverage per coat | Coats | |---|---|---|---| | CIN Wet on Wet (rev. August 2026) | Interior walls and ceilings, dead matt | 10 to 13 m²/L | 2 | | Barbot Branco Total (28/02/2025) | Interior walls and ceilings, plasterboard and sprayed stucco | 8 to 10 m²/L | 2 to 3 | | Barbot Extrapaint (19/09/2023) | Interior walls and ceilings, plasterboard and sprayed stucco | 10 to 14 m²/L | not checked | A **dead matt** finish (gloss of 5 or less at 85°, per the sheets) reflects less light, and CIN says of its Vinylmatt that it helps hide small imperfections. That is not unique to ceilings, but it explains why matt is so common there. To choose a paint room by room, see [which paint for each room](https://paredecerta.pt/en/guides/which-paint-for-each-room). For litres, the [calculator](https://paredecerta.pt/en#calc) adds the ceiling to the wall area. The Wet on Wet sheet allows **wet-on-wet** application: the second coat may follow the first before it dries, or after 6 hours. It is touch dry in about 30 minutes at 20 °C and 60 % humidity. The sheets list a **drip-free roller**, brush or airless gun, and air above 5 to 8 °C with relative humidity below 80 %. ## Water or smoke stain on the ceiling 1. **Find and fix the source.** Pipe, roof, bathroom upstairs. See [leak from upstairs: who pays](https://paredecerta.pt/en/guides/leak-from-upstairs-who-pays) if the water comes from another flat. 2. **Let the ceiling dry.** The Barbot Branco Total sheet lists, among its conditions, **substrate moisture below 5 %**. We do not know how that is measured at home. A ceiling still cold and damp to the touch is not ready. 3. **Brush off** anything loose. If there is mould, treat it first with an anti-fungal product (CIN says not to use bleach) and see [mould on walls](https://paredecerta.pt/en/guides/mould-on-walls). 4. **Seal the stain** with a stain-blocking primer. CIN lists Stop Manchas (sheet of July 2013) for concrete, cement, plaster and stucco: 1 to 2 coats, touch dry in about 4 hours, recoat after about 6 hours, at 20 °C and 60 % humidity. Aqua Primer (February 2020) is touch dry in 1 hour. Both ask for air above **10 °C** and humidity below **80 %**. Below that, the ability to block stains drops. 5. **Paint** the whole ceiling, wall to wall. Painting only the patch often leaves a mark of a different colour. This is common practice, not mentioned in the sheets. 6. **Wait a week or two** and watch. If the outline reappears, water is still getting in. Do not repaint before you find it. ## Cracks and joints The Barbot Branco Total sheet separates cracks up to 2 mm (open with the spatula edge and fill), cracks over 2 mm (open, clean, and consolidate with primer if the surface is powdery) and **dynamic cracks**, treated with elastic filler reinforced with glass fibre, in layers up to 3 mm. If a crack moves or grows, it may be structural: filler and paint alone are not the answer. ## Technique and safety Rolling a ceiling tires the arms and flicks drops into your face. The CIN sheets ask for **eye protection, gloves and suitable clothing**. The rest of the technique (a strip along the walls with a brush, overlapping roller passes, an extension pole) is common practice. We did not find it described in the sheets. On ladders, the Azores regional government document (Occupational Health and Safety Office) asks for a **solid, level and stable** base, an angle of **60 to 75°** (a 4 m ladder should stand 1 m from the wall), **three points of contact**, tools in a bag, both feet on the same rung, never on the **top three rungs**, and hand ladders only for **occasional, short jobs**, with a ladder no longer than **3 m**. Prepare the surroundings too: [preparing the home for painting](https://paredecerta.pt/en/guides/prepare-home-for-painting-furniture). ## What we could not confirm - **How long before a stain returns** after sealing: the sheets give no data. - **Acceptable ceiling moisture**: Barbot gives "below 5 %" for the substrate, but not how to measure it at home, nor whether it applies to plasterboard. - **Other makers' sheets** for stain blockers: we read CIN. Barbot names Barbolite Premium for smoke or nicotine stains, and we did not read its own sheet. - **Roller and brush technique**: common practice, no source. - **Prices** for painting ceilings: see the [cost guide](https://paredecerta.pt/en/guides/interior-painting-cost). ## Sources (read on 3 November 2026) - CIN, [Primário EP/GC 300 10-600](https://idoctec.cin.com/Home/Document/10600-DEC-CIN-BT-PT), January 2024; [Hantek 15-950](https://idoctec.cin.com/Home/Document/15950-DEC-CIN-BT-PT), January 2019 (joints, primer, absorption). - CIN, [Primário Stop Manchas 45-335](https://idoctec.cin.com/Home/Document/45335-DEC-SOT-BT-PT), July 2013; [Aqua Primer 12-830](https://idoctec.cin.com/Home/Document/12830-DEC-CIN-BT-PT), February 2020 (stain blocking, times, conditions). - CIN, [Wet on Wet 21-450](https://idoctec.cin.com/Home/Document/21450-DEC-SOT-BT-PT), August 2026; [Vinylmatt 10-250](https://idoctec.cin.com/Home/Document/10250-DEC-CIN-BT-PT), July 2026; [Artibiose 18-230](https://idoctec.cin.com/Home/Document/18230-DEC-CIN-BT-PT), August 2026. - Barbot, [data sheet 1743 Branco Total](https://barbot.pt/wp-content/uploads/2025/12/1743-barbot-ft-branco-total-pt-rev.1.pdf), 28/02/2025 (paint systems, cracks, conditions); [1272 Extrapaint](https://barbot.pt/wp-content/uploads/2025/09/1272-barbot-ft-extrapaint-pt-rev.04.pdf), 19/09/2023. - Governo dos Açores, Gabinete de Segurança e Saúde no Trabalho, [Trabalhos em altura: utilização de andaimes e de escadas](https://gestirt.azores.gov.pt/files/documents/2022/03/34885692f35091ba05030bb4d876b686da17bff7.pdf), undated. ## FAQ ### Can I paint over a water stain? Only after the leak is repaired and the ceiling is dry, and with a stain-blocking primer. Ordinary paint lets the stain bleed through. ### How many coats of stain blocker? The Stop Manchas sheet (CIN, July 2013) says 1 to 2 coats, 2 on new surfaces, recoat after about 6 hours. ### What about plasterboard joints? CIN (EP/GC 300, January 2024) says to level joints and fill nail heads with filler, sand with care and apply primer. ### The stain came back. Why? Water is probably still getting in. Find the source before repainting. --- Source: https://paredecerta.pt/en/guides/painting-ceilings-technique-stains. Independent information, not legal or tax advice.