# Filling and skimming walls before painting

> Filler or finishing compound, how to apply it, how long to wait, sanding and when to prime, with times from manufacturers' technical data sheets.

- Page: https://paredecerta.pt/en/guides/skim-and-fill-walls-before-painting
- Language: English
- Updated: 2026-11-04

## Summary

- There are two jobs: filling holes and cracks with filler, and smoothing with a thin finishing compound.
- Apply on a dry, sound, clean surface. It does not hide mould or cure damp.
- Times depend on thickness: Aguaplast All 4 in says 24 h per mm, Barbot 2 h in 2 mm coats.
- Sand only when completely dry, wearing a mask, and remove the dust before priming.
- We could not read the CIN and Weber sheets.

Before painting, almost every wall needs some preparation: filling holes, smoothing scratches, levelling uneven patches. This is where the finish is won or lost, because paint shows every flaw. This guide explains the difference between filler and skim coat (the Portuguese "barramento"), how to apply them, how long to wait and when primer comes in. The drying times come from manufacturers' technical data sheets.

*Updated on 4 November 2026. General information, not a substitute for a technician's assessment. Always follow the data sheet of the product you buy.*

## The essentials

- There are two different jobs: **filling** holes and cracks (filler) and **smoothing** the surface, whole or in large areas (thin finishing compound).
- Filler only works on a **dry, sound, clean** surface. Loose paint, dust and grease come off first.
- Drying times depend on **thickness**. One sheet says 24 hours per millimetre; another says 2 hours in 2 mm coats. Read the one for your product.
- Sand only when the compound is **completely dry**, and remove the dust before painting.
- Filler does not cure damp. If the wall is wet or mouldy, deal with the cause first.

## Which compound for which job

Portuguese uses several words for similar work: massa, massa corrida, estuque, barramento. We found no official definition separating them, so we use the data sheets' terms: **filler** (enchimento) and **finishing compound** (acabamento).

| Job | Type | What the sheets say |
|---|---|---|
| Holes, cracks and large gaps, uneven walls | Powder filler | Barbot, Massa de Enchimento Interiores (ref. 8800, sheet of January 2013): fills holes, cracks and large gaps and levels uneven walls. |
| Smoothing a whole wall or renewing over old matt paint | Ready-mixed finishing paste | Aguaplast All 4 in (Beissier, February 2024): can go straight onto old paint, in coats up to 6 mm. |
| A very smooth surface for a quality finish | Extra-fine powder finish | Aguaplast Super Fine (Beissier, February 2024): extra-fine interior compound; application thickness 2 mm. |

The two Aguaplast sheets we read were hosted on the Robbialac website. This is not a brand recommendation: they are the sheets we could read in full.

## Prepare before applying

The three sheets agree on the basics. The surface must be dry, free of dust, grease or wax, and free of loose parts or poorly bonded paint. Barbot also says to seal or dampen very absorbent surfaces.

1. **Remove what is loose**, such as crumbling plaster and lifting paint. See [peeling paint and stains](https://paredecerta.pt/en/guides/peeling-paint-stains).
2. **Clean off dust and grease.** Kitchens and bathrooms need extra care.
3. **Treat each crack with the right product.** The Aguaplast sheet says dynamic cracks (ones that reopen) need dedicated repair products, not filler alone. To tell which crack is which, see [cracks and plaster before painting](https://paredecerta.pt/en/guides/cracks-and-plaster-before-painting).
4. **Know what the old paint is.** In older homes, sanding old paint raises dust. Read [old paint, lead and safe sanding](https://paredecerta.pt/en/guides/old-paint-lead-sanding-safety).
5. **Protect floors and furniture.** See [preparing the home for painting](https://paredecerta.pt/en/guides/prepare-home-for-painting-furniture).

### If the wall has mould

Do not cover mould with filler or paint. The Aguaplast sheet says to clean mould-affected areas thoroughly and treat them with an antifungal before applying. The Robbialac Hydroviplite primer sheet describes scraping, cleaning with water and bleach, rinsing again with water and applying a dedicated disinfectant. Do this with the room ventilated and with protection, and read [mould on walls](https://paredecerta.pt/en/guides/mould-on-walls) for the cause.

## Applying the compound

**Powder.** The sheets give the mix: 1 kg of powder to half a litre of water, for both Barbot and Aguaplast Super Fine. Barbot says to mix, preferably with an electric drill, until smooth and lump-free. Barbot's working time is 30 minutes, so do not mix more than you can use. Super Fine stays workable for about 24 hours at 20 °C.

**Paste.** All 4 in comes ready to use and goes on with a stainless steel spatula or trowel, or a roller.

**Common rules.** Apply between 5 °C and 35 °C (Aguaplast) or not below 5 °C (Barbot). Do not apply on surfaces exposed to constant damp. Indoors, the Aguaplast sheets ask for ventilation so the compound dries properly. Wash tools with water straight afterwards.

**Thickness.** The maximum on the Super Fine sheet is 2 mm; on All 4 in it is 6 mm.

## How long to wait

| Product (sheet) | Drying time on the sheet | Sanding and painting |
|---|---|---|
| Barbot Massa de Enchimento, ref. 8800 (January 2013) | 2 hours in 2 mm coats at 20 °C, "depending on thickness" | The sheet gives no sanding time. |
| Aguaplast Super Fine (February 2024) | 30 minutes per 0.2 mm; 24 hours per 2 mm | "After complete drying" |
| Aguaplast All 4 in (February 2024) | 24 hours per mm | "After complete drying" |

**Your product's sheet rules.** By those figures, 3 mm of a compound that dries at "24 h/mm" needs several days.

## Sanding and cleaning

Aguaplast says its compounds are easy to sand and warns against inhaling particles while sanding. Wear a mask and goggles, open the window and vacuum the dust. The Hydroviplite sheet recommends sanding beforehand when repainting and vacuuming the dust. Then wipe with a well wrung-out damp cloth. Dust on the wall ruins primer adhesion.

On ceilings, raking light shows every ripple: see [painting ceilings: technique and stains](https://paredecerta.pt/en/guides/painting-ceilings-technique-stains).

## Primer

It depends on the compound and the wall.

- The **Super Fine** sheet says it needs no primer before painting. But it says to treat absorbent surfaces with a stabilising primer if absorption needs reducing.
- **Hydroviplite** (Robbialac, sheet CC-VIP 132 16.1) is described as a sealer and first coat for any emulsion paint: one undiluted coat, touch-dry in about 1 to 2 hours and recoatable in about 4 to 6 hours, in normal conditions. Coverage is 10 to 15 m² per litre per coat.

To choose the paint, see [paint types](https://paredecerta.pt/en/guides/paint-types-emulsion-acrylic-enamel). For quantities, use the [calculator](https://paredecerta.pt/en#calc) and the guide [how much paint do I need](https://paredecerta.pt/en/guides/how-much-paint-do-i-need).

## How much compound to buy

Consumption on the sheets, per m² per mm: 1 kg (Super Fine), 1.75 kg (All 4 in), 0.7 kg of powder (Barbot). Our own sum with Super Fine: 20 m² at 1 mm comes to about 20 kg, one 20 kg sack.

## What we could not confirm

- **CIN and Weber sheets.** The CIN sheet we tried to open (ref. 18105) did not load and we did not read it. We found no Weber sheet for interior finishing compound. We cannot say what they state.
- **Sanding time for each compound.** The sheets ask for "complete drying" without giving hours.
- **An official definition of "estuque", "barramento" and "massa corrida".** We found none.
- **Prices.** We did not confirm compound or labour prices with a source.
- **Current version of the Barbot sheet.** The one we read is from 2013.

## Sources (read on 4 November 2026)

- Barbot, *Massa de Enchimento Interiores, ref. 8800*, technical data sheet, January 2013, [barbot.pt](https://barbot.pt/wp-content/uploads/2024/01/8800003-FT-M.-de-Enchimento-po.pdf) (use, yield, drying, preparation, mixing).
- Beissier, *Aguaplast Super Fine, technical data sheet, February 2024 v.1*, [sheet hosted on tintasrobbialac.pt](https://tintasrobbialac.pt/download/ficha_tecnica/ROB_004_0060/1/Superfine-ficha_tecnica.pdf) (read in full).
- Beissier, *Aguaplast All 4 in, technical data sheet, February 2024 v.1*, [sheet hosted on tintasrobbialac.pt](https://tintasrobbialac.pt/download/ficha_tecnica/ROB_004_0067/1/All-4-In-ficha_tecnica.pdf) (read in full).
- Tintas Robbialac, *Primário Hydroviplite, technical data sheet CC-VIP 132 16.1, undated*, [tintasrobbialac.pt](https://tintasrobbialac.pt/download/ficha_tecnica/ROB_V20_0005/1/Prim%25C3%25A1rio+Hydroviplite-ficha_tecnica.pdf) (application, drying, mould).
- CIN, sheet 18105 on [idoctec.cin.com](https://idoctec.cin.com/Home/Document/18105-DEC-SOT-BT-PT): not opened; **not read directly**, so we do not use it.

## FAQ

### How long should I wait before sanding?

The Aguaplast sheets (February 2024) say "after complete drying", with 24 hours per mm for All 4 in. Barbot (2013) gives 2 hours in 2 mm coats and no sanding time.

### Do I need primer after filling?

The Aguaplast Super Fine sheet says it needs no primer before painting, but says to stabilise very absorbent surfaces. Robbialac Hydroviplite works as a sealer and is recoatable in 4 to 6 hours.

### Can I cover mould with filler?

No. The Aguaplast sheet says to clean mould areas and treat them with an antifungal before applying filler.

### What is the maximum thickness?

Per the 2024 sheets, 2 mm for Aguaplast Super Fine and 6 mm for All 4 in.

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Source: https://paredecerta.pt/en/guides/skim-and-fill-walls-before-painting. Independent information, not legal or tax advice.