Painting and Coating Works

Surface preparation must comply with DIN 18363 (VOB/C) and the applicable BFS Merkblatt guidelines. The substrate must be assessed for type, condition, adhesion of existing coatings, moisture content, alkalinity (pH) and surface contamination. BFS Merkblatt No. 1 covers assessment of substrates for coating works. Old coatings must be tested for adhesion and compatibility with the new coating system. New plaster and concrete must be tested for alkalinity (pH < 10) and moisture before coating. DIN 18363 Section 3 specifies the preparation requirements by substrate type.

1. Identify substrate type and assess condition — check for cracks, efflorescence, mould, algae and loose material

2. Test adhesion of existing coatings using cross-cut test per EN ISO 2409 or pull-off test per EN ISO 4624

3. Measure substrate moisture — concrete maximum 4 CM-%, plaster maximum 2-3 CM-%, depending on coating system

4. Check pH of new plaster and concrete — must be below pH 10 for standard dispersion coatings per BFS Merkblatt No. 1

5. Verify that all surfaces are clean, dust-free and primed with appropriate system primer before coating application

- Painting over damp substrates causing blistering and peeling of the coating

- New plaster with high alkalinity (pH > 10) causing saponification of non-alkali-resistant paints

- Insufficient cleaning — dust and efflorescence preventing adequate adhesion

- Incompatible primer used for the substrate type or the topcoat system

Interior wall and ceiling paints must be classified in accordance with EN 13300. The classification includes wet scrub resistance (Class 1 to Class 5, replacing the old washability/scrubbability distinction), contrast ratio (hiding power), and gloss level. Class 1 offers the highest wet scrub resistance and is suitable for high-traffic areas. Class 3 is the standard for residential use. The number of coats, spreading rate and dry film thickness must follow manufacturer specifications. BFS Merkblatt No. 26 provides guidance on interior coating quality assessment.

1. Verify paint classification per EN 13300 — wet scrub resistance class appropriate for the room use (Class 1-2 for high traffic, Class 3 for standard residential)

2. Check contrast ratio (hiding power) — Class 1 or 2 ensures adequate coverage in typically two coats

3. Inspect for uniform appearance — no roller marks, brush marks, curtains, drips or uneven texture under diffused and grazing light

4. Verify coating coverage — ensure all surfaces are uniformly coated with no misses or thin spots visible at edges and corners

5. Confirm colour consistency — compare applied colour to specified RAL, NCS or manufacturer colour reference

- Low wet scrub resistance paint (Class 4-5) used in kitchens or corridors where Class 1-2 is required

- Insufficient number of coats resulting in poor hiding power and substrate showing through

- Roller marks and lap marks visible due to incorrect application technique or paint viscosity

- Colour variation between walls due to mixing paint from different batches

Exterior masonry and concrete coatings must comply with EN 1062-1 classification for water permeability (W1-W3), water vapour transmission (V1-V3), crack-bridging ability (A0-A5) and CO2 permeability. German practice follows BFS Merkblatt No. 6 for facade coating systems. The coating system must be compatible with the substrate and environmental exposure — e.g. high wind-driven rain zones require W3 water permeability class. Silicone resin paints or silicate paints are preferred for mineral substrates in Germany due to their high vapour permeability.

1. Verify coating classification per EN 1062-1 — water permeability class (W), vapour transmission class (V) and crack-bridging class (A) match specification

2. Check system compatibility — primer, intermediate coat and topcoat must be from a compatible system per manufacturer specification

3. Measure dry film thickness at multiple locations using non-destructive methods — compare to manufacturer's minimum requirements

4. Inspect for defects — no sagging, curtaining, pinholing, streaking or missed areas on the completed facade

5. Verify weather conditions during application — temperature between 5°C and 30°C, no direct sunlight on hot days, no rain expected within the drying period

- Coating with low vapour permeability (V3) applied over damp masonry, trapping moisture and causing blistering

- Application in unsuitable weather — rain, frost or direct sun causing premature drying, cracking or wash-off

- Insufficient film thickness resulting in reduced weather protection and premature coating failure

- Silicate paint applied over non-mineral or previously coated substrates without proper preparation

- Crack-bridging coating not specified for substrates with existing or expected cracks

Coatings for exterior wood must comply with EN 927 series — EN 927-1 (classification), EN 927-2 (performance specification) and EN 927-6 (artificial weathering test). DIN 18363 Section 3.4 covers wood coating works. Coating systems are classified as opaque (film-forming), semi-transparent (stain) or transparent (clear). Wood moisture must be below 20% before coating application. End-grain sealing, back-priming and edge rounding (minimum 2 mm radius) are essential for durability. BFS Merkblatt No. 18 provides detailed guidance on wood coating systems.

1. Measure wood moisture content — must be below 20% (ideally 12-15% for joinery) before coating application

2. Verify that end-grain surfaces are sealed to prevent excessive moisture uptake

3. Check edge rounding — minimum 2 mm radius on all edges per BFS Merkblatt No. 18 for adequate coating build-up

4. Inspect coating uniformity — no runs, drips, brush marks, missed areas or insufficient film thickness on any surface

5. Confirm that all surfaces are coated including concealed faces (back-priming) to prevent differential moisture uptake

- Wood too wet at time of coating, leading to blistering and peeling within the first year

- End grain left unsealed, allowing rapid moisture uptake and premature coating failure at joints

- Sharp edges not rounded, resulting in thin coating that breaks down quickly under UV and weather exposure

- Back surfaces and concealed areas left uncoated, causing differential moisture movement and warping

The finished coating quality must comply with DIN 18363 acceptance criteria and BFS Merkblatt No. 25 (assessment of surface quality). The assessment is conducted under normal lighting conditions — diffused daylight or artificial light viewed perpendicular to the surface from a distance of approximately 1 m. Grazing-light inspection (Streiflicht) is only applicable if explicitly agreed in the contract. The coating must be free from visible defects including runs, drips, curtains, pinholes, brush marks, roller stipple and colour variation. Clean lines at colour boundaries and masking edges are required.

1. Inspect all surfaces from 1 m distance under normal diffused lighting — no visible runs, drips, sags, misses or colour variations

2. Check colour boundaries and masking lines — clean straight lines with no bleed-through or ragged edges

3. Verify that adjacent surfaces (frames, glass, fittings) are free from paint splatter and overspray

4. Inspect finish uniformity — consistent sheen level across all coated surfaces, no patchy or glossy spots

5. Check that the specified number of coats has been applied by measuring dry film thickness or reviewing application records

- Visible roller marks and lap lines due to incorrect technique or poor quality tools

- Paint splatter on windows, frames and fittings due to inadequate masking protection

- Colour variation between walls or sections due to inconsistent coat thickness or different batches

- Patchy gloss level caused by uneven absorption of substrate or inconsistent application thickness

Paints and coatings must comply with the ChemVOCFarbV (Chemikalien-Verbotsverordnung — Chemical VOC Paint Ordinance), which implements EU Directive 2004/42/EC on VOC emissions from paints and varnishes. The ordinance sets maximum VOC content limits by product category (e.g. interior matt wall paint: 30 g/l, exterior masonry paint: 40 g/l). Products must be labelled with their VOC content and category. For enhanced indoor air quality, the German Committee for Health-related Evaluation of Building Products (AgBB) scheme and Blue Angel (Blauer Engel RAL-UZ 102) certification provide additional guidance.

1. Check product labels for VOC content declaration — verify values are within ChemVOCFarbV limits for the product category

2. Verify product category classification per ChemVOCFarbV Annex II matches the intended application

3. Review technical data sheets for AgBB-evaluated or Blue Angel (Blauer Engel) certified products where indoor air quality is a requirement

4. Confirm that solvent-based products are not used where water-based alternatives are specified in the contract

5. Check ventilation provisions during and after application — adequate air exchange for VOC dissipation per occupational health requirements

- Product VOC content exceeds ChemVOCFarbV category limits — non-compliant product delivered to site

- Solvent-based coatings used indoors where specification or client requirements call for low-VOC products

- Missing VOC content labelling on product containers making compliance verification impossible

- Inadequate ventilation during interior coating application leading to health risks and slow VOC off-gassing