External Coating & Paint Deterioration

Inspection Requirements

• Inspect all external facades systematically for peeling, flaking, blistering, chalking and mould growth — document affected areas with photographs and record approximate surface areas.
• Conduct an adhesion test on representative areas using a cross-cut tape test or pull-off test — poor adhesion indicates the existing coating must be removed before recoating.
• Assess chalk level on aged paint surfaces using a visual rating — heavy chalking indicates the film has degraded and will not provide a sound base for a new coat.
• Inspect for blistering beneath the paint film — blistering typically indicates moisture trapped between the coating and substrate and requires investigation of the moisture source before recoating.
• Assess moisture content of the substrate using a moisture meter — do not proceed with coating application over damp substrates.
• Identify the existing coating system type where possible — solvent-borne vs water-borne, acrylic vs epoxy — to inform compatibility selection for the recoating system.
• Inspect all render, masonry and concrete surfaces beneath the coating for cracking, spalling, hollow areas and substrate defects — these must be repaired before coating is reinstated.
• Inspect all facade penetrations, control joints and window and door perimeters for sealant condition concurrent with the coating inspection — these must be resealed as part of any recoating programme.
• Check for rust staining through the paint film — this may indicate corroding embedded lintels, ties, fixings or reinforcement requiring investigation and treatment before recoating.
• In coastal or industrial environments, assess the degree of salt or chemical contamination using a Bresle patch test or equivalent — contamination must be removed before new coatings are applied.

Typical Repair Methodology

Durable recoating requires correct surface preparation above all else. A high-quality coating applied over a poorly prepared, damp or defective substrate will fail prematurely regardless of the product selected. Substrate repair, moisture testing and removal of all delaminated film must be completed before any primer or topcoat is applied.

1. 01.Conduct a full facade inspection including adhesion testing, moisture readings and substrate assessment before preparing the recoating scope of works.
2. 02.Identify and repair all underlying substrate defects — render cracks, brickwork repointing failures, concrete spalling, failed sealants and corrosion — before commencing any coating application.
3. 03.Allow all substrates to dry to below the coating manufacturer's maximum permissible moisture content — typically 12–16% for render and concrete substrates.
4. 04.Pressure wash all exterior surfaces at a minimum 2,000 psi to remove chalk, mould, biological growth, dust, salt contamination and loose material.
5. 05.Apply a biocide treatment to all surfaces affected by mould, algae or lichen and allow the manufacturer's specified dwell time before washing off — do not paint over live biological growth.
6. 06.Remove all peeling, flaking and delaminated paint by scraping, wire brushing or mechanical preparation — new coatings must not be applied over loose or delaminated film.
7. 07.Apply a suitable primer or sealer appropriate to the substrate — alkali-resistant primer on new render or concrete; penetrating consolidant on friable or chalky substrates; rust-inhibiting primer on any exposed metal or corroding embedded elements.
8. 08.Apply a minimum of two full coats of a quality exterior acrylic paint, or a specialist elastomeric or texture coating where substrate movement, crack-bridging or heavy texture is required — follow the manufacturer's overcoating intervals.
9. 09.Apply a clear silicone or siloxane water-repellent impregnant to exposed masonry surfaces where the substrate is to be left unpainted but requires protection from moisture and salt ingress.
10. 10.Inspect and reseal all penetrations, control joints, window perimeters and door perimeters before completing the coating work — the sealant and coating must be compatible and installed in the correct sequence.
11. 11.Conduct a final inspection on completion to confirm full coverage, correct film build, absence of holidays, sags, brush marks and runs.
12. 12.Record the coating system, product names, batch numbers, application date and substrate conditions in the strata maintenance register.