External Plastering: Complete Method, Costs & Quality Control (London Guide)

External plastering is more than a “skim and go.” Done right, it protects your building envelope, delivers the façade finish you want, and prevents water ingress for years. Below is our AmtaarGC field-tested workflow, aligned with classic method statements for multi-storey buildings, and adapted for London sites (tight access, mixed substrates, and year-round weather).

What Is External Plastering?

External plastering (rendering) is the multi-layer build-up applied to exterior blockwork or concrete to provide weather protection and a consistent finish ready for paint or a pressed/tyrolean texture. On mixed substrates (block to columns/beams/slabs), we reinforce junctions to avoid cracking and ensure a uniform, durable façade.

Our Site Sequence (AmtaarGC)

1. Access & Safety

• Erect and tie scaffolding with handrails and safe access; audit before works begin. 

2. Substrate Prep

• Clean surfaces; hack off fins; remove oils/grease/dust by scrubbing.
• Fill chases/holes around M&E; fix services before plastering.
• Reinforce all block-to-concrete junctions with approved lathing/mesh using slurry. 

3. Key Coats & Base Render

• Pre-wet surfaces.
• Apply 3–5 mm 1:3 cement:sand coat including waterproofing additive per data sheet.
• Same day, dash a slurry key (≈400 kg cement to 1.0 m³ clean sand) pneumatically or manually.
• Cure with water for ≥24 hrs.
• Apply main plaster/render 10–20 mm (min 10 mm) at 1:4 cement:sand; cure ≥48 hrs. 

4. Finish Options (Tyrolean/Pressed)

• First tyrolean: 1 part white Portland cement : 2 parts fine aggregate, applied uniformly.
• Second/final tyrolean: also 1:2 (white cement:fine aggregate), with colour additives to approved sample, then mechanically flattened to a pressed finish if specified. Cure ≥48 hrs.
• Form sloped horizontal joints where plaster meets stonework; waterproof those junctions. 

5. Details, Protection & QA

• Install marble/stone cills after plasterwork; make good as needed.
• Keep sites clean; do not re-temper set mixes.
• QC with straight edges, plumb lines and checks for verticality/horizontal control using screeds/spacers.
• Skilled trades throughout; protect adjacent works. 

Typical Build-Ups We Deliver

• Traditional cement:sand render with waterproofing additives and tyrolean/pressed finish.
• Reinforced junctions at block/RC interfaces to control cracking.
• Weather-managed curing and staged program to suit London conditions.

What Drives Cost?

• Access (full-height scaffold vs towers), substrate condition, junction reinforcement, finish complexity (e.g., two-stage tyrolean with colour), and QA/defect prevention (cure times, weather protection). We scope these items upfront so there are no surprises.

Common Failure Points We Avoid

• Skipping the slurry key or curing windows → poor adhesion and hairline cracking.
• Not reinforcing junctions → reflective cracks at columns/beams/slabs.
• Re-tempering partially set mixes → weak, patchy render. 

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