How Much Sealant for Windows?
Quick Answer
Approximately 3 metres of sealant per window
Based on: a standard 1200 × 1200mm window with external frame seal. One 310ml cartridge covers 8–10 linear metres.
How We Calculated This
Window sealant is applied around the external perimeter where the frame meets the masonry or render. For a standard window:
- Perimeter: (1.2m + 1.2m) × 2 = 4.8m
- Less the sill (usually sealed separately or left for drainage): ~1.2m
- Effective sealant run: approximately 3–3.6m per window
How Many Windows per Cartridge?
A standard 310ml cartridge of silicone or hybrid sealant produces a bead approximately 6–8mm wide × 6mm deep. At this bead size:
- 310ml cartridge: 8–10 linear metres
- Typical house (8–12 windows): 3–5 cartridges
Which Sealant Type?
- Low-modulus silicone: Most common for uPVC and aluminium frames. Stays flexible.
- Hybrid polymer (MS polymer): Paintable, UV-resistant, good adhesion to most surfaces.
- Butyl sealant: Used for sealed units and secondary glazing.
- Acrylic sealant: Interior use only — not weatherproof for external frames.
Tips
Always remove old sealant before reapplying. Use a sealant removal tool or Stanley knife. Apply painter’s tape either side of the joint for a clean finish, and smooth the bead with a wet finger or profiling tool before it skins over (within 5–10 minutes for silicone).
Last updated: April 2026. Coverage figures are typical — always check the manufacturer’s data sheet for your specific product.