Description
Arbomast GP Sealant – Traditional Oil Based Pointing Sealant
Arbomast GP sealant is a one-part oil based sealant designed for traditional pointing, perimeter sealing and joint sealing in construction applications. Commonly used for timber frames, concrete panel joints and external sealing work, Arbomast GP forms a protective surface skin while remaining pliable within the joint for long-term durability.
What Is Arbomast GP Used For?
- pointing sealant
- general pointing sealant
- perimeter joint sealing
Oil Based Sealant for Timber & Concrete
- timber frame sealant
- concrete panel sealant
Key Features
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Reliable sealing – Ideal for perimeter sealing of timber frames and joints between preformed concrete panels (e.g., garage construction).
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Overpaintable – Can be painted after application (always pre-test for compatibility).
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Durable & flexible – Maintains pliability for years, ensuring dependable results.
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Good chemical & UV resistance – Suitable for most exterior environments.
Not recommended for:
Expansion joints or those subject to high movement
Use against natural stone
Interior applications
Arbomast GP vs Modern Sealants (Comparison Chart)
Choosing between Arbomast GP and modern sealants depends on whether your job needs traditional pliable pointing or higher movement / faster curing modern performance. Arbomast GP is an oil-based classic suited to stable external joints, while hybrid, silicone and polyurethane sealants are usually better for modern dynamic construction joints.
| Feature | Arbomast GP | Hybrid Polymer Sealant | Silicone Sealant | Polyurethane Sealant |
|---|---|---|---|---|
| Main Type | Oil-based mastic | MS / Hybrid polymer | Silicone elastomer | PU adhesive sealant |
| Best For | Traditional pointing, timber frames, concrete panel joints | General construction sealing, paintable external joints | High movement weatherproof joints, glazing | Strong flexible bonding + sealing |
| Movement Capability | Low to moderate | Medium to high | High | Medium |
| Paintable | Yes (test first) | Yes (most grades) | Usually no | Usually yes |
| Skin / Cure Speed | Slow skinning, remains pliable internally | Faster cure | Fast skin | Medium |
| UV Resistance | Good | Good to very good | Excellent | Good |
| Adhesion Strength | Moderate | Good | Moderate | High |
| Suitable for Timber Frames | Excellent | Good | Fair | Good |
| Suitable for Expansion Joints | No | Often yes | Yes | Sometimes |
| Interior Use | Not recommended | Yes | Yes | Yes |
| Ease of Tooling | Traditional workable mastic | Easy | Easy | Medium |
| Longevity | 10+ years typical | Strong modern durability | Excellent outdoors | Strong durability |
🧱 When Arbomast GP Wins
Choose Arbomast GP when you need:
- Traditional perimeter sealing around timber frames
- Precast concrete panel joints / garages
- A classic overpaintable mastic look
- A pliable seal that stays workable over time
- Lower movement external joints
🚀 When Modern Sealants Win
Choose a modern sealant when you need:
- Faster curing and quicker handover
- Higher joint movement capability
- Interior applications
- Stronger adhesion to varied substrates
- Long-life facade / glazing performance
Application Instructions
Joint Preparation
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Surfaces must be clean, dry, and free from dust, grease, or contamination.
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Degrease with a suitable ARBO® Cleaner.
Joint Backing
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Use an appropriate joint filler (e.g., closed-cell polyethylene foam) to achieve correct joint depth.
Sealant Application
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Apply Arbomast GP from 380ml polyethylene cartridges using an ARBO® Caulking Gun.
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Prepare and apply in line with BS 8000-16:1997 + A1:2010 (British Standard for sealing building joints).
Technical Data
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Tack-Free Time (20°C / 65% RH): ~24 hours (forms skin in approx. 14 days, depending on conditions)
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Application Temperature: +5°C to +40°C
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Service Temperature: -25°C to +70°C
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Movement Accommodation:
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Butt joints (tension/compression): 10%
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Lap joints (shear): 20%
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Chemical Resistance: Resistant to most dilute acids and alkalis
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UV Resistance: Good (slight yellowing may occur on light colours)
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Service Life: 10+ years (improved by overpainting)
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Colours: Grey, Black, White
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Joint Dimensions:
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Width: 6–20mm (single application)
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Depth: 10mm (porous), 6mm (non-porous), max 20mm
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Width/depth ratio: 2:1 (butt joints), 1:1 (lap joints)
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Packaging & Storage
Supplied in 380ml polyethylene cartridges. Store in a cool, dry place away from direct sunlight. Keep cartridges sealed until use.
Health & Safety
Use only in well-ventilated areas. Avoid skin and eye contact. Always consult the product’s Safety Data Sheet (SDS) before use.
