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ARBOMAST GP - Oil-Based Sealant for Timber Frame and Precast Concrete Panel Joints

ARBOSEAL PRO® ARBOMAST GP is a one-part oil-based sealant for general pointing and sealing of joints in traditional construction. It forms a surface skin whilst the bulk of the material remains pliable for several years. Designed for perimeter sealing of timber frames and joints between preformed concrete panels, it is overpaintable and provides a 10+ year service life.

Specify Arbomast GP

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Unique properties of Arbomast GP

Arbomast GP provides a cost-effective, overpaintable sealing solution for timber frame perimeter joints and precast concrete panel joints in traditional construction.

  • Oil-based general purpose sealant — cost-effective solution for traditional construction jointing

  • Overpaintable — compatible with most exterior paint systems (pre-test recommended)

  • Remains pliable in the bulk — accommodates minor movement in service

  • Suitable for exterior perimeter sealing of timber frames and precast concrete panel joints

  • Available in Grey, Black, and White to match common construction substrates

  • 10+ year service life — improved by overpainting; complies with BS 8000-16

Technical Specifications & Downloads

DescribtionPerformance
Tack Free Time at 20°C/65 % RH: 24 hours, Arbomast GP forms a skin after approximately 14 days depending upon atmospheric conditions.
Application temperature:+5˚C to + 40˚C
Service temperature:
-25°C to + 70°C
Chemical Resistance: Resistant to most dilute acids and alkalis.
UV resistance: Good, but slight yellowing of light colours may be observed.
Service Life:10 years + (resistance to ageing can be improved by overpainting).
Movement Accommodation:Butt joints (movement in tension and compression): 10%
Lap joints (movement in shear): 20%
Colours:Grey, Black, White

Associated Products

Arbomast BR - ARBOSEAL Pro®

A ready-to-use butyl rubber mastic sealant for use in construction and glazing applications.

Arbocaulk - ARBOSEAL Pro®

An acrylic-based paintable interior sealant for low-movement joints in internal applications.

Arbosil HM - ARBOSEAL Pro®

A high-modulus neutral cure silicone sealant for structural and high-performance glazing applications.

Arbosil 1081 - ARBOSEAL Pro®

Acetoxy cure silicone sealant recommended for sanitary and internal applications.

Arbosil ONE - ARBOSEAL Pro®

A one-part neutral cure low modulus silicone sealant developed for demanding construction applications.

Frequently Asked Questions

1

Why choose ARBOSEAL Pro® Arbomast GP for timber frame and concrete panel sealing?
Arbomast GP is an oil-based sealant formulated specifically for traditional construction applications where a paintable, general-purpose sealant is required. Its pliable bulk accommodates the minor movement typical of timber frame and precast concrete panel joints, while its overpaintable surface allows a seamless transition to the decorated finish. It is the practical, cost-effective choice for perimeter sealing in domestic and light commercial construction where the joint will be concealed by paint.
 

2

What are the key benefits of ARBOSEAL Pro® Arbomast GP?
Arbomast GP provides a simple, overpaintable sealing solution with a 10+ year service life that can be extended further by overpainting. With a tack-free time of 24 hours, a 10% movement accommodation, and availability in Grey, Black, and White, it covers the most common requirements for timber frame and concrete panel perimeter sealing. Supplied in 380 ml cartridges for the ARBO® Caulking Gun, it is quick and efficient to apply. Application should be in accordance with BS 8000-16:1997 + A1:2010.
 

3

What is the ARBOSEAL Pro® range?
The ARBOSEAL Pro® range is a comprehensive portfolio of professional-grade sealants manufactured by Adshead Ratcliffe under the ARBO® brand. The range covers silicone, modified polymer, polyurethane, polysulphide, epoxy, acrylic, butyl, and oil-based sealant technologies, providing a complete solution for sealing, bonding, and jointing across all types of construction projects — from glazing and cladding to flooring, facades, and secure environments.
 

4

Which ARBOSEAL Pro® sealant is right for my application?
Product selection depends on the substrate type, joint movement, environmental exposure, and performance requirements. Neutral cure silicones (e.g. Arbosil LMS, Arbosil 1096 S) suit glazing and perimeter sealing. High-modulus options (e.g. Arbomeric MP20) handle structural joints. Polysulphides (e.g. Arbokol AG2, Arbokol 2150) provide chemical resistance for floors, roofs, and water-retaining structures. Epoxy sealants (e.g. Arbokol SECURE, Arbokol 1025 SP) deliver hard-wearing seals for secure environments and pool applications. Contact ARBO® Technical Services for specific guidance.
 

5

What surface preparation is required before applying an ARBOSEAL Pro® sealant?
All joint faces must be clean, dry, and free from dust, oil, grease, loose material, and previous sealant residues. For porous substrates such as concrete and brickwork, the application of an ARBO® primer is recommended to maximise adhesion. Always consult the product-specific Technical Data Sheet (TDS) for primer and cleaner recommendations. Application should be carried out in accordance with BS 8000-16:1997 + A1:2010.
 
 

6

Where can I find technical documentation for ARBOSEAL Pro® products?
Technical Data Sheets (TDS), Safety Data Sheets (SDS), and Declarations of Performance (DoP) for all ARBOSEAL Pro® products are available for download on each individual product page at arbo.co.uk. The full ARBO® Product Catalogue is also available for download. For further technical support or specification advice, contact ARBO® Technical Services directly.

Explore the ARBO® Product Family

Sealants

Sealants for reliable movement joint, perimeter and weatherproof sealing in a wide range of applications.

Weather Protection

Effective weather sealing solutions for interface applications, penetration sealing and structural joints.

Adhesives

Bonding solutions for secure and durable adhesion across façade and construction substrates.

Accessories

Caulking Guns, Nozzles, Knives, Scrapers, G Clamps etc.

Find your contacts

Regardless of whether you are an architect and planner, property developer, industry specialist, distributor, applicator or specifier – if you have any questions about our products, services or specific construction projects, please feel free to contact the CARLISLE® contact person in your area with your technical questions. Our experts will be happy to advise you.

Here's how to do it: Simply enter your postcode in the search field of the map

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Main Applications

Arbomast GP is the specified choice for perimeter sealing of timber frames and joints between preformed concrete panels in traditional construction.

Timber Frame Perimeter Sealing

Sealing the perimeter joints between timber frames and masonry in traditional domestic construction.

Precast Concrete Panels

Sealing joints between preformed concrete panels, for example in garage construction.

Traditional Construction Pointing

General pointing and sealing of low-movement joints in brick, block, and masonry construction.

Overpaintable Joints

Applications where a sealant that accepts exterior paint coatings is required for a finished appearance.

ARBOMast BR - ARBOSeal Pro®
Read more
ARBOCaulk - ARBOSeal Pro®
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ARBOSil HM - ARBOSeal Pro®
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ARBOSil 1081 - ARBOSeal Pro®
Read more
ARBOSIL ONE - ARBOSEAL Pro®
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ARBOSEAL Pro Range
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Accessories
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Arbobond Pro
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Accessories
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