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J-SEAL® MS1 Modified Silicone Joint Sealant

Product Description

CORKJOINT J-SEAL® MS1 Modified Silicone Joint Sealant is a fast curing one part modified silicone based joint sealant, which cures on absorption of atmospheric moisture to form a firm and flexible seal for moderate movement joints, construction joints and control joints. J-Seal® MS1 can be used in both horizontal and vertical applications.


  • Highly resilient with excellent recovery characteristics
  • Provides a permanent and uniform water-resistant seal
  • Excellent adhesion to most building substrates
  • Weather and UV resistant
  • Non-biodegradable
  • Non-toxic once cured. Can be used in potable water environments
  • Easy to apply, one component sealant. No mixing required
  • Over painting can be done with dispersion based paints (acrylic, vinyl

Areas of Application

  • Construction and expansion joints in concrete slabs and walls
  • Precast concrete joints
  • Brick and masonry expansion joints
  • Perimeter caulking (windows, doors, aluminium frames)
  • Structural glazing & curtain wall joints
  • Parapet wall joints

Note : The product’s design and performance, its intended use, installation and final confirmation and approval for use, must be provided by the project’s Design Engineer and Project Manager.

Joint Design Geometry

The width of the joint should be a minimum of 4 times the anticipated movement but within the maximum width requirements. Joints with cyclic movement should have a width to depth ratio of 2:1 and 1:1 for static joints. The joint depth shall not exceed the width.

The joint width and depth should be maintained as suggested:

5 mm (Minimum)
25 mm (Maximum)

5 mm (Minimum)
15 mm (Maximum)

Note : Wider joint widths may be applicable but check with CORKJOINT for verification.
Final joint sizes/geometry should be verified and approved by the Project’s Design Engineer.


Below is the calculation formula for quantity required for coverage:

Width (mm) x Depth (mm) x Length (m)  / 1000 = litres

20mm x 10mm x 100m/1000 = 20 litres

Note : Calculation based on theoretical coverage. Actual material consumption at site will vary depending upon final joint size and wastage etc.

Typical Installations

JOINT PREPARATION  – The joint edges must be clean, dry and free from oil, loose particles, cement laitance and other contaminants, which may affect the adhesion. A thorough wire brushing, grinding, sand blasting or solvent cleaning, may be required to expose a clean and sound substrate. When applied on glazed surfaces like ceramic or terrazzo tiles or porcelain enamel joint surfaces, the glaze should be removed by abrading with sandpaper or wire brush.

PRIMING – After preparing the surface as above and making sure the surface is dry, for concrete and masonry surfaces, apply one layer of J-Seal® Primer N49 on each side of the joint receiving the sealant. When applying on aluminium and metal surfaces, ensure the surface is cleaned of all lacquer or protective coatings. Metal, galvanized, copper and stainless-steel surfaces shall be primed with J-Seal® Primer N40. The primer shall be applied by a brush in a thin coat application and shall be allowed to become tack free prior to the application of the sealant. For obtaining a clean and neat finish, masking tape should be applied on both edges of the joint before the application of the primer or the sealant and shall be removed once the sealant installation is complete.

BACKING MATERIAL – A bond breaking backing rod shall be inserted into all movement joints to avoid three-sided adhesion or bond breaking tape may be applied to joints where the depth does not allow the application of the backing rod. If the fillerboard is closed-cell polyethylene then no backing material is required as the sealant will not bond to the surface of the fillerboard. 

APPLICATION – J-Seal® MS1 is available in a ready to use self-contained sausage which can be loaded into a barrel gun. Start extruding the sealant into the joint firmly by maintaining an even pressure on the trigger of the gun. On vertical joints, sealant extrusion shall start from the bottom of the joint and continue to the top. Once the sealant has been installed, a suitable rounded tool can be used to achieve a smooth concave profile. Do not use soapy water solution to smoothen the surface. Any masking tape applied should be removed immediately after the sealant has been
applied and the desired finish has been achieved. 

Note : Joint sealant can only be applied for use on concrete or cement after 28 days of curing of the substrate. 


J-Seal® MS1 is not recommended for:

  • Overhead joints
  • Movement joints having MAF > 25%
  • Damp and contaminated surfaces
  • Asphalt pavements or any material containing bitumen
  • Over painting with enamel or rigid paints (paint compatibility with sealant shall be checked prior to painting)
  • External application in white/off white will result in yellowing on exposure to UV
  • Use in chlorinated water such as swimming pools & spas
  • Immersion in salt water
  • Applied in joints wider than 25mm
  • Applied in joints less than 5mm in width and depth
  • Use for glazing applications

Packaging and Supply

J-Seal® MS1 – 600ml (20 sausage/carton)
J-Seal® N49 – Primer 1ℓ pail
J-Seal® N40 – Primer 1ℓ pail
Ancillaries & Equipment – Jointflex® Backer Rod (Closed Cell Polyethylene) Sealant Barrel Gun

Storage & Shelf Life

Store in a cool, dry place and keep away from all sources of heat and sunlight. In tropical or hot climates, store in air-conditioned rooms. The shelf life is up to 12 months in un-opened condition and if stored as per recommendations. Excessive exposure to sunlight, humidity and UV will result in the deterioration of the quality of the product and reduce its shelf life.


Remove all excess sealant with a scraper. Any spillage can be cleaned using solvent or xylene. Clean all tools and equipment using similar solvents immediately after the tooling. Hardened materials can be removed mechanically only.

Written Specification

Where shown in the drawings, the joint sealant must be J-Seal® MS1 polyurethane joint sealant as supplied by CORKJOINT. The application/installation of the product must be in accordance with the manufacturer’s recommendations and J-Seal® MS1 Primer must be used in conjunction with the application of the joint sealant.

Refer to Product Brochure for more details.

Health & Safety Information

Do not apply primer near smoke or naked flame. In case of fire, extinguish with carbon dioxide, dry chemical or foam fire extinguisher.

As with all construction chemical products caution should be exercised. Protective clothing such as gloves and goggles should be worn. Treat any splashes to the skin or eyes with fresh water immediately. Should any of the products be accidentally swallowed, do not induce vomiting, but call for medical assistance immediately.

In confined spaces or in still air conditions, the use of a ventilation fan or suitable respirator should be used, and the advice and approval of the Site Safety Supervisor is essential. For further information or advice on health and safety precautions, safe handling, storage and correct disposal of products, please refer to the most recent product Safety Data Sheet (SDS), which is available upon request.


The information and the recommendations relating to the application and end use of this product are given in good faith and are based on the information provided by the manufacturer of the product and/or the Company’s current knowledge and experience in connection with the product when properly stored, handled and applied under normal conditions and no liability of final function at the job site is assumed. In practice, the differences in materials, substrates and actual site conditions are such that no warranty in respect of merchantability of, or fitness for, particular purpose, nor any liability arising out of any legal relationship whatsoever, can be inferred either from this information, or from any written and/or oral recommendations, or from any other advice offered by the Company. The Company also has no express or implied knowledge of any particular purpose for which the product is required and any such information given will not be taken into account in the supply of this product. No responsibility or liability by the Company will be accepted for misuse, misreading or derivation from recommended guidelines in respect of this product and the user shall determine the suitability of the product for his intended use and assume all risks and liability in connection therewith. The information contained in our brochure may change at any time without notice. Any use of this product, J-Seal® MS1, in any application should be approved as suitable for use/application by the Design Engineer and Project Manager.