Technical Data | LGS | Linear Gap Seal | Construction | Products | Siderise

Siderise LGS | Linear Gap Seal – Technical Data

Version: 1.03 - Release Date: October 2022


Siderise LGS Linear Gap Seals are flexible, water-resistant, intumescent linear gap seals that expand when exposed to heat. They provide a versatile means of sealing junctions between building elements against fire penetration. They are maintenance-free and resistant to fungi and vermin. 

The compressible foam core accommodates different joint widths to allow for structural movement whilst additionally meeting requirements for cold smoke seal, thermal and acoustic properties. 

Standard sizes are available to suit voids up to 150mm and provide a 2-hour fire rating. The material can also be used as an effective, adaptable fire stop inside cable trunkings - allowing for the installation of further cables.

Product Description

Siderise LGS Linear Gap Seals are made from an open-cell flame retardant acoustic foam laminate with a graphite intumescent coating containing binders which ensure material flexibility. 

In fire conditions, the seal maintains a close-fitting position to prevent the passage of cold smoke. At the designed temperature, the intumescent coating begins to expand on the fire side of the joint. 

During this reaction, the foam gradually compresses and is replaced by the expanding mass of intumescent graphite. 

The seal retains its flexibility on the non-fire side to accommodate any heat-induced movement of the structural elements. Thus the fire is prevented from penetrating rapidly into the joint.

Fire Performance

Table 1: Fire Resistance to BS 476-20:1987

Product Ref. Max. Joint Width (mm) Seal Width (mm) Seal Depth (mm) Integrity (mins) 
CJ/FS120/012-012 10 12 12 E 120 
CJ/FS120/029-012 20 29 12 E 120 
CJ/FS120/032-020 25 32 20 E 120 
CJ/FS120/053-020 35 53 20 E 120 
CJ/FS120/061-035 50 61 35 E 120 
CJ/FS120/085-040 65 85 40 E 120 
CJ/FS120/090-050 75 90 50 E 120 
CJ/FS120/126-100 100 126 100 E 120 
CJ/FS120/147-125 120 147 125 E 120 
CJ/FS120/170-100 150 170 100 E 120 

Application Technique: Compressed into gap/joint such that the multi-layers/banding are visible.

Siderise LGS Linear Gap Seals are supplied in 1 metre lengths of various widths to suit the size of the gap required. 

The standard sizes are listed in the Fire Rating table above. For void sizes other than those tabled please contact the technical team.

  • Block/masonry/concrete walls and floors shall be at least 150mm thick and have at least the same fire rating as that of the Linear Gap Seal.
  • Block/masonry/concrete gap faces must be within the density range of 450 to 2300kg/m3, and gap faces must be free from loose or flaking material.

Acoustic Performance

Siderise LGS has been tested to EN ISO 10140-2:2010 and achieves:

  • Rw (C;Ctr) : 8 (0;-1) dB
  • DnEw (C;Ctr) : 18 (0:1) dB


Siderise LGS Linear Gap Seals  environmental properties:

  • Halogen-free
  •  Individual components may be separated mechanically; however, they are currently not recyclable.
  •  Please see Safety Data Sheet

    Additional Information

    The following information is available upon request or via download from the website:

    • NBS Specification Clause
    • Standard Details
    • Safety Data Sheet

    Technical Support

    For technical advice or support please contact:

    For Installation Training or Site Inspections please contact:


    The information in this datasheet is believed to be accurate at the date of publication. Siderise has a policy of continuous product improvement and reserves the right to alter or amend the specifications of products without prior notice. Siderise does not accept responsibility for the consequences of using the products described outside of the recommendations within this datasheet. Expert advice should be sought where there is any doubt about the correct specification or installation of Siderise products.

    Published Version: LGS _v1_03_20221027_1711