Siderise LGS Linear Gap Seal

Flexible intumescent linear gap seals for sealing junctions between building elements

Versatile protection for junctions 

LGS Linear Gap Seal is a versatile method of sealing junctions between a variety of building elements, preventing the spread of fire. It is made from a compressible flame-retardant treated foam laminate in conjunction with intumescent layers. In a fire, the intumescent expands to prevent the fire spreading through the joint whilst the foam core on the non-fire side remains flexible to accommodate any structural movement. 

Up to 2 hours fire integrity

LGS Linear Gap Seal is available in two widths, both with an Integrity (E) 120 rating

Fast and easy to install

LGS Linear Gap Seal is simply compressed into gap/joint to seal off any gaps up to 20mm

Allows for structural movement

The compressible foam core accommodates different joint widths to allow for structural movement

Related systems

Explore our other solutions developed for specific applications

Learn more

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 providing fire resistance.  

Standard sizes are available to suit voids up to 20mm and provides  2 hours fire resistance (Integrity only).

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 Type Max. Joint Width (mm) Seal Width (mm) Seal Depth (mm) Integrity (E) (mins)

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 with a width to suit the size of the gap required.

The standard sizes are listed in the Fire Resistance 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.

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 Available

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.


Acoustic solutions

We have a range of acoustic treatments for buildings and construction sites. 

Discover more
NBS Logo
Bimstore Logo


Get quick answers to common queries or contact our team for more advice. Your questions answered.

What sizes of LGS Linear Gap Seal are available?

LGS Linear Gap Seals are supplied in 1-metre lengths in widths that either suit maximum gap widths of 10mm or 20mm. For wider gaps, please refer to CW-FS Firestop

How is LGS Linear Gap Seal installed?

LGS Linear Gap Seal is simply compressed into gap/joint such that the multi-layers/banding is visible

Case Studies

Related projects

Siderise is a market leader in the design and development of specialist passive fire.

View all
Contact us

We're here to help you

Talk to us

Call for our main switchboard

+44 (0) 1656 730 833

Ask technical

Email us for technical enquiries

Ask site services

Email us for site support

Complete a form

Complete the form for the right response

Contact us