Mastic

Cable Duct Sealing

GPT provide expert services for multi-cable and pipe transit sealing systems. Mastic sealants provide an effective and simple solution for all fireproof, gastight & water tight duct sealing requirements.

Mastic Cable Duct Sealing

We offer specialist mastic sealing services for cable and pipe duct entries, offering long-lasting protection against water and gas ingress. Our high-performance mastic sealant bonds securely to both cables and duct walls, forming a flexible, gas and water-tight seal that withstands pressure, movement, vibration, and environmental exposure.

This approach is widely used across utility, industrial, and commercial sectors, particularly where mechanical sealing methods are unsuitable.

Unlike mechanical sealing systems that rely on duct uniformity and ideal conditions, mastic sealant adapts to a wide range of duct shapes and states of repair. It is particularly effective for retrofitting poorly installed or damaged ducts, and is ideal for situations where cable entries have been left unsealed or compromised by water ingress.

Our team has extensive experience in identifying and resolving non-compliant or deteriorated duct entries using mastic sealing products, tailored to each site’s needs.

We frequently resolve sealing issues in cable ducts that:

Are left completely open or partially blocked
Have deteriorated seals
Were installed without consideration for water or gas ingress
Have irregular, damaged, or misshapen openings

Mastic sealant offers a reliable and cost-effective sealing solution in these complex scenarios, often without the need to remove existing cables or make major civil alterations.

cable duct penetration sealing before mastic sealant

cable duct penetration sealing during mastic sealant

cable duct penetration sealing after mastic sealant

Key Benefits

Water and gas tight even in irregular or damaged ducts
Compliant with DSEAR, WIMES, and ATEX requirements
Proven long-term durability with no expected degradation for 50+ years
Resistant to methane, hydrogen sulphide and chlorine
Resistant to submersion in petrol, diesel and synthetic transmission oils
No framing required
Suitable for trefoil cables and mixed cable arrangements
Easy re-entry for adding cables
Effective flood protection and gas ingress control

Suitable for:

Electrical substations
Water and wastewater treatment facilities
Chemical and hazardous storage areas
Industrial plant rooms and process buildings
Renewable energy and battery storage installations
Sites requiring robust environmental protection or compliance with ISO 14001

Mastic-sealed entries are designed for flexibility. If you need to add or remove cables, a portion of the existing seal can be easily removed and re-sealed without dismantling the entire system.

For projects requiring fire-rated protection, we offer mastic sealing systems that can maintain their integrity for up to 4 hours, in line with BS EN 1366-3 fire resistance testing standards.

All sealing work is subject to GPT’s internal quality assurance procedures. While our mastic sealant provides a highly effective seal in most conditions, certain factors - such as poor underlying infrastructure or extensive duct deterioration - may limit performance*. With extensive industry experience and a commitment to quality, we help protect critical infrastructure while supporting future access and maintenance. For expert advice or to arrange a site assessment, contact our teamtoday.

*Full documentation is provided in a post-installation report, including photographs and recommendations where applicable.