Southwark has one of the largest concentrations of social housing in London, with estates ranging from inter-war low-rise blocks to post-war system-built towers and 1960s/70s deck-access developments. Fire compartmentation — the principle of containing fire and smoke within defined boundaries — is a critical safety measure in all of these building types, yet decades of maintenance, alteration and ageing have left many blocks with significant compartmentation deficiencies.
Compartmentation is the primary passive fire protection measure in residential buildings. It works by dividing the building into fire-resistant compartments — typically individual flats, stairway enclosures and service risers — so that a fire in one compartment is contained and does not spread to others. This allows residents in unaffected flats to stay put safely while the fire service tackles the fire, and provides protected escape routes for those who need to evacuate.
In Southwark's housing estates, effective compartmentation is essential because of the building types involved (many are medium- to high-rise with single stairway access), the construction methods used (including large-panel system buildings with inherent compartmentation weaknesses), and the vulnerability of many residents. A breach in compartmentation can allow fire and smoke to spread rapidly, with potentially catastrophic consequences.
Southwark's social housing stock includes several distinct building types, each with characteristic compartmentation challenges. Post-war system-built towers (1950s–1970s) often have large-panel construction with potential weaknesses at panel joints. Deck-access blocks feature open or semi-open access ways that may compromise the protected escape route. Low-rise walk-up blocks of the inter-war period have solid construction but frequently suffer from decades of unsealed service penetrations. More recent stock (1980s onwards) is generally better compartmented but may still have issues arising from maintenance works or alterations.
We carry out fire compartmentation surveys across Southwark and have detailed experience of the borough's housing stock.
The most frequently encountered breach in Southwark's housing estates is unsealed service penetrations through compartment walls and floors. Over decades, gas, water, electrical and telecommunications services have been installed, modified and replaced, with each intervention potentially creating a new penetration through a fire-resistant barrier. Where these penetrations are not properly fire-stopped with intumescent sealant, fire batts or collars, they create pathways for fire and smoke to pass between compartments.
Fire doors are a critical element of compartmentation, yet many flat entrance doors and communal doors on Southwark's housing estates do not meet the required FD30S standard. Common issues include missing or damaged intumescent strips and smoke seals, missing or broken self-closing devices, excessive gaps between the door and frame, damage from forced entry, and replacement with non-certified doors. A systematic fire door inspection programme is essential.
Service risers and shafts run vertically through the building and, if not properly compartmented, can act as chimneys that draw fire and smoke from floor to floor. In many of Southwark's older blocks, riser cupboard doors are non-compliant or missing, fire stopping within the riser has been disturbed by maintenance works, and the riser construction itself may not achieve the required period of fire resistance. Riser remediation is often one of the most complex and costly elements of a compartmentation improvement programme.
Many system-built and concrete-framed blocks have concealed voids in the ceiling and floor construction that can allow fire to spread laterally between flats. These voids may have been compartmented at the time of construction using cavity barriers or fire stopping, but subsequent alteration or deterioration can compromise their integrity. Identifying and assessing these concealed breaches typically requires intrusive inspection, which adds to the survey scope but is essential for a thorough compartmentation assessment.
The first step is a comprehensive compartmentation survey of the estate, carried out on a block-by-block basis. The survey identifies all compartmentation breaches, categorises them by risk and provides a prioritised remediation schedule. For large estates, a phased approach is typically needed, with the highest-risk blocks addressed first. The survey output should integrate with the estate's fire risk assessment programme and any Building Safety Act obligations.
Compartmentation remediation works on housing estates require careful procurement. The contractor must have demonstrable competence in passive fire protection, use third-party-certified products and provide detailed completion records. For housing associations, the works may need to be procured through existing frameworks or through a competitive tendering process that meets the organisation's governance requirements. We can assist with specification, procurement and quality oversight of remediation programmes.
Compartmentation works on occupied housing estates require access to individual flats, which presents logistical challenges. Clear communication with residents about the scope, purpose and timing of the works is essential. Housing associations should plan for access refusals and have escalation procedures in place. The works themselves are typically carried out with residents in situ, but some may require temporary relocation where the scope is extensive. A well-planned engagement strategy reduces disruption and improves access rates.
The most common breaches include unsealed service penetrations through compartment walls and floors, missing or deteriorated fire stopping around riser cupboards and service shafts, non-compliant fire doors, gaps and voids in ceiling and floor constructions, and breaches introduced by maintenance works or tenant alterations that were not properly fire-stopped.
Best practice is to carry out a comprehensive compartmentation survey every three to five years, with interim inspections following any significant maintenance or alteration works. For buildings over 18 metres, the Building Safety Act 2022 requires ongoing assessment. The Regulator of Social Housing expects registered providers to maintain current fire safety information across their stock.
The responsible person under the Regulatory Reform (Fire Safety) Order 2005 is typically the housing association, local authority or registered provider. They must ensure compartmentation is maintained, fire risk assessments are current and significant findings are addressed. For buildings under the Building Safety Act 2022, the Accountable Person has additional duties including the preparation of a safety case.
Costs vary significantly. Fire stopping remediation for a typical medium-rise block of 30 to 50 flats may cost £50,000 to £150,000 or more. Fire door replacement programmes add to this. For large estates with multiple blocks, budgets can run into millions. Early survey and prioritisation are essential to manage costs and direct resources to the highest-risk areas first.
Comprehensive compartmentation surveys for housing associations and registered providers.
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