In building terms a fire wall is a wall built to resist the passage of fire for a stated period, separating one part of a building from another or one building from its neighbour. The commonest problem with them in British housing is in the roof space, where the wall between two houses very often stops at ceiling level and nobody has ever looked.
The main objective of fire compartmentation
The main objective is to confine a fire to the area where it started for long enough that people can leave and the fire service can act. It does that by dividing the building with walls and floors that resist fire, and by protecting every opening in them. A compartment is only as good as its weakest opening, which is why doors, service penetrations and roof voids get the attention they do.
The loft party wall
Building Regulations guidance requires the wall separating dwellings to continue up through the roof space to the underside of the roof covering, so a fire in one loft does not run straight into the neighbour's. In older terraced and semi detached housing that wall frequently stops at ceiling level or has been breached for pipework, an aerial cable or a shared water tank. It is invisible from inside the house and common enough to be worth checking.
How fire walls get breached
New services run through after completion. A loft conversion or a bathroom refit. Recessed lights cutting the ceiling below. Aerial and satellite cabling. A shared cold water tank. A previous owner making a storage hatch. Each is small, each is invisible from the habitable rooms, and each reduces a fire resisting wall to a decorative one.
Checking and putting it right
Looking in the loft with a torch tells you most of what you need to know: does the wall reach the roof, is it complete, are there holes. Making good is usually blockwork or a fire rated board system taken up to the underside of the roof, with the junction detailed properly. It is ordinary building work, and in a terrace it is the single most valuable fire safety improvement available to most households.
Questions people ask about fire wall
Should the wall between two houses go up into the loft?
Yes. Building Regulations guidance requires the separating wall to continue to the underside of the roof covering. In older housing it frequently stops at ceiling level, which is invisible from inside the house.
What is the main objective of compartmentation?
To confine a fire to the area where it started for long enough that people can escape and the fire service can act, by dividing the building with fire resisting walls and floors.
How do I check my loft party wall?
Look with a torch: does the wall reach the roof, is it complete, and are there holes for cables, pipes or a shared tank. Any of those is worth putting right.
What do the fire wall in loft regulations UK wide expect?
In a terrace or a semi the separating wall is meant to continue up through the roof void to the underside of the tiles, so a fire in one roof space does not run along the terrace. The guidance for new work asks for that continuity and for it to be sealed where members pass through; on older properties it is one of the commonest defects found when somebody finally goes into the loft, because the wall stops at ceiling level or has been broken through for a cable, a flue or a loft conversion. It is also a question a lender's surveyor raises in a converted house, which is when most people discover it.