Opening Up a Wall: RSJs, Structural Openings, and Temporary Support
Removing a wall to open up a ground floor, merge a kitchen and dining room, or create a flowing living space is one of the most transformative things you can do in a home. It is also one of the most technically involved — not because it is impossibly complex, but because the sequence and the structural decisions genuinely matter. Done properly, a wall removal is safe, clean, and long-lasting. Done without proper preparation, it can cause movement, cracking, or worse.
Here is what you need to understand before any work starts.
Is the Wall Structural?
Not every wall is structural, and identifying the difference is the essential first step. A structural (load-bearing) wall carries loads from the floor or roof above and transfers them down to the foundations. A partition wall simply divides space and carries nothing but its own weight.
A few indicators can help, though a structural engineer should always confirm:
Direction relative to the joists. Floor joists typically span the shortest distance across a room. A wall that runs perpendicular to the joists — at right angles to the direction they span — is likely to be carrying their load and is therefore structural. A wall running parallel to the joists is more likely to be a partition.
Position on multiple floors. If a wall sits directly above another wall on the floor below, and another wall runs below it at ground floor level, there is a strong likelihood of a load path running down through the structure.
Ground-floor position. Ground-floor walls running parallel to the front and rear of the property and sitting centrally in the plan are frequent candidates for load-bearing walls in typical Victorian and Edwardian terraced houses.
Visual cues can help, but they are not definitive. Only a structural engineer's inspection — ideally including a look at the roof and floor construction — gives you a reliable answer.
What the Structural Engineer Provides
Once a structural engineer (SE) confirms the wall is load-bearing, their role is to specify what replaces it. The most common solution is a steel beam — in everyday speech, an RSJ (Rolled Steel Joist), though the technically precise modern term is Universal Beam (UB). In practice, both terms refer to the same family of structural steel sections.
The SE's calculations determine the beam size required to safely span the opening, based on the loads it must carry — which include the weight of floors, walls, and roof above. The calculation also specifies the padstones at each end of the beam: load-spreading bearing elements (typically formed in engineering brick or concrete) that distribute the concentrated point load from the beam into the adjacent masonry.
Without SE calculations, there is no reliable way to determine whether a beam is adequately sized. Undersized beams deflect, causing cracking at the ends of the opening, distortion in floors above, and potentially worse.
Temporary Support: The Sequence Before the Steel Goes In
To install a permanent beam, the loads it will eventually carry must first be transferred temporarily to another load path. This is achieved using adjustable steel props (acroprops) and temporary beams — a process sometimes referred to as needling when the temporary structure passes through the wall to pick up loads on both faces simultaneously.
The temporary support must be properly designed and positioned before any masonry is disturbed. It holds the loads while the permanent beam is installed, padstones are set, and the new structural condition is made permanent. Only then can the temporary props be removed.
This sequence is not optional. It is the difference between a controlled structural operation and an uncontrolled one.
Building Regulations and Inspections
A structural opening is a notifiable alteration under the Building Regulations 2010. Whether you use Full Plans or Building Notice, Building Control must be informed, the structural engineer's calculations must be available for inspection, and a Building Control officer will inspect at the relevant stages — including before the opening is formed and after the beam is installed.
A Completion Certificate should be issued at the end of the project. For the reasons discussed in our post on Building Control, this matters for any future sale or remortgage.
Chimney Breast Removals
Removing a chimney breast requires particular care. The chimney structure above the removed section must be adequately supported — usually by a padstone bearing off the party wall or flank wall, with the remaining stack above corbelled or carried on the beam. Where the chimney is shared with a neighbouring property (common in Victorian terraces), the structural and legal implications are more involved.
This brings in the Party Wall Act. If the wall being altered is a party wall — shared with an adjoining owner — works under section 2 of the Party Wall etc. Act 1996 are likely to apply. A party wall notice must be served on the adjoining owner(s) before work starts. If they consent, work can proceed. If they dissent or do not respond, the Act's surveyor mechanism engages. Failing to serve notice does not make the works unlawful in planning terms, but it does create civil liability to the adjoining owner.
Common Mistakes to Avoid
Assuming a wall is non-structural because it looks like a partition is a mistake that shows up in cracking, sticking doors, and structural movement after the event. Starting without SE calculations risks a beam that is either underspecified or unnecessarily large — both costly in different ways. Not engaging Building Control means no Completion Certificate and a more complicated property sale.
At RCB Design & Build, we coordinate the structural engineer, Building Control, and temporary works as a managed part of our delivery. You do not need to navigate these relationships separately. If you are planning a wall removal, kitchen knock-through, or chimney breast removal in London, speak to us first at contact@rcbgroup.co.uk or +44 7359 872594.