Structural Alterations in London Homes: Opening Walls, Steels, and Load-Bearing Walls

Not all walls are structural. Understanding which walls are load-bearing and which are not is the first step in any internal alteration project.

**Load-bearing walls** carry the weight of the structure above them — typically floors, roofs, or upper walls — down to the foundations. They are an integral part of the building's structural system. Removing or opening a load-bearing wall without proper structural support will cause the structure above to settle, crack, or fail.

**Non-load-bearing walls** (also called partition walls) simply divide space. They carry no structural load from above. Removing a partition wall is relatively straightforward and does not require structural engineering.

**How to identify a load-bearing wall**: - Walls running at 90 degrees to the floor joists are typically load-bearing (they carry the joists) - Walls that continue through multiple floors at the same position are typically load-bearing - In Victorian terraced houses, the spine wall running front-to-back through the centre of the house is almost always load-bearing - External walls are always structural - Chimney breast walls are structural (and chimney breast removal is a separate and complex structural operation)

Always have a structural engineer confirm which walls are load-bearing before any structural alteration work starts. Do not rely on visual assessment alone.

When a load-bearing wall is removed or an opening is created, a steel beam (commonly called an RSJ — Rolled Steel Joist, or an I-beam) spans the opening and carries the load that the removed wall was previously transferring.

**How steel beams work**: The beam spans between two support points — the remaining wall sections, or columns — and transfers the load to the foundations at each end. The beam must be sized to carry the specific loads at each point: the floor loads above, the wall loads above, and in some cases, the roof loads.

**Padstones**: Where a steel beam sits on masonry, a concrete or engineering brick padstone is required to spread the point load over an adequate bearing area. Padstones are sized by the structural engineer.

**Beam sizing**: The structural engineer calculates the required beam size (depth, flange width, and section classification) based on the span, the loads, and the required deflection limits. Common RSJ sections for domestic openings range from 127x76x13 UB (for small openings under 2m carrying light loads) to 305x165x54 UB or larger for wide openings or heavy roof loads.

**Steel supply**: Steels are typically fabricated or sourced from a local steel stockholder. They are heavy — a standard 203x102x23 UB at 3m is approximately 69kg — and require lifting equipment or multiple operatives to place safely.

Before a load-bearing wall can be removed or opened, the structure above it must be temporarily supported. This is done with a system of temporary works: needles and props (also called Acrow props or telescopic steel props).

**The temporary works sequence**: 1. Prop up floor or ceiling above the intended opening from both sides 2. Form a small pilot hole through the wall to thread the needle beam through 3. Place needle beams (horizontal temporary steels) through the wall at intervals 4. Support the needle beams on props on both sides of the wall 5. Remove the wall material within the opening 6. Install permanent beam in position 7. Remove temporary works progressively once beam is bearing

Temporary works must be adequately designed and not improvised. For wide openings or high loads, a temporary works engineer may need to design the propping scheme. The structural engineer's drawing for the permanent works typically includes notes on temporary support requirements.

Before starting any structural alteration, have the wall opened from one side to check for any services (pipes, cables) concealed within. Finding a waste pipe in the middle of a planned opening after the wall is half demolished is a common and expensive surprise.

Structural alterations require Building Regulations approval — this is not optional. The process:

1. **Full Plans application**: Submit structural drawings and calculations to Building Control before work starts. Approval is issued, subject to site inspection at key stages. 2. **Building Notice**: An alternative route for simpler works — notify Building Control, and an inspector visits during construction. Less suitable for complex structural works.

Key Building Regulations elements for structural alterations: - **Part A (Structure)**: The engineer's design must demonstrate structural adequacy of the beam, supports, and connections - **Part B (Fire Safety)**: Where walls are removed, fire compartmentation may be compromised. In a standard terraced house, removing the ground floor spine wall between kitchen and dining room does not typically raise Part B issues, but changes to structural walls that form a fire separation between units do - **Part C (Damp)**: Where the wall to be removed sits on the damp-proof course line, details must be designed to maintain DPC continuity - **Part L (Energy)**: Where a structural alteration exposes insulation gaps, they should be addressed during the works

A Building Regulations completion certificate is issued after successful final inspection. This document is required on sale.

Chimney breast removal is a specialised structural alteration that deserves separate consideration. In a Victorian terraced house, a chimney breast projects into the room from each external or party wall. Removing a chimney breast — to reclaim floor space or to open up a wall — is one of the most frequently requested but frequently mishandled structural alterations.

The complication is that a chimney breast in a lower room typically supports the chimney breast in the room above and the chimney stack on the roof. Simply removing the ground-floor chimney breast without supporting the breast above will cause the upper breast to collapse or crack.

**Correct approach**: A structural engineer designs a steel 'gallows bracket' or similar support that transfers the load of the upper chimney breast and stack to the adjacent walls, allowing the lower breast to be removed safely. The engineer's drawings must accompany a Building Regulations application.

Cost of chimney breast removal: typically £3,500–£8,000 including structural engineer, steel supply and installation, Building Control, re-plastering, and making good the floors.

Typical costs for common structural alterations in London (2025):

- **Structural engineer fee (drawings + calculations)**: £600–£1,800 depending on complexity - **Building Regulations application (Full Plans)**: £500–£1,200 - **Removing a non-load-bearing partition wall (1 room)**: £800–£2,000 including making good - **Creating a structural opening in a load-bearing wall (up to 3m wide)**: £2,500–£5,500 including steel, padstones, temporary works, and making good - **Full wall removal — ground floor spine wall (full kitchen-to-dining opening)**: £4,000–£8,000 - **Chimney breast removal (single storey with gallows bracket)**: £3,500–£8,000

Structural alterations are typically part of a wider refurbishment or extension project rather than a standalone operation. The structural alteration costs above form one component of the overall project cost.