Question 1

How much does it cost to remove a load-bearing wall in London?

Accepted Answer

Removing a load-bearing wall and installing a steel beam (RSJ) typically costs £3,500-£8,000 in London. The cost depends on the span (longer = bigger steel = more expensive), the number of temporary supports (Acrow props) needed, the floor type above (timber joists vs concrete), and whether a party wall is involved. A structural engineer's calculation is required and typically costs £400-£800. Building Control notification is mandatory. Wider openings (over 3.5m) or openings near party walls cost more due to padstone and bearing requirements.

Question 2

How do I know if a wall is load-bearing?

Accepted Answer

Indicators that a wall is load-bearing include: it runs perpendicular to the floor joists above, it sits directly above the foundation line, it is a party wall shared with a neighbour, it is an external wall, or it supports a chimney breast above. However, you should never rely on visual inspection alone. A structural engineer must confirm whether a wall is load-bearing and design the replacement support (steel beam, padstones and temporary works). The cost of getting this wrong is catastrophic - partial or full structural collapse. RCB always commissions a structural engineer before any wall is touched.

Question 3

What is an RSJ and why are they used in residential work?

Accepted Answer

RSJ stands for Rolled Steel Joist - it is a steel beam with an I-shaped cross-section used to support the load above when a wall is removed. In residential work, RSJs (now technically called UB - Universal Beams) are used to: create open-plan living spaces by removing internal walls, support upper floors when ground-floor walls are opened up, carry roof loads in loft conversions, and span openings for new windows or bi-fold doors. The beam size is calculated by a structural engineer based on the loads, span and bearing conditions. Common residential sizes range from 152x89mm (small openings) to 305x165mm (large spans).

Question 4

Do I need Building Control for structural work?

Accepted Answer

Yes - all structural alterations require a Building Control application. This includes removing load-bearing walls, installing steel beams, creating new openings in walls, underpinning, changes to floor structure, chimney breast removal, and any work affecting structural stability. The structural engineer's calculations must be submitted with the application. Building Control inspects at key stages: temporary works, steel installation, bearing connections, and completion. Fees range from £400-£1,200 depending on the council and project value. Work must not start until the application is registered.

Question 5

What is underpinning and when is it needed?

Accepted Answer

Underpinning strengthens or deepens existing foundations. It is needed when: (1) existing foundations are too shallow for a new extension (common on pre-1960s properties built with shallow strip foundations); (2) subsidence has damaged the structure and the foundations need stabilising; (3) you are excavating a basement or lowering a floor level below the existing foundation depth; (4) the ground conditions have changed (e.g. nearby tree roots causing clay shrinkage). Traditional mass concrete underpinning costs £1,500-£3,000 per linear metre. Mini-piled underpinning costs £2,500-£5,000 per pile and is used for deeper or more complex ground conditions.

Question 6

Can I remove a chimney breast?

Accepted Answer

Yes, but it requires structural support and Building Control approval. If you remove a chimney breast on the ground floor only, the first-floor breast and chimney stack above must be supported with steel beams or a gallows bracket. If you remove it on all floors, the chimney stack on the roof must also be removed. If the chimney is on a party wall, a Party Wall Notice must be served. Costs range from £1,500-£4,000 for a single-floor removal and £3,000-£7,000 for a full removal including stack. Asbestos surveys are recommended for pre-1980s properties as flue liners may contain asbestos.

Question 7

What temporary support is needed during structural work?

Accepted Answer

When removing a load-bearing wall, the load must be temporarily supported while the permanent steel beam is installed. This typically involves Acrow props (adjustable steel props) positioned under strongboy brackets or needles that transfer the load through the wall before it is removed. The structural engineer specifies the temporary works scheme, including prop positions, needle sizes and sole plate requirements. Temporary works must be in place before any demolition begins and remain until the permanent steel is fully loaded and padstones are set. The propping period is typically 3-5 days per opening.

Question 8

How long does structural work take?

Accepted Answer

A single wall removal with steel beam installation takes 3-5 days from propping to completion (excluding making good). Multiple openings on the same floor take 5-10 days. Adding the subsequent plastering, decoration and floor repairs extends the total to 2-4 weeks per room affected. Underpinning a typical terraced house rear wall (6-8m) takes 3-4 weeks because it must be done in alternating 1m bays, allowing each section to cure before the adjacent bay is excavated. Allow additional time for structural engineer site visits and Building Control inspections.

Question 9

What is a structural survey and when do I need one?

Accepted Answer

A structural survey (RICS Level 3 Building Survey) is a detailed inspection of a property's structural condition. You need one when: buying a property built before 1950, purchasing a property with visible cracking or settlement, planning major structural alterations, or investigating suspected subsidence. The surveyor examines foundations, walls, floors, roof structure and drainage. Costs range from £600-£1,500 depending on property size. For specific structural alteration work, a structural engineer (chartered, CEng MIStructE) designs the solution and provides calculations - this is different from and additional to a building surveyor.

Question 10

What are padstones and why are they important?

Accepted Answer

Padstones are dense concrete or engineering brick blocks placed at each end of a steel beam where it bears on the wall. They spread the concentrated point load from the beam across a wider area of masonry, preventing localised crushing of the brickwork. The structural engineer specifies the padstone size based on the beam reaction (load) and the crushing strength of the existing masonry. Common sizes are 215x215x140mm for light beams and 440x215x215mm for heavier loads. Using the wrong padstone (or none) can cause the beam to crush through the wall over time, leading to cracking and settlement.

Structural Alterations FAQs

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