Removing a Load-Bearing Wall for an Open-Plan Kitchen

What the wall carries. It is a load-bearing spine wall in the middle of the house. It takes half the span of the first-floor joists from each side, and it also takes the first-floor stud partition running along the same line. Removing it means transferring both loads sideways to the external walls, which is a structural alteration to the building, not a decorative one. The Building Regulations require the work to be designed and certified, and Building Control will require a commencement notice and a design certificate from a competent person; the absence of a party wall is irrelevant to that.

Two further points the builder missed: the wall may be providing lateral restraint to the external walls (it is parallel to the front and rear walls, so it restrains them out of plane), and the removal may affect the buttressing of the gable or party wall. Both must be checked and, if necessary, restraint straps specified.

Order-of-magnitude estimate. Floor loading: dead about 1.5 kN/m² (joists, deck, finishes, ceiling, services), domestic live 1.5 kN/m², giving roughly 3.0 kN/m² characteristic and about 4.4 kN/m² with typical partial factors.

• Each side contributes half the joist span: 2.0 m × 4.4 kN/m² = 8.8 kN/m.
• Two sides: 17.6 kN/m.
• Partition above: about 0.5 kN/m² over 2.7 m height ≈ 1.4 kN/m × 1.35 ≈ 1.8 kN/m.
• Total design load ≈ 19 kN/m over a 4.2 m span, giving a moment of about wL²/8 ≈ 42 kNm and an end reaction of about 40 kN at each bearing.

This is enough to show why 100 mm bearings with ply packing are not acceptable: 40 kN on a 220 × 100 mm bearing is roughly 1.8 N/mm², well above what a typical 7 N/mm² blockwork can be relied on to take locally without a padstone. A precast concrete or dense block padstone of at least 300 mm length should spread the reaction.

Strength is not the governing issue - stiffness is. A 178 × 102 × 19 UB in S275 has a plastic modulus of about 171 cm³, which is more than adequate for a 42 kNm moment. It would not fail. It would deflect, and deflection limits exist to protect the plasterboard and the finishes above and below.

Check the deflection. For a simply supported beam, δ = 5wL⁴/(384EI). With an unfactored serviceability load of about 13 kN/m, L = 4,200 mm, E = 210,000 N/mm² and I ≈ 1,366 cm⁴ for a 178 × 102 × 19:

• δ ≈ 18 mm.
• Allowable is span/360 ≈ 11.7 mm where brittle finishes and plasterboard are involved (span/250 ≈ 16.8 mm would apply only to a more tolerant situation).

The beam fails the deflection check at both limits. Moving to a 203 × 133 × 30 UB (I ≈ 2,896 cm⁴) roughly halves the deflection to about 9 mm, which passes span/360 comfortably - the increase in I, not in strength, is what fixes the problem.

What that means for the flush ceiling. The beam must be deeper to be stiff enough. A 203 UB is about 207 mm deep against 200 mm joists, so a truly flush soffit is not achievable without either notching/dropping the ceiling locally by 10–15 mm (a shadow gap or a small bulkhead), or hanging the joists from the beam and accepting a marginally lower ceiling, or using a deeper section concealed within a slightly dropped ceiling zone.

Conclusion. This is exactly why the design must be done by an engineer before the builder orders steel: the depth of the beam is set by deflection, and the depth is set by the client's flush-ceiling requirement. The client must be told now that a perfectly flush soffit is likely to cost either a small downstand or a lower ceiling, and choose.

Before work starts

• Engineer's design and drawings for the beam, bearings, padstones and any restraint straps; the beam specification must state the section, grade, and bearing details, not just a size.
• Building Control commencement notice and the relevant design and construction certificates in place.
• Check for services in the wall (cables, pipes) and confirm the escape route from the first floor is not affected - an open-plan ground floor can change fire escape and smoke travel, and may require mains-operated smoke alarms linked between floors.
• Agree the flush-ceiling compromise with the client in writing.

During the work

• Erect temporary props and needles on both sides of the wall, designed for the load, before any block is removed; prop positions should not be removed until the beam is bedded and the mortar or padstone has gained strength.
• Cut a neat chase for the beam bearings, form the padstones, and bed the beam level and to the correct line and level with a non-shrink bedding.
• Provide lateral restraint to the beam, and straps to the external walls where the engineer requires them.
• Infill the gap between the beam and the joists and pack solid so the joists bear properly and do not rotate.

After the work

• Inspect bearings and packing before the ceiling is closed up; take photographs for the certifier.
• Remove props only when the engineer permits.
• Fire-line the steel if it is exposed (typically an intumescent coating or a encased casing) where it forms part of a compartment or protected escape route.
• Obtain the engineer's certificate of compliance and completion documentation for the Building Control file.