Structural Alterations: Removing Walls and Installing RSJs

Is the wall load bearing?

Never assume from thickness alone. A useful first test is direction: internal walls running perpendicular to the floor joists above are far more likely to be carrying them. Tap it too, as a solid masonry wall sounds dull and a stud partition sounds hollow, but be aware that stud walls can still be structural.

Look in the loft and at the joist direction, check whether the wall continues on the floor above and down to a foundation, and check whether anything sits directly over it. If there is any doubt at all, this is a job for a structural engineer, not a judgement made with a hammer.

Runs perpendicular to the joists above: likely load bearing · Continues through more than one storey: likely load bearing · Sits directly under a wall, stack or roof member above: likely load bearing · Sounds hollow and stops at ceiling level with nothing above: likely a partition · Spine wall running the length of a Victorian terrace: almost always load bearing

What the structural engineer actually does

An engineer calculates the loads carried by the wall, including the floors, roof and any walls above, then specifies a beam capable of carrying them with acceptable deflection. Deflection matters as much as strength, because a beam that is strong but flexible cracks the plaster above it.

The design also specifies the bearings: how far the beam sits onto the masonry at each end, and the padstones or spreader plates that distribute the load into the wall below. Bearings are where amateur jobs fail, because a beam concentrating tonnes onto ordinary brickwork will punch straight into it.

Expect calculations, a sketch and a schedule for around £500 to £1,200 on a typical domestic opening, and to submit them to building control under a full plans application.

How the work is sequenced on site

The order is not negotiable and it is what you are paying for. Services are traced and isolated first, because a chased-in cable or a hidden pipe discovered mid-demolition is a bad day.

Trace and divert electrics, plumbing and any gas within the wall · Install acrow props with proper needles and sole plates on both sides · Cut the opening in stages, never in one go · Bed the padstones and allow the mortar to gain strength · Lift and set the beam, pack the bearings solidly · Pin the masonry above tightly with slate or dry-pack mortar · Fire-protect the steel, usually with two layers of plasterboard · Remove props only after the structure has taken the load · Call the building control inspection before anything is boarded over

Indicative costs for internal structural work

Figures below are typical South East ranges for 2026 and cover the structural work plus making good, but not flooring, kitchens, electrics beyond diversions or decoration.

Indicative structural alteration costs, South East England (2026). Work | Indicative range | Typical duration. Remove a non-load-bearing stud partition — £600 – £1,200 — 1 – 2 days; Single opening with one steel beam — £2,500 – £5,000 — 4 – 7 days; Full wall removal, two rooms into one — £4,000 – £8,000 — 1 – 2 weeks; Wide opening requiring goalpost frame with posts — £6,000 – £12,000 — 2 – 3 weeks; Chimney breast removal with gallows or beam support — £2,000 – £4,500 — 1 week; Structural engineer's calculations — £500 – £1,200 — 1 – 2 weeks; Building control full plans — £600 – £1,000 — Runs alongside

The consequences people forget

Removing a wall changes more than the plan. Heating needs rebalancing because one large space behaves differently from two small ones, and radiator positions rarely survive intact. Lighting has to be redesigned, since two ceiling roses in a knocked-through room look exactly like two rooms that used to be there.

Acoustics change noticeably, floor finishes have to run through or be deliberately divided, and the ceiling almost always needs a full skim rather than a patch, because the junction line will otherwise track through the paint within a year.

Party walls, terraces and semis

Cutting into a shared wall to bear a beam is notifiable work under section 2 of the Party Wall etc. Act 1996, with a two month notice period. This catches out a great many terrace and semi-detached projects, because the beam has to bear somewhere and one end is frequently the party wall.

Serve the notice as soon as the engineer confirms the bearing detail. It runs in parallel with building control and does not have to delay anything, provided it starts early.

Paperwork to keep

Keep the engineer's calculations, the beam and padstone schedule, the building control completion certificate and any party wall award together. A buyer's surveyor will ask, and open-plan work without calculations is one of the more common reasons for a retention or price reduction at sale.

Frequently asked questions

Do I need planning permission to remove an internal wall?

Not usually, since it is internal work, unless the property is listed, in which case listed building consent is required. Building regulations approval is always needed for a structural alteration.

How long does the room take to be usable again?

The structural work is typically four to seven days for a single opening. Plastering, drying, decoration and flooring add another one to two weeks before the space feels finished.

Can I remove a chimney breast on one floor only?

Yes, but the remaining stack above must be supported, usually with gallows brackets fixed into sound masonry or a beam. It is notifiable structural work and needs building control approval.

What is the difference between an RSJ and a UB?

RSJ is the older term for a rolled steel joist. Most modern beams are universal beams, which have wider flanges and better load characteristics. Builders use the terms interchangeably; the engineer's schedule specifies the exact section.