Knock-Through Costs UK — What to Charge to Remove a Wall in 2026

The First Question: Is the Wall Load-Bearing?

Everything about the price hinges on this. A non-load-bearing wall carries nothing but its own weight — you can take it out without supporting anything above it. A load-bearing wall holds up the floor joists, ceiling, roof or another wall above, and removing it without a properly sized beam will bring the structure down. Never price a knock-through until you know which you are dealing with.

Quick checks a builder uses on site:

• Direction of the joists: if the floor or ceiling joists run perpendicular to the wall (bearing onto it), it is almost certainly load-bearing. Joists running parallel suggest non-load-bearing — but confirm it.
• Thickness and construction: a solid masonry wall (brick or block) is far more likely to be structural than a thin stud partition you can knock and hear hollow.
• Position in the building: internal walls that stack vertically through the storeys, or that sit central in the footprint, are commonly load-bearing.
• What is above: a wall directly under another wall, a chimney breast, or a load-bearing spine usually carries weight.

These checks tell you what you are likely facing, but they are not a substitute for a structural engineer. On any wall that might be load-bearing, the engineer's calculations are what determine the beam size — and what building control will sign off. Do not guess. Getting this wrong is the one mistake in this trade that can be catastrophic and uninsurable.

Scenario 1: Removing a Non-Load-Bearing Wall

This is the cheap, quick job. A stud partition (timber frame with plasterboard) or a single-skin block wall that carries no structural load can be taken down without any beam, because nothing above it needs supporting. The work is essentially demolition plus making good.

Even on a simple job there is more than just knocking the wall down. You need to check for and reroute any services hidden in the wall — electrical cables, sockets, switches, light fittings, central heating pipes or a radiator fixed to the wall. There is dust protection to set up, debris to clear and skip away, and then the floor, ceiling and walls to make good where the partition met them.

• Typical job (stud or single-skin, minimal services): £500–£1,500
• Labour: usually 1–2 days for two people including making good
• Skip hire: £200–£350 depending on size and region

Most non-load-bearing knock-throughs do not need building control approval for the structural element, but notifiable electrical work (Part P) and any gas work still need to be carried out by a competent registered person. Price the making good carefully — it is where the time and the margin go.

Scenario 2: Removing a Load-Bearing Wall (Steel Beam / RSJ)

This is the standard knock-through job — and where the real money and the real risk sit. When the wall carries load, you cannot simply remove it. You install a steel beam (an RSJ — rolled steel joist — or a UB universal beam) across the opening to carry everything the wall was holding up, then take the wall out from beneath it.

The sequence on site is what separates a competent builder from a dangerous one:

• Temporary support first: Acrow props and strongboys, or props and needles passed through the wall, take the load before you cut anything. The structure is supported at all times.
• Bearings and padstones: the beam has to land on something that can take the point load. That usually means concrete padstones (or proprietary spreader plates) built into the wall at each end, sized by the engineer.
• Lift and seat the beam: steels are heavy — a domestic beam can weigh 60–150kg or more and often needs two or three people or a lifting aid to position.
• Transfer the load: pack and pin the beam tight under the structure above, then remove the temporary props once it is bearing.
• Fire protection: exposed steel needs encasing — boxed in with fire-rated plasterboard or intumescent treatment to meet building regs.

You will also need a structural engineer's calculations to size the beam and the padstones, and building control approval and inspection (see below). The beam itself is a real cost: steel prices fluctuate, and a typical domestic beam supplied and cut runs from a few hundred pounds for a short span to well over £1,000 for a long or heavy section.

• Typical load-bearing knock-through with one steel beam: £2,000–£5,000
• Labour: usually 3–7 days including propping, beam install, making good and decoration
• Steel beam supplied: £250–£1,200+ depending on span and section

Scenario 3: Large Open-Plan Knock-Through

At the top end you have the big open-plan jobs — knocking through and removing a long stretch of wall, taking out a chimney breast at the same time, or spanning a wide opening that needs a deeper or doubled-up beam. These often involve two or more storeys of load above, multiple bearings, and significant making good across a large floor and ceiling area.

Costs climb because the beam is bigger and heavier (and may need a structural opening to get it into the property), there is more temporary propping, more services to relocate, and far more making good — levelling and laying a continuous floor across what were two rooms, running a continuous ceiling, moving radiators and rewiring sockets to suit the new layout.

• Large open-plan knock-through: £5,000–£10,000+
• Wide-span or multi-storey-load beams may need craneage or extra labour to lift
• Chimney breast removal as part of the job adds gallows brackets or a support beam, plus the cost of working at height in the loft

On jobs of this size, price the making good and the services as their own line items. A continuous floor finish, a re-skimmed ceiling and a fully reworked electrical and heating layout can easily account for half the total — and it is the half builders most often forget to quote.

Structural Engineer and Building Control

For any load-bearing knock-through, two professional costs are non-negotiable and must be in your quote (or clearly flagged as the client's responsibility).

Structural Engineer's Calculations

A structural engineer surveys the wall, works out the load it carries and produces calculations specifying the beam size, the bearing length and the padstone sizing. Building control will not sign off without them, and you should not order steel without them.

• Engineer's calculations for a single beam: £300–£600
• More complex jobs (multiple beams, chimney removal, wide spans): £600–£1,200+

Building Regulations / Building Control

Removing or altering a load-bearing wall is notifiable structural work under the Building Regulations. You submit a Building Notice or full plans to the local authority building control (or use an approved inspector), and an inspector visits to check the beam, the bearings and the temporary support before the work is closed up and again on completion. The end result is a completion certificate the homeowner will need when they sell.

• Building control fees for a typical knock-through: £300–£600
• Inspections: usually a beam/structure visit plus a completion visit

Make clear in writing who is arranging and paying for the engineer and building control. If you build it into your headline price, itemise it so the customer understands these are third-party costs and not your margin.

Making Good — Where the Time Goes

The structural part of a knock-through can be over in a day or two. The making good is what fills the rest of the week and where margin is won or lost. Quote each element rather than lumping it into a round figure.

• Plastering: re-skim the reveals, box in the beam, patch where the wall met the ceiling and walls, and often skim larger areas to get a uniform finish across the joined room.
• Flooring: the two rooms rarely line up. Expect to level the floor, fill the channel where the wall sat, and lay a continuous finish so there is no ridge across the opening.
• Skirting and architrave: run new skirting around the opened space to match or replace throughout.
• Electrics: sockets, switches and lights on the removed wall have to be moved or removed; the new larger room often needs the layout reworked. Notifiable work needs a Part P certificate.
• Heating: a radiator fixed to the lost wall must be relocated, which means a plumber draining down, moving pipework and rehanging it elsewhere.
• Redecoration: the joined room almost always needs decorating throughout so the two halves match.

Services, Dust and Protection

Before any wall comes down, find out what runs through it. Cables and pipes buried in a wall you are about to demolish need isolating and rerouting — cutting a live cable or a heating pipe turns a clean job into an emergency. Use a detector, check both faces, and trace where circuits run.

Demolition is filthy. Knocking out masonry generates enormous quantities of fine dust that travels through the whole house. Proper dust protection — sealed doorways with zip screens, floor coverings, dust sheets over furniture and a dust extractor or air scrubber — is part of a professional job and part of your cost. Cutting corners here is how you lose a customer even on a technically perfect knock-through.

What Affects the Price

Two load-bearing knock-throughs in similar houses can quote very differently. The main price drivers:

• Beam size and span: a wider opening needs a deeper, heavier — and more expensive — beam, and more effort to lift and seat it.
• Steel cost: steel prices move; price the actual section from a current supplier quote rather than from memory.
• Storeys of load above: a wall carrying just a ceiling is far lighter than one carrying floors and roof above — bigger load means a bigger beam and bigger bearings.
• Access: getting a long, heavy steel into a terraced house or up a narrow hallway can need extra labour or even a structural opening; restricted access adds time.
• Chimney breast involved: removing a chimney breast alongside the knock-through adds support work, height and complexity.
• Condition and construction: old, soft or rubble-filled masonry, lintels in poor condition, or unexpected structure can all add cost once the wall is opened up.
• Extent of making good: the bigger the joined space, the more flooring, plastering, heating and electrical rework — usually the largest variable in the whole quote.

Quoting Tips — What to Check Before You Price

Knock-through quotes go wrong when the builder prices off the wall alone and forgets everything around it. Before you commit a price:

• Confirm load-bearing status and get the structural engineer involved before quoting a firm price on a structural wall.
• Find the services in and around the wall — cables, sockets, pipes, radiators — and price relocating each one.
• Measure both rooms for floor levels and finishes so you can price levelling and a continuous floor.
• Check what is above — another storey, a chimney, a roof — to anticipate beam size before the engineer confirms it.
• Itemise third-party costs — engineer, building control, skip — separately so the customer sees they are not margin.
• Allow for dust protection and clearance as real lines, not an afterthought.

A clear, itemised quote that separates the structural work, the steel and professional fees, and the making good wins jobs against rivals who just send a single number — and it protects you when the customer questions the price later.

Quick Reference: Knock-Through Costs UK 2026