Open Plan Knock Through: Costs, Structure and Rules
An open plan knock through means taking out some or all of the wall between two rooms, usually the kitchen and dining room, so they work as one space. If the wall is load bearing, the job needs a structural engineer’s design, a steel beam or similar support, temporary propping and Building Regulations sign-off. If it is not, the work is simpler, but you still need to confirm that before anyone picks up a sledgehammer.
This guide takes you through the decisions in the order you will face them: finding out what the wall does, choosing how wide to open it, understanding the paperwork, budgeting realistically and briefing a builder so the quote you receive can be compared fairly.
TL;DR
Removing a load bearing wall is structural work. You need an engineer’s calculations, a properly supported beam and Building Regulations approval, not a guess based on wall thickness.
Planning permission is not normally needed for internal changes to a house, but Building Regulations usually apply. Flats, leasehold homes, listed buildings and conservation areas add extra checks.
Published cost guides range from roughly £975 for a single doorway opening to several thousand pounds for a wide opening, before electrics, plastering, flooring and decoration.
Ask every builder to price steelwork, making good and service alterations as separate lines, so a low headline figure does not hide extras.
Table of Contents
First, find out what the wall actually does
Every wall in your home is either load bearing or a partition. A load bearing wall carries weight from floors, the roof or other walls down to the foundations. Planning Portal describes load bearing walls in exactly those terms, and it is the starting point for every knock through.
Homeowners often try to work this out from clues: a thick wall, joists running a particular way, a hollow sound when tapped. None of these is reliable on its own. Official guidance is clear that the decision should combine a structural assessment with checks on fire safety, ventilation, drainage and electrical services.
Some sensible first observations, which tell you what to ask rather than what to conclude:
Is there a wall directly above or below? A wall that stacks over another wall on the floor above or below is more likely to be carrying something.
Which way do the floor joists run? Joists that rest on the wall are a sign it is structural, though the reverse is not proof of safety.
Is it an original wall or a later addition? Older houses, particularly Victorian and Edwardian terraces common across north and east London, often have walls that support chimney breasts or upper floors.
Has the house been altered before? Earlier extensions or loft conversions can change where the loads go.
The only dependable answer comes from a structural engineer who inspects the property and, where needed, opens up a small area to see what bears on what.
Choosing the type of opening
The design question comes before the engineering one: how much of the wall do you want to lose? It shapes the cost, the disruption and how the finished room feels.
Full-width opening
A fully open kitchen-diner gives the clearest sightlines and the most light. It also asks the most of the structure. Structural engineers point out that longer spans mean deeper beams, higher loads at the ends and more concern about movement, and that open plan finishes make any cracking easier to see. Wide openings may also need posts, padstones or a goalpost frame where the end masonry cannot carry the load safely.
Partial opening or wide doorway
Keeping a short return of wall at one or both ends can reduce the span, hide the beam ends and leave you a place for tall cabinets, a radiator or a sofa back. Many families find this a more comfortable compromise, because it also lets you define the kitchen and dining zones.
Opening to an extension
If you are adding a rear or side return extension, the old external wall often comes out as part of the build. That is normally designed together with the extension’s structure rather than as a separate knock through. It is worth planning both at once so that beams, foundations and finishes line up. Our page on home extensions sets out the options we build.
Headroom and the beam
A beam can sit below the ceiling as a visible downstand, or the design may place it within the floor depth above so the ceiling stays flat. The second approach usually costs more in labour and finishing, and is not always possible. Ask the engineer which options are realistic for your house before you fall in love with a particular look.
What the structural design involves
The size of the beam, and how it is supported, depends on the span and the loads above. According to Homebuilding’s guidance, a beam or lintel normally needs bearing beyond each side of the opening and extra support beneath its ends. The exact dimensions must come from calculations for your project, not from a rule of thumb or from a neighbour’s house.
The engineer will typically:
Visit and record the wall, floors above, roof structure and any previous alterations.
Calculate the loads and choose the beam, lintel or frame, with bearing and connection details.
Produce drawings and calculations that your builder works to and that Building Control can approve.
The real danger is not the visible removal of the wall. Building control practitioners stress that the risk lies in losing the load path during temporary works, or in hiding inadequate bearings and connections. A competent contractor should be able to explain the propping and inspection sequence before demolition begins. If a builder cannot, or says you do not need calculations, treat that as a warning.
The safe order of work
Building Control Partnership guidance supports a clear sequence:
Install temporary support first.
Remove the wall and fit the beam or lintel.
Have the steel and its bearings inspected while still exposed.
Only then close up the ceiling and make good.
One common avoidable mistake is letting plasterboard or finishes cover the steel before the inspector has seen it. Agree this in writing with your builder, and make sure inspection visits are booked around the programme.
Planning permission and Building Regulations
These are two separate checks, and people mix them up.
Planning permission. Local-authority guidance, such as Rother District Council’s FAQs, says internal reconfiguration of a dwelling, including removing internal walls, will not normally need planning permission. The exceptions are the ones to check: listed buildings, flats and maisonettes, leasehold properties, conservation-area constraints and anything that changes the exterior. If you are also changing the outside of the house, our guide to permitted development rights is a useful next read.
Building Regulations. Planning Portal states that building regulations will normally apply when you remove an internal wall or form an opening in one. A genuinely non-load-bearing partition may not need approval in some circumstances. But work that affects structure, fire escape routes, ventilation, drainage or electrics needs professional assessment.
In practice, the usual process is:
Get structural calculations where required.
Submit a Building Regulations application or notice before work starts.
Arrange inspections while the work is exposed.
Receive a completion certificate after a satisfactory final inspection.
For straightforward minor domestic jobs such as removing one or two walls, councils often describe a Building Notice as suitable, while more complex work may need full plans. Your local authority or an approved inspector will tell you which route fits. Keep the completion certificate: a buyer’s solicitor will ask for it when you sell. We explain how this works in more detail, for loft projects, in our guide to securing a completion certificate.
Fire safety and the open plan kitchen
Opening up a ground floor can change the escape route from upstairs rooms. If the kitchen now opens onto the hall or stairs, you may need to review fire separation, smoke detection and escape. This is exactly the kind of knock-on that official guidance means when it lists fire escape routes among the things to assess. Raise it with the engineer and Building Control at the outset, not after the wall has gone.
Leasehold, flats and party walls
If you own a flat or a leasehold house, the lease may restrict structural alterations. For example, Croydon Council’s leaseholder guidance lists removal of an internal wall among alterations that need written approval for its leaseholders. That is specific to that council’s leases, not a universal rule, so read your own lease and ask your freeholder before you spend on drawings.
If the wall you want to alter is shared with a neighbour, or the beam will bear on a shared wall, the Party Wall etc. Act 1996 may apply. Our party wall agreement playbook walks through the steps, and it is worth reading before you finalise the design.
What a knock through costs
Published guides vary a great deal because the scope of work varies. Treat all of what follows as budgeting ranges, not quotes.
Checkatrade’s open plan living guide gives around £975 for a single doorway opening in a load bearing wall and around £2,375 for a large open plan opening, before extras.
Its separate load bearing wall guide notes that a kitchen and dining room wall can cost more than other walls, because pipework and electrics may need rerouting.
Other 2026 guides we reviewed put a typical complete load bearing knock through anywhere from about £2,500 to £8,000, depending on span and finish.
That spread is not a contradiction. It reflects what each guide includes. A headline figure often covers the engineer, steel and labour, while the rest comes later.
Items that commonly sit outside the headline price
Item | Why it matters |
Structural calculations | Needed for the beam design and Building Control |
Steel, padstones, posts | Cost rises with span and load |
Temporary propping | Essential for safe removal |
Building Control fees | Application or notice, plus inspections |
Electrics and plumbing | Sockets, switches, radiators and pipework often sit in the wall |
Extraction and lighting | An open kitchen may need better ventilation and new lighting |
Plastering and ceiling repair | The beam and the removed wall leave a lot to make good |
Flooring transitions | Floor levels and finishes rarely match across the old wall line |
Decoration | Often a whole-room repaint |
Skip hire and waste removal | Brick, plaster and dust add up quickly |
Published guidance specifically warns that steelwork, electrics, plastering, decorating and flooring can raise the final cost materially. If a quote lists only “remove wall, supply beam”, ask what happens to everything on the list above.
When a knock through becomes a bigger project
Often the wall is the start of a wider scheme: a new kitchen, a rear extension, or a garage that becomes part of the living space. Our published starting prices for those projects are:
Garage conversions from £14,000
Garden rooms from £18,000
Single and double storey extensions from £45,000 to £85,000
Loft conversions from £35,000
Those are for complete projects, not for a standalone wall removal. If you are weighing a knock through against an extension, ask for both to be priced so you can compare what you gain for the money.
How to brief a builder so quotes compare fairly
A quote is only as good as the brief. Before you ask anyone to price, give each builder the same information:
The engineer’s drawings and calculations, or confirm that the builder will arrange them and say who pays.
The extent of the opening, with the position of any returns or posts.
Who handles Building Control, including fees and inspection bookings.
Service alterations: which radiators, sockets, gas or water pipes and the extractor need moving.
Finishes: plaster skim, ceiling, floor repairs and decoration, room by room.
Dust and access: how the builder will protect the rest of the house, and how long you will be without a kitchen.
Then compare like with like. Ask each contractor how they will prop the structure, how they will keep the steel visible for inspection and what they will do if the wall turns out to contain something unexpected, such as a flue, a pipe run or an old lintel in poor condition.
Our view: treat it as design and compliance, not demolition
We build loft conversions, extensions, garage conversions and full renovations across Greater London and Essex, and open plan work is part of almost every one of them. The pattern we see is consistent: the wall coming down is the quick part. The decisions that decide whether the project goes smoothly are made before that, on paper.
Three habits make the difference.
Decide the sightline first, then the steel. Standing in the room with the engineer and showing exactly where you want to see from one end to the other usually produces a better design than asking “what is the cheapest beam?”. A slightly shorter opening can save a lot of steel and finishing.
Ask for the price in lines. We believe a quote should show structure, services and finishes separately, so you see where the money goes. That is also why we promise detailed quotes within 24 hours: you should not wait weeks to learn what a job involves.
Look at real work. Anyone can describe good site management. We let clients see live projects through virtual tours before they hire us, so you can judge propping, tidiness and workmanship on a real job rather than on a brochure.
— Florin
Working with EvoStruct
If your knock through is part of a wider plan, such as a kitchen extension, a garage turned into living space or a full renovation, we can handle design, structural coordination, party wall matters and project management from planning to completion under a fixed-price contract. Start with our residential building services page, or send us your drawings and we will come back with a detailed quote within 24 hours.
Common mistakes to avoid
Judging a wall by looks. No single clue proves it is safe to remove.
Starting work before notifying Building Control. Removing a load bearing wall is notifiable, and applying afterwards causes delays and can create problems when you sell.
Covering steel before inspection. Keep it exposed until it has been checked.
Forgetting services. A radiator, boiler pipe or consumer unit run on the wall can change the whole programme.
Ignoring the lease. Leaseholders should get written consent first where the lease requires it.
Underestimating finishing. Plastering, flooring and decoration are real costs and take real time.
FAQ
Can I remove a load bearing wall myself?
We would not advise it. The wall has to be supported temporarily, replaced with a beam or frame designed by a structural engineer, and inspected under Building Regulations. Building Control guidance treats taking down a load bearing wall as notifiable work, so you need to apply before starting.
Do I need planning permission to knock through?
Not normally for internal changes to a house, according to local-authority guidance. Flats, leasehold homes, listed buildings and conservation areas can bring extra requirements, and Building Regulations are a separate matter that usually applies.
How much does it cost to knock through a kitchen and dining room?
Published UK guides range from about £975 for a single doorway to several thousand pounds for a wide opening, before electrics, plastering, flooring and decoration. Your own figure depends on the span, the steel and the finishes, so get itemised quotes based on an engineer’s design.
How long does a knock through take?
The structural stage is often a matter of days, but design, calculations and Building Control notice come before it, and making good and decoration come after. Ask your builder for a programme that shows each stage and the inspection points.
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