How much does it cost to knock down a load-bearing wall?

Cost Factors in Knocking Down a Load-Bearing Wall

As we've seen from the above price averages, the size of the wall and the depth of the required RSJ will be the primary elements that dictate the cost of your wall demolition.

However, there are several factors to bear in mind when setting a budget.

Type of RSJ

RSJs (rolled steel joints) come in two variants. An H-cross beam can be up to 100 metres long, whereas an I-beam is smaller, usually between ten and thirty metres.

The difference is that an H-cross RSJ is significantly heavier and can support a much greater amount of pressure, so the size of your property and your structural engineer's report will explain which RSJ is best suited to your home.

Most RSJs cost from £1,600 to £2,000 (including installation), so this makes up the bulk of the cost - the demolition and skip hire are much smaller parts of your quotation.

Waste Removal

Your demolition contractor will usually organise the waste removal for you and include the cost of skip hire within their estimate. If not, you'll need to book a skip separately.

A medium-sized skip costs between £150 and £200 (depending on your location), or you can hire a mini skip for a small wall removal project for around £90.

Large skips for bigger demolition projects cost between £250 and £300 per week.

However, you may need to apply to your local council for a licence, depending on where you live and whether you have space available on a drive for the skip to be placed while the work takes place.

City centres often have parking restrictions, so you may need permission to have a skip on the roadside for several days.

Structural Engineering Costs

Some demolition contractors will recommend a structural engineer they regularly work with, who will come and assess your property and review your plans to knock down a load-bearing wall.

This part of the project is essential because your contractor will need technical calculations to ensure the support beams installed are more than sufficient to replace the load-bearing wall.

Most structural engineers charge around £500 to determine the right specifications for an RSJ. However, if you are working with an architect on a broader renovation plan, they may be able to cover this requirement for you.

Party Wall Agreements

Knocking through a load-bearing wall that is connected to another property means that you will need an agreement from your neighbour before the work can begin.

An informal discussion is normally the best starting point, and you can explain what you're planning to do and why you would like to have a new steel beam fitted to your adjoining wall.

Provided you have a written agreement from your neighbour, you won't need to do anything further.

In some cases, you may need to budget for a steel column since an older property may not have the stability to hold up the higher floors with an RSJ alone.

If so, your contractor will need to complete some excavation work first, which will need to be included in your party wall agreement.

Most party wall agreements are straightforward but can be a significant stumbling block if your neighbour refuses.

The normal course of action here is to hire a surveyor to review your plans and even potentially pay for an arbitration service to decide on the outcome.

The cost of hiring a surveyor to resolve a party wall disagreement is around £1,000, so this is best avoided if possible.

Internal Finishing Work

A load-bearing wall is likely to conceal wiring, plumbing and pipework, along with plug sockets and radiators, so you need to have a good idea of how your finished room will look.

Additional costs to bear in mind include:

• Relocating a radiator, which costs from £170 to £335 depending on the size and type of radiator.
• Hiring an electrician to disconnect old lights or plug sockets and position new outlets in the reconfigured room. Costs start at around £45 an hour.
• The floor will need to be levelled if the floor on either side of the old wall is not aligned. This work costs around £25 per square metre, plus the cost of new flooring.
• Finishing work to the wall, such as replastering, skimming or painting, will cost around £12 to £25 an hour, depending on how much work is involved.

Some of these extra tasks might be things you are happy to take on yourself (such as repainting), but it's best to have a full list of every job and ensure you have priced everything up before you start.

How Will a Demolition Contractor Knock Down a Load-Bearing Wall?

If you've never demolished a wall before, you might like to know what the process will involve - and plan to be away during the major work since there may be a fair amount of dust!

Here's a step-by-step run-through of the demolition process to remove a structurally supporting wall.

• First, your contractor will lay out dust sheets and verify whether there are electrical cables or pipes in the wall. Ideally, it would help if you had these disconnected before the demolition, as they can cause delays and extra costs.
• Once it's safe to begin, the crew will pry the boards back to reach the structure underneath and insert a timber support as a temporary reinforcement.
• Next, your tradespeople will install a set of 'Acrow' props, which look like metal rods with plates at either end. These are normally required at both ends of the wall, with additional braces in the middle when needed.
• When the wall is supported, the contractor can remove door frames and any coving or architraves, followed by the lintel, cement, or concrete above.
• The plaster and brickwork can then be removed from the top downward, with disconnected cables and pipes dismantled as they appear.
• Before the RSJ is fitted, your contractor will place more supports against the rafters and joists and repair holes before the RSJ can be put in place and boxed in.
• Finally, your contractor will repair the ceiling, and your new open place space will be ready to decorate as you wish!

This basic guide follows the usual steps for demolishing a load-bearing wall. Still, it's possible that your job could be much easier or more complex, depending on the size of the wall being removed and the level of support needed.

If in any doubt, you can chat through the process and program of work with your tradesperson and discuss time frames for each stage of the demolition.

Popular Reasons to Knock Down a Load-Bearing Wall

The most common reason to remove a supporting wall is to invite more natural light into your property and remodel the layout of your rooms.

Open Plan Kitchens and Living Spaces

Modern homeowners often wish to create a broader kitchen/diner by removing walls between these two rooms - a larger space is brighter, airier, and more sociable.

It may also be that, in a period property, your kitchen is a very small galley setup at the back of the house. Knocking through the walls between this room and the next gives you the opportunity to increase your kitchen space multiple times over.

Building an Extension

If you are creating extra space by extending outwards, you will often need to knock through the old external wall to allow the new area to be built.

You can do this in stages or have one contractor work on the total build, demolishing walls and building the new structure as one larger project.

Creating New Windows or Doors

New windows, such as picture windows, bifold doors or patio doors, normally require a structural wall demolition because the pre-existing doorway is very likely to be built into a load-bearing wall at the end of your home.

The process is the same as described above, whereby a contractor will remove the brickwork, to be replaced with glazing, and fit a new lintel overhead.

Planning Permission Requirements to Demolish a Load-Bearing Wall

One of the common concerns with knocking through a wall is whether the work requires formal planning permission, which can take several weeks or potentially be refused. A refusal will increase your load bearing wall removal costs so its vital that the application is completed correctly to avoid this scenario.

The good news is that if you're demolishing an internal wall, you are unlikely to need permission unless you own a property with listed building status, or live within a conservation area.

Knocking down an external wall may require consent, although that depends on what you plan to replace it with - for example, an extension or a larger window.

Where the work changes the external appearance of your home, you may need planning permission. However, some work is allowed under permitted development rules, so it's wise to check with your local planning office and an experienced contractor first.

Building Regulations

Building regulations are not the same as planning permission and refer to the statutory standards all contractors need to adhere to when they're working on a residential property.

They cover requirements such as fire safety and the structural stability of the home and set rules about things such as the required supports.

Every building project needs to comply with the regulations, with a survey to verify that there are no deficiencies in the work that put the property at risk of collapse.

When you have a load-bearing wall demolished, you need to apply to the relevant Building Control office for a Building Notice, which is a certification that verifies your wall has been removed and replaced with a suitable support structure.

Inspections cost up to £650 (as a maximum) for walls up to ten metres square.

You will need to submit the calculations from your structural engineer to demonstrate the planned works and receive a Completion Certificate once everything has been signed off.

Keep hold of your certificate, as you will need this if you ever decide to sell - you may also need to submit a copy to your building insurance provider.

Fire Regulations for a Load-Bearing Wall Demolition

The final regulatory consideration is fire regulations - an experienced, accredited contractor will be very familiar with these standards, so can always provide further advice.

When you demolish a load-bearing wall, the work needs to include:

• An RSJ that is resistant to fire for at least 30 minutes, boxed in with two plasterboard layers at least 12 mm thick.
• Calculations from a structural engineer that verify that any timber lintels or beams used are fire resistant to a defined value. Options include treating wood with fireproofing coatings or creating a larger cross-section.
• Coverings and protections to ensure a concrete lintel is appropriately protected from fire.

External doors fitted into your load-bearing wall also need to be self-closing and fire-resistant.

Once you know the cost to knock down a load bearing wall, you may also want to research whether you need planning permission to demolish and rebuild, how much it costs to dispose of waste materials and the cost to demolish a wall which isn't load bearing as an alternative.