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Last updated on May 29th, 2023

RSJ cost guide

An RSJ is what will make sure your extension or conversion stays standing. For any major structural work or removing load-bearing walls, you'll need to budget for Rolled Steel Joints (RSJ).

Why install an RSJ?

They can provide essential structural support for constructing new builds and extensions, forming part of the skeleton of the building.

Or, for those looking to remove a load boarding wall (such as extending a kitchen and dining room), they can provide the same support as the wall that’s been removed.

The cost of this structural steelwork can vary significantly depending on your project: from the size of the RSJ to the area of the existing wall to be removed (if required).

How much do RSJs cost?

This guide features the estimated RSJ costs across the UK. Wherever you’re located, they will likely differ from these costs. Only use this as a rough ballpark cost.

Steel RSJ costsCost + VAT
(Range low - high)
Average cost
RSJ beam cost 1m - 5m (up to 46kg)£200 - £950£575
RSJ installation 1m - 5m (up to 46kg)£300 - £750£500
RSJ cost (per kg)£2.50 - £4.50£3.50

Our costs are ballpark averages – get a local tradesperson to quote now

A single doorway (approx. 1m and up to 46kg/m of the beam itself) RSJ beam costs £200 for the materials and £300 for the installation.

By comparison, a much larger RSJ (approx. 5m and up to 46kg/m of the beam itself) costs £950 for the materials and £750 for the RSJ installation cost.

For the prices in this guide, we have considered the following:

  • Steelwork prices assume steel beams or posts only without plates or fabrication.
  • Prices exclude any padstones or piers.
  • Prices assume steels are installed from the underside of joists.
  • No allowance for cutting in joists into the flange of the joists.
  • Prices exclude any lifting or propping.
  • Prices exclude any removal of walls etc.

RSJ cost per metre

Alongside calculating the length of RSJ that you will need, an equally critical calculation is to determine how much weight the RSJ will need to support. The RSJ cost per metre you pay will mainly be dictated by this. As such, you can expect to pay an average of £3.50 per kg when calculating the RSJ cost per metre.

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Types of RSJ

One great feature of RSJs is that they offer the maximum load-bearing support, with the minimum amount of steel. They are available as single beams, double beams, and in a range of distinctive shapes including:

  • I beams: Often RSJ’s are called ‘I beams’ as this is a standard beam shape. They are shaped like an I, with a flange at the top and bottom.
  • H beams: Although similar to I beams, H beams are wider in shape and better suited for longer lengths.
  • T beams: So named as they do not have a bottom flange. These are cheaper but not as strong as I or H beams. They are sometimes called ‘flange beams’.
  • C-section beams: Also known as ‘channel beams’ these look like an upside-down U.

RSJs can be cut to any size and are designed to support a wide variety of weights. Based on the calculations of a structural engineer, your builder will be able to source the correct type of RSJ for your project and ensure you pay a fair cost for your steel RSJ.

You can also consider concrete lintels as an alternative to steel lintels. However please note that although they are cheaper, they are not recommended for load-bearing over large spaces.

Steel RSJ costs

Factors affecting RSJ costs

  • Size of beam: Your steel RSJ costs will be calculated based on the length of the beam, the thickness of the beam and the amount of weight it will need to support.
  • Utilities: If you’re removing a load-bearing wall then you may also need to move any electrics, gas, plumbing, radiators, power sockets and lighting. View our electrician hourly rates guide and plumber costs guide for further details.
  • Knocking down any walls: Unless you are working on a new build or house extension, you’ll likely be removing a wall at the same time as installing an RSJ. For more information view our guide on the cost to remove a load bearing wall.
  • Accessibility: How accessible your home and the room are will affect the cost accordingly. Even moving an RSJ a small distance can be a very complex job.
  • Finish: One way to save money on RSJ costs is to finish the room yourself. You’ll still have to pay for the structural engineer, RSJ beam cost and RSJ installation cost, but you’ll reduce the overall cost by doing any plastering and painting.
  • Skip hire: Installing an RSJ creates a lot of waste, especially if removing a load-bearing wall. As such, you’ll need to hire a skip to dispose of any waste. Our skip hire cost guide can help you determine exactly what’s needed.

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RSJ beam installation cost

RSJ checklist

RSJ projects are not simple. At almost every stage of the project, there are considerable risks. As such, we recommend you check all of the below is in place:

  • A highly qualified builder: To ensure the structural integrity of your home is maintained, we recommend you hire an experienced builder. This is by no means a job you should skimp on when it comes to the installation or RSJ cost. It’s also a dangerous job due to the weight of the RSJ and the removal of materials.
  • Structural engineer: Next, you’ll need to get in touch with a structural engineer, or see if your builder has one in-house. They will ensure the RSJ support is adequate for the intended load, removing any risk of damage to your home. A structural engineer will typically cost £250 for this project. For more information view our structural engineer cost guide.
  • Building regulations approval: Any structural alterations need building regulations approval, so you will need to secure this. Your structural engineer can help provide the necessary plans, which can then be submitted to your local authority. Further details can be found in the official guidance.
  • Party wall agreements: If the RSJ will rest within a neighbour’s wall (also known as a party wall) then you will need to secure a party wall agreement with any affected neighbours. This helps prevent future disputes that can be incredibly costly.
  • Accommodation: Lastly, you may want to consider vacating the property and staying at a hotel, or with family, whilst the work is done. A lot of dust and noise will be created, making for a potentially unsafe and disruptive environment.

Can I install an RSJ myself?

It is highly recommended you do not attempt to install an RSJ yourself.

To find a local, reputable, tradesperson in your area and get RSJ beam and installation costs use our free search feature.


How much does an RSJ cost?

RSJ costs are based on the cost of the beam and the cost of the installation. For a beam that weighs up to 46kg per m, you’ll pay between £200 for the beam and an additional £300 for the installation. Prices will vary based on the size of the beam and the support needed.

How much do RSJ beams cost?

If you’re just looking to purchase the materials, then RSJ beams cost around £575 on average. This is based on a 3m beam weighing 46kg/m.

Do I need planning permission to install an RSJ?

Although building regulations approval is needed, you are unlikely to need planning permission unless you live in a listed building. If in doubt, check with the planning department to ensure you’re up to date with the latest regulations.

Key takeaways

  • RSJs provide the support needed for new builds, extensions and removing load-bearing walls.
  • RSJs have a variety of names and styles – lintels, I/H/T beams, channel beams and more!
  • You’ll need a structural engineer and a qualified builder to secure building regulations approval.
  • The price you pay for an RSJ is based on the size and support needed.


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Working with professional estimators, we collate cost estimates for the common home improvement and repair jobs in the UK.

All the costs are estimates only. For accurate costs for your particular requirements, you are encouraged to reach out to professional tradespeople to receive a quote for your job.

Our estimators are Chartered Members (MRICS) of the Royal Institution of Chartered Surveyors and Members of the Chartered Institute of Building (MCIOB). See full disclaimer.

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Hi David, thanks for the comment. We would recommend that you speak directly with a Structural Steels expert near you. You can find them by clicking HERE and then entering your postcode into the search.

David Forshaw

I am looking to install a 6 metre bi-fold door and require a 300 x 300 x 12 x 8 metre RSJ.How much would this RSJ cost me?

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