Do you want to know more about in situ poured concrete and whether it’s right for your project?

If so, then this is probably the blog for you. If you’re new to constructing below-ground, and you need a substructure, in situ concrete is the most traditional and well-known method. 

However, it’s not the only option. There are also some newer, more innovative methods that can provide more reliable results (but we’ll get to that later).

So, how do you know if in situ poured concrete is right for your project?

Well, as a specialist subcontractor, I’m going to explain more about in situ, and how to determine if it’s the best method for you, below.

What exactly is in situ poured concrete?

In situ poured concrete has been long-established as the most common method of building a below-ground substructure; for over 100 years, this is what most construction companies have been using.

So, let’s take a closer look at this method. It means essentially excavating a large hole, and carrying out the entire construction method on-site. Sometimes, very minimal components are fabricated or constructed off-site.

Occasionally the reinforcement and shuttering is modular and can be delivered part-assembled. The steel reinforcing and timber shuttering is all taken to the site, before being pieced together with steel fixers and carpenters, before the concrete can be poured between the shuttering.

Waterproofing is then applied to your completed substructure – or you may use a waterproof concrete.

The pros of in situ concrete:

  • It’s usually more affordable than other methods
  • It can be an extremely effective method when properly constructed
  • It’s a well-established method used for over 100 years
  • It works well on substructures that are on a large scale

The cons of in situ concrete:

  • It can leak once constructed, due to reduced skill levels and on-site quality control during the construction process. The problem then has to be investigated which involves excavating earth and possibly removing internal finishes.
  • It’s labour intensive on-site work – and can take a long time. As well as waiting for the concrete to cure before you can can load it.
  • This method can easily be constructed to a tolerance of  +-20mm
  • It requires a large excavation site for your team to work safely
  • Quality control on the finish is not assured
  • It often creates a lot of waste
  • Problems can occur if batches of concrete are mixed up. I.e. the wrong concrete mix is supplied during the concrete pour by the plant. This issue is only discovered after 28 days when the cube tests are completed and may lead to sections of concrete having to be broken out.

What makes in situ the right choice for a project?

Most people take on the ‘better the devil you know’ attitude when it comes to in situ. It’s what they’re familiar with – even if they may have had problems with it in the past. Generally, it does the job, and it’s cheap.

In essence, if you need your substructure fairly cheap (£500 – £2,000 per sq. metre), and for the job to start on-site quickly, as a design from an engineer has already been completed, then you should look at in situ.

It’s also sometimes the only way; for example, if your substructure is on a large scale (like the size of a tennis court).

However, if you’re keen to have a substructure that doesn’t leak, and time and tolerance is more important than costs, you should consider an off-site approach, such as a manufactured prefabricated steel substructure.

To get a better idea of how in situ compares to off-site approaches, check out our blog: ‘Traditional In Situ Below-Ground Construction vs Off-Site Approaches’.

TIP: If you’re still not sure if in situ is the correct approach for your project, I’d recommend seeking advice from a specialist subcontractor or engineer. They should be able to advise you further.


I hope you’ve found this helpful when learning about in situ poured concrete as a method of below-ground construction. It may be the most common method of below-ground construction, but that doesn’t automatically make it the best for your project.

Do you have any questions about in situ poured concrete and how it compares to other off-site approaches? If so, feel free to leave me a comment or get in touch with me directly. I’d be happy to help.