Are you a main contractor looking to save time when installing a below-ground substructure?

If you’re like many of the clients who approach us, you may be fed-up of below-ground construction methods (such as in situ) taking so long.

After all, the longer below-ground construction takes on-site, the higher the risk in terms of resulting in a substandard product, and going over programme.

But what if I told you that you could actually save up to 70 – 80% of time spent on-site?

That’s right; the title is no joke.

As a subcontractor who specialises in prefabricated steel substructures, I’m going to explain how this innovative method works and how you could benefit from it.

An introduction to prefabricated steel and how it works

If your construction project requires a hole in the ground – like a cellar, lift pit, vehicle maintenance pit  or intercepter tank – or anything else which requires a sump or pit as part of a bespoke facility, you’ll be faced with the challenge of constructing below-ground.

That’s where prefabricated steel substructures come in. They’re manufactured entirely out of steel, in an off-site facility – or factory environment. This makes for a far more innovative and effective method of constructing below-ground.

Once your prefabricated steel substructure is complete, it’s then transported to the site, before being fixed into position, then back-filled with concrete between the earth and the substructure.

The best thing about this is that having been specified upfront (ideally around six weeks, but this varies), your prefabricated steel substructure will be ready to go once you start on-site.

So, what would take weeks or even months to complete with the likes of in situ, could be done in just a matter of days.

It also eliminates the risk of leaking, and can be built to extremely tight tolerances. This is why many main contractors who know about this method tend to stick with it.

How to save time with a prefabricated steel substructure

Want to ensure you can save on your on-site installation time with a prefabricated steel substructure? It works a bit differently than what a lot of main contractors are used to – but the benefits far outweigh the cons.

In an ideal world, the best way is to approach a specialist subcontractor in the early tender or design stage of a project. Although I know this hardly ever happens, and usually our clients come to us after the project has been specified for in situ or precast – to which we then offer an alternative.

However, if you engage with a subcontractor who specialises in prefabricated steel in plenty of time, they should be able to listen to your needs, talk you through your options and manufacture your substructure – entirely bespoke to your needs – in around four – six weeks’ (this will vary depending on the project and how busy the factory is).

Hypothetically, when it’s time to install your substructure, it could be done in as little as seven days.

Advice from a specialist subcontractor

The best advice I can give you is to approach a specialist subcontractor in plenty of time (if possible) to discuss your project with them. They should ask you all the right questions, and take the time to understand the reasons for taking the below-ground activity off-site.

You should also be able to see examples of their previous work, and customer testimonials for extra peace of mind.

Once you’re ready for a quote, this can take around five working days. A subcontractor specialising in prefabricated steel will take the following information to complete a thorough quote, with no exclusions or assumptions:

  • Substructure drawings – including all the required dimensions
  • A ground investigation report for the area they’ll be working in
  • Structural information, including:
    • The loadings of adjacent structures to the substructure
    • The structural specification of how the substructures is to perform
  • Site drawings, so they can understand access to the area of the site
  • The site location
  • Any further logistical parameters they have to work under, including:
    • Site working hours
    • Noisy working hours
    • Special health and safety requirements etc.
  • A scope of works. Many clients wish to excavate themselves, allow the subcontractor to install the structure and then provide the subcontractor with their concrete to install. If you can list out what you need your subcontractor to provide as a service, they can usually work to fulfil your requirements

Don’t have all the above information? A quote could still potentially be drawn up, however it may include some assumptions or exclusions.


I hope this blog has been helpful when looking to save on your on-site installation time. Prefabricated steel is an innovative below-ground construction method that vastly saves time on-site. However, you must be able to approach a specialist subcontractor in plenty of time – ideally in the tender or early design stages of your project.

Do you have any more specific questions about how to save time on your project? Let me know in the comments’ section – or get in touch with me directly. I’m all ears!