Are you a main contractor who’s fed up of dealing with cracks in precast concrete substructures?

If you’re like many of the clients who approach us, and think a below-ground construction method that you can be 100% sure won’t crack is merely a myth, think again.

I’m not saying all precast (or in-situ) concrete substructures will crack… but, there is a way you can eliminate the risk of cracking – and leaking – for good.

As a specialist subcontractor, I’m going to explain about a little-known method you may not have heard of before; prefabricated steel substructures.

But first…

What are prefabricated steel substructures?

Prefabricated steel substructures are an innovative, newer approach to below-ground construction. They essentially eliminate all the common issues you’d normally experience with in situ or precast concrete, as they’re manufactured entirely out of steel.

This means they:

  • Won’t crack like concrete does
  • Won’t leak (due to being built from prefabricated steel)
  • Can be built to very, very tight tolerances (+-3mm-4mm)
  • Can cut down your time on-site by 70 – 80%

The manufacturing process takes place in an off-site factory environment that’s clean and constantly monitored. Afterwards they’re transported to the site, fixed into position, and then back-filled with concrete between the earth and the steel substructure.

There are a lot of companies who haven’t yet caught up to the idea of prefabricated steel – despite it having been around for 35 years. It’s particularly good for high water table areas, as it’s similar to the way the hull of a boat is constructed.

Also, what’d usually take weeks if not months to complete, could be done in just a matter of days. The less time you have on-site, the less that can go wrong – am I right?

How to eliminate the risk of cracking

The risk of cracking with precast concrete can theoretically be avoided by following the best practices in mix design and production. However, can you ever be 100% sure your (precast) concrete substructure will be completely free of cracks?

If – and I suspect – the answer is ‘no’, here’s what you should do instead.

The best way to eliminate the risk of cracking with precast concrete is to consider all of your options carefully. If possible, (and you think it might be suitable for your project) approach a subcontractor who specialises in prefabricated steel well ahead of your project (by at least six weeks’).

They should be able to listen to your needs and offer you a quote based on the information you can provide about the job. It can never hurt to look at all of your options – even if the project has already been specified for precast concrete.

Advice from a specialist contractor

If you think a prefabricated steel substructure could be a good alternative to precast concrete for your construction project, I’d advise seeking out a subcontractor who specialises in prefabricated steel. They should be able to offer you free, impartial advice. And, like I mentioned above, provide you with a quote.

A lot of clients are a bit hesitant when they first come to ask, and want to know if it’s really possible to build their substructure out of prefabricated steel off-site. Usually, the answer is a firm ‘yes’, so you shouldn’t be afraid to ask.

However, the main consideration to think about, is how your substructure will be used. Will it need to be fitted out for a specific purpose? Might it be fully submerged in water, or in a high water table area? Will it require any fixtures or fittings? Could mild steel, then rubber-protected paint be a more economical option than stainless steel?

These are all important things to think about when choosing the best method for your below-ground substructure.


I hope this blog has given you a better idea of how to avoid cracking for your below-ground substructure. Regardless of how closely best practices are followed, you can never be 100% confident that your precast substructure won’t leak – potentially leading to your project going over programme.

Prefabricated steel is a great alternative to (precast) concrete, however it is a very different way of working. I’d recommend contacting a specialist subcontractor well in advance – preferably in the early design stages. They should be happy to help talk through your options.

Do you have any questions about prefabricated steel substructures and whether they’re the right choice for your project?

Feel free to leave me a comment below – or alternatively, get in touch with me directly. I’d be happy to help!