It’s no secret that most traditional below-ground substructure methods tend to leak.

But that doesn’t mean it’s not a source of major headaches for main contractors and preconstruction teams – am I right?

As a specialist subcontractor, I know how stressful it can be to get a project completed on programme. And once it’s completed, you can’t be entirely confident it won’t leak.

But what if I told you there was a better way?

Below, I’m going to go over the two most common ways of constructing below-ground, and why they leak – before introducing you to a much better alternative.

Why do in situ and precast concrete methods leak?

Traditional in situ concrete is the way most substructures have been built for the past 80 – 100 years. However, once constructed, it can be prone to leaks. This tends to be due to the reduced skill level and on-site quality control whilst the construction process is underway.

As a result, you often have to go back and investigate the problem – involving excavating the earth and removing internal finishes.

Precast concrete is an alternative that’s suitable if your substructure isn’t on a large scale. It’s quicker than traditional in situ, and is manufactured off-site. However, the process of curing the concrete can lead to cracking, which also means that leaks can occur.

An alternative that won’t leak for up to 100+ years

Glad I caught your attention there. There IS an alternative to traditional methods of below-ground construction, and it comes in the form of prefabricated steel. Substructures made from prefabricated steel are manufactured in an off-site factory environment. They’re made entirely out of steel.

Once ready, they’re then transported to your site, fixed into position, and then back-filled with concrete between the earth and the steel substructure. It’s a unique method that involves using steel plate to construct the substructure, before it’s welded together. Think of it as similar to the hull of a ship – it’s entirely watertight and is guaranteed not to leak

This easily makes prefabricated steel the best option to avoid water ingress – particularly for areas with a high water table. Not to mention, it can stand up to very, very high tolerances (+-3mm/4mm), lowers long-term maintenance costs, and reduces time spent on-site by 70 – 80%. 

TIP: Wondering how we know prefabricated steel lasts up to 100+ years? Read the report by Dr J.P. Bloomfield to find out.

Advice from a specialist subcontractor

Feeling unsure about whether prefabricated steel is really good enough for the job? If you want to set your mind at ease, I’d recommend talking to some companies who have used this method on their construction jobs, and ask them about the final product they were left with. They might be able to give you a good referral.

I’d also recommend speaking to a subcontractor who specialises in prefabricated steel. They should be willing to give you some free, impartial advice, and provide you with a quote based on the specifications of your project.


So, there we have it! In situ and precast concrete substructures often end up leaking due to the reasons above. However, with prefabricated steel, you can be sure your substructure won’t leak for over 100 years. It also has various other great benefits, and can stand up to incredibly tight tolerances.

Do you have any specific questions about prefabricated steel and water ingress? Let me know in the comments’ section. I promise I’ll answer!