Are you wondering about the reason why prefabricated steel substructures won’t leak?

If you’ve heard of prefabricated steel – perhaps from someone in the industry – then maybe you’re curious what all the fuss is about.

Or perhaps this is the first time you’re hearing about it, and I’ve piqued your interest. Especially if you’re used to doing projects in high water table areas, and have had bad experiences with precast or in situ concrete in the past.

As a specialist subcontractor, I’m going to tell you more about the reason prefabricated steel substructures won’t leak like more traditional methods.

So, let’s get started, shall we?

What are prefabricated steel substructures?

It might be good to start at the very beginning – especially if you’re new to the concept of prefabricated steel. This is essential a newer, more innovative approach to below-ground construction. As you might have guessed, prefabricated steel substructures are manufactured entirely out of steel.

This is done using an off-site factory environment that’s clean, controlled and closely monitored – it’s also  certified to BS EN 1090 (i.e. a Construction Product Regulation hEN1090) with code 2 certified welders.

The manufacturing process involves the construction of steel plates, and the necessary strengthening to build substructures. Once your substructure it’s ready, it can then be transported to your site, and fixed into position before being back-filled with concrete between the earth and the structure.

TIP: Check out our blog: ‘What is Steel Prefabrication Below-Ground?’ to find out more.

What makes prefabricated steel completely watertight?

The method used to construct prefabricated steel substructures involves using fully-welded steel plates. This means that your finished substructure is constructed similarly to the hull of a ship So, in contrast to precast and in situ methods, it won’t be susceptible to cracks and leaks.

It also eliminates the risk of water ingress over time. How much time, you ask?

Well, to get a better idea, we employed an unbiased expert in the corrosion of steel in concrete, Dr. J Bloomfield, to find out! His report confirmed that the method used to construct prefabricated steel means it should last at least 100 years in the ground (around 120+, to be more precise) even in the most acidic conditions.

So, you should be fairly certain that your prefabricated steel substructure should stand the test of time! You can also wave goodbye to long-term water ingress issues!

NOTE: Your chosen subcontractor should be certified to CE certified to BS EN1090-1:2009 (as mentioned above). This will ensure your prefabricated steel substructure has been constructed and can be used as a structural component.

TIP: Read more about this subject in our blog: ‘How Can You Build a Substructure That’s Proven Not to Leak?’

Advice from a specialist subcontractor

There are other options in terms of helping your below-ground substructure to remain watertight. However, the likes of Sika concrete or concrete with a waterproof membrane tend to have a lifespan of around 10 – 30 years.

If you’re looking for a more long-term solution, that will completely eliminate the risk of cracking and leaking, as well as one that saves you time on-site and can stand up to much tighter tolerances (+-3mm-4mm), then I’d recommend prefabricated steel as an option.

However, it’s important to bear in mind that this is a different way of working. If prefabricated steel seems like the best option for you, I’d recommend approaching a subcontractor who specialises in prefabricated steel at least six weeks in advance. Or, if you just want to find out more about your options, they should be happy to provide you with some free, impartial advice.


Thanks for reading. I hope this blog has shed some light on why you can be confident prefabricated steel substructures won’t leak. There are many benefits of this newer, more innovative approach to below-ground construction, but this has to be one of the biggest.

However, it can also save you 70 – 80% of time on-site, stand up to very tight tolerances, and can even help to solve the challenge of unskilled labour to build in-situ concrete substructures (as prefabricated steel subcontractors can take on the full risk of the installation).

Just ensure you approach a specialist subcontractor as early as possible (ideally in the design stages) so that prefabricated steel can be incorporated into your construction programme.

Do you have any questions about the watertightness of prefabricated steel? If there’s anything I can help clear up for you, let me know in a comment below. I’d be happy to help!