Looking for the best way to construct and install tanking as a waterproofing method below-ground?

If you need a waterproofing method for your below-ground substructure such as tanking, you may already have a good idea of some of your options.

However, there may be a more innovative method you haven’t heard of yet, that completely eliminates the need for secondary waterproofing and guarantees a completely watertight outcome for your project.

As a subcontractor specialising exclusively in something called prefabricated steel as a method of below-ground construction, I’m going to tell you why it’s a much better alternative to in situ or precast – and why it eliminates the need for tanking entirely.

But first…

What is tanking and why is it needed?

Tanking is a method of waterproofing applied to the inside of a below-ground substructure. Once your structure is built, you then fix membranes to the walls and behind the plasterboard. This diverts any incoming water into a chamber which will then pump the water away.

This is what’s known as a secondary method of waterproofing and is completed to divert the water coming into a leaking substructure that’s built from either in situ or precast concrete.

So, in other words, if you need this method of waterproofing for your substructure, your system has already failed.

You may find yourself wondering: “How can I avoid this altogether?”

Well, there is a way – and it means that a secondary waterproofing method such as tanking isn’t needed at all.

A better way to make your substructure completely watertight

Now, onto prefabricated steel. This is essentially a newer, more innovative approach to below-ground construction, and these are substructures manufactured entirely out of steel in a clean, off-site factory environment.

They’re built under tightly controlled conditions, and closely monitored – they’re also certified to BS EN 1090 (i.e. a Construction Product Regulation hEN1090) with code 2 certified welders.

Using fully-welded steel plates, the substructures are built and welded together, meaning 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.

Hence, no need for tanking!

(I’ve actually gone into much more detail about prefabricated steel and how it’s used in my blog: ‘What is Steel Prefabrication Below-Ground?’ – hopefully it’ll give you a bit more background)

This method even eliminates the risk of water ingress over time, as these substructures will remain in good condition (and watertight) in the ground for at least 100 years (120+ to be more accurate) in even the most acidic ground conditions.

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

TIP: Check out another blog to find out more about other waterproofing options in regards to prefabricated steel.

Advice from a specialist subcontractor

If you’re in need of tanking for your below-ground substructure, I’d recommend speaking to a CSSW (certified surveyor in structural waterproofing) or a large manufacturer of tanking products such as Newton, Permaguard of Visqueen.

However, if you want to know more about prefabricated steel and how to avoid tanking for your project – or future projects – (because it’s simply not needed) then the best advice I can give you would be to contact us to discuss your project and find out more about what’s possible.

Remember, before you start a project, you have options. Not everyone will be automatically on-board with more innovative methods like prefabricated steel, but the benefits far outweigh the doubt of trying new things.


Thanks for reading. I really hope this blog has managed to shed some light on how best to construct and install tanking to walls below-ground level.

However, if you’re looking for a better solution than in situ or precast concrete – that doesn’t require tanking – I’d recommend getting in touch with me directly to find out more about prefabricated steel and whether it could be a good option for you.

Alternatively, if you have any questions, just leave me a comment below – I promise to respond with something helpful!