Case Studies | Expansion Joints – Principality Stadium, Cardiff

The Principality Stadium (formerly the Millennium Stadium) is the national stadium for the Welsh Rugby Union. Built in 1999 for Wales to host the Rugby World Cup that year it is approaching 20 years old. It’s hosted Rugby World Cup games, countless rugby and football internationals, both rugby and football’s European Cup finals, the FA Cup final a number of times not to mention concerts by some of the worlds biggest music acts and even monster trucks!


Recently there have been problems with the expansion joints in the concrete, with the old sealant degrading and debonding. This has resulted in water leaking through the stadium in several different places which is causing problems with maintenance. One of our clients were contracted to repair and replace the old sealant. They decided to use our Hyperseal Expert-150 polyurethane (PU) sealant. Using a PU sealant is a great choice for this job for a number of reasons. It has a great deal of elasticity which means it can cope with a the (at times) extreme movement in the stadium as well as the natural expansion and contraction of the concrete. It can also cope with the wide range of temperatures resulting from the cold winters and hot winters that can happen in Cardiff. Expert-150 has  CE Mark and ASTM which makes it the obvious choice for a PU sealant to do this job


The first step was to cut out all of the old sealant, clean the joints and grind down the old concrete to smooth off the cracks and splits. It also allows for a better bond between the PU and the substrate. Once that was done, the concrete was re-primed, a backing rod was applied to the bigger cracks and, finally, Hypersel Expert-150 applied to the joints. You can see from the pictures how bad some of the cracks were and how tidy and solid a finish Hyperseal gave.


This is being trialled for now with a series of international rugby matches planned in the near future. If the joints hold up under that pressure, which we’re certain they will, then all of the remaining joints will be repaired using Hyperseal Expert-150. This is a really prestigious job which we’re delighted to be a part of!

Like This Case Study? Then Give Us A Share:

"Hyperdesmo was the ideal solution for the job. Quick and easy to apply and very reasonably priced too."

Les Smith

LS Roofing

I have used several Alchimica products in the past and I keep coming back to them. Reliable, outstanding performance and fantastic prices. Thanks!

Chris J

CJ Waterproofing

I used Hyperdesmo HAA and Particular on a tricky job which combined with the great advice provided by the team at Alchimica resulted in a successful outcome and a satisfied customer. Cheers!

W Simpson

Simpson & Son Waterproof & Damp Proofing

For more information on our products please get in touch...