@43d7c4ea @6c09e7e6 My understanding is that the main problem with RAAC is water ingress, which rusts the rebar. With normal concrete that is visible, because the rust swells and cracks the concrete (you’ll probably have seen that ‘spalling’ on the seafront somewhere). With RAAC, the swelling is absorbed by the aeration, causes lost adhesion, and never manifests on the surface, so it’s vital to fix water ingress asap, and to monitor carefully any beam that has got wet. 

 @7db1d990 @6c09e7e6 

which tends to support the cost-cutting installation argument (?) 

 @43d7c4ea @6c09e7e6 Exactly! I didn’t have room in the post to add that. Poor design, poor maintenance, it’s one or the other. The dual sins of building with flat roofs, then not looking after them is likely to be a huge contribution to this particular crisis.