The materials functions have been seriously overhauled for Revit 2013.
On the Structures side, a new built-in parameter 'Structural Material' has been introduced.
This parameter is non-modifiable and non-removable. It can only be altered from 'Instance' to 'Type' and vice-versa. The function is by design and appears to be for the purpose of using extended information for calculation and to provide a more fixed and stable platform in the structural model for third party analysis software linking
When family files are updated in Revit 2013, the upgrade elbows out any existing material parameter and replaces it with this.
However, we have discovered a slight complication with this. Take specifically families which have a nested component, and the material parameter in this nested component is linked to a material parameter in the host.
If you open the family file directly in Revit 2013, the upgrade process will 'sever' this link, but it will upgrade.
If you are upgrading a project that contains such a family, the upgrade will fail for these elements and Revit will require that these are deleted from the model before continuing. This is happening here with our Pile Cap families, which have a Pile family nested inside.
To get around this, you have to open the project model in the previous Revit version and edit the offending families to de-couple the material parameter link. The model will now upgrade in Revit 2013. You can now re-edit these families to re-couple the parameters, then reload back into the model. You may also want to consider changing the previous material parameter to the new 'Structural Material' to take advantage of the new functionality
I trust this helps and is clear, but please feel free to comment
