Some new and changed features of Revit 2018 result in certain behaviors for upgraded models. Review this information before upgrading your models.
When you upgrade a model with multistory stairs defined using the Multistory Top Level parameter, the stairs geometry is maintained and the component is upgraded to use the new multistory stair functionality. In some cases, a new multistory stair cannot be created for the entire height.
To solve these issues, keep one multistory stair component as a reference and delete the other stair components. Use the Create Multistory Stair tool to select levels and generate a multistory stair from the original stair component. See Multistory Stairs.
When you upgrade a model with railings hosted to stairs, when editing the railing you will not see the new start point and endpoint control grips or the beginning position control when working with a closed loop sketch. To solve this issue, un-host the railing from the stair and then re-host the railing to the stair. See Modify a Railing.
When you create a new model, the Outdoor Air Information setting for zones defaults to From Space Type. When you upgrade a model, the Outdoor Air Information setting defaults to From Zone. See Outdoor Air Information for Zones.
When you upgrade a model with hydronic piping networks, the Simplified Colebrook and Custom Calculation methods are recalculated to use the Colebrook equation.
When you upgrade a model from Revit 2016 or earlier releases, the text measurement used may have an effect on the appearance of text. See Troubleshooting: Text in an Upgraded Project.