Why do I get a Validation Error: Slab/roof overlap?

Tekla Structural Designer 2015i and above will produce a validation error if you have a roof and a slab overlapping.

This is to trap out the possibility of the roof and slab spanning in different directions and thus ensuring that the applied load is decomposed to the correct panel item.

In order to use the integrated Wind Wizard you must 'skin' the building in wall and roof items so that the appropriate zoning and pressure calculations can be performed. The Wind Wizard only 'sees' wall and roof items in the model.

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To ensure that the roof panel only acts with the Wind Wizard you can use the 'Decompose only wind' option via its Properties to decompose only the applied wind loading to the Roof item.

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Once the roof item has been designated to only decompose for wind load once re-validated the issue will no longer exist.