Existing building versus new building

Existing buildings were designed in accordance with previous norms, which may be different from those that are currently applied.
Nowadays new buildings are designed in accordance with the Eurocodes. A European standard which specifies how loads and structural calculation should be conducted. In order to comply with the Eurocodes, loads and calculation methods may differ from previous norms. In which case structures built before 2010 may not comply when they are calculated in accordance with the new standards.

To avoid the rejection of existing structures or the high cost involved in upgrades, a specific norm has been developed to evaluate existing building, NEN 8700 standards.

NEN 8700

The assessment of existing structures to ensure their safety may differ significantly in different aspects from new building. For example, the reference period that state how long a structure must last is normally very different from the standard reference period that applies to a new construction.
To determined if a structure is safe in a certain moment, the reference period plays a very important role. In addition, it is possible to measure the existing construction. In this way we can assess the actual parameters of the materials (such a concrete or steel quality) and the applied loads that are used to model the structure.

‘Pros’ and ‘cons’

Our experience assessing existing structures is that:

• Technical standards can be limited when the current requirements are declared applicable;
• No serious deficiencies are noticed in the technical material;
• Deterioration of structural elements lead to strength reduction;
• Higher compressive strength are frequently measured in the concrete. ;
• In accordance with the current knowledge the reinforcement configuration can lead to a different load distribution;
• 3D calculations show reservations that are not found in a 2D approach.