Building Restoration

Survey and diagnosis

Preliminary Survey and Diagnosis


Hammer testing for soundness
This initial survey and diagnosis provides the information which will form the basis of the repair activity. It is, therefore, absolutely essential that these operations be carried out by suitably qualified and experienced personnel.

Independent professional organizations exist to carry out this work. Wherever possible, the use of an independent testing company is recommended to confirm the reasons for damage. It is important to do this even when the initial survey to determine the extent of damage can only be undertaken in conjunction with the specialist repair contractor.

Covermeter survey to determine
depth of steel reinforcement
The first step is always to conduct visual examination of the damaged structure, noting all symptoms and recording with photographs. This should then be combined with testing, using principally non-destructive techniques onto cleaned concrete in order to determine the following:
  • Strength of concrete (rebound/schmidt hammer).
  • Depth of concrete cover and reinforcement location (covermeter).
  • Depth of carbonation zone (chemical indicator test, such as phenolphthalein).
  • Chloride content (by weight of cement).
  • Concrete permeability (initial surface absorption test).

A number of other test procedures, e.g., petrographic examination, electropotential mapping, etc., may also be useful in compiling a complete picture of the structure, the damage and the causes.

It is important that the structure is assesed as a whole; of particular importance are the soundness of existing waterproofing systems, evidence of structural movement and structural integrity.

Carbonation depth testing
with phenolphtalein
These will determine the order in which the works should be programmed and if additional or separate works are a prerequisite. This would include the rewaterproofing of balconies, decks or roofs prior to start.

The results of all these tests require skilled and accurate interpretation-so that any unusual aspects of the concrete, the rest of the structure and the environment do no go unnoticed.

Consequently, this diagnosis should be made only by personnel with suitable experience in concrete and its deterioration. In all cases it is recommended that this be undertaken under the supervision of an experienced and independent structural engineer.

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