Sea (or salt deterioration) effect

A condition assessment of an existing structure may be performed for a number of reasons:

·   -     Determining whether a structure is safe for public occupancy;

·   -     Documenting the condition of existing structures prior to performing construction nearby;

·   -     Evaluating the existing condition as part of a ‘‘due diligence’’ survey prior to purchase of a                  building;

·   -     Determining whether a structure is suitable for a change in usage;

·   -     Establishing code compliance or determining areas of noncompliance to be remedied;

·   -     Determining the cause and appropriate remedy of problems that elicit tenant complaints,   such as leaks, excessive floor vibrations, or trip hazards.

       

      In these instances, the purpose of a condition assessment is to identify the pervasiveness and severity of distress, defects, and deterioration, if any. Identifying the causes of such conditions is usually necessary to design proper remedies.

Defects

Defects are introduced most commonly during design, manufacture, fabrication, or initial construction; therefore, they are typically present at the beginning of the service life of a structure. Latent defects may be present during initial construction and lie dormant prior to manifesting themselves. 

Deterioration

Unlike defects that are typically present at the beginning of the service life of a structure, deterioration of a material or system is time-dependent. While some forms of deterioration may develop early in the service life of a structure, others are a matter of the aging of a material or system. Deterioration often is initiated or accelerated by the presence of a defect or the introduction of a catalyst. Water is the most significant catalyst for deterioration; approximately half of all failure mechanisms identified in construction involve water, including some subtle interactions

The Effects of Salt Deterioration on Buildings

Many buildings particularly those near the coastal area, are affected by varying degrees of salt deterioration. This is particularly relevant to many buildings which are over 50 years old but can also be relevant to buildings of a lesser age. The main, or common, problems associated with salt deterioration of buildings include the following:

 Mortar to Brickwork and Deterioration of Bricks

The softer lime mortar used in external brickwork prior to the 1960's can be substantially affected by salt deterioration. This is more prevalent in the exposed location but also buildings located 2-3 kilometres from the sea can also be affected over a longer period. The salt has caused disintegration of the mortar and will result in the mortar being a soft powder form.

The salt deterioration can extend through the brickwork either partially or to the full width of the external course of brickwork.

In extreme cases, the mortar will disintegrate and allow downwards stacking of the bricks and eventually collapse of the external walls.

External surface repointing or cement rendering of the building will be structurally inadequate as in the majority of cases the deterioration of the mortar extends all the way through the bricks. Cement rendering will not remedy the problem, as the render will only be inserted into the brickwork to the depth of 10mm maximum and not the full width.

Many of the ancient bricks not salt tolerant and can be subject to surface delamination. This occurs as the salt crystals adhere to the brickwork and are absorbed into the bricks. During rain the crystal will expand and then push the outer surface of the brickwork away and cause surface deterioration. Once the harden surface of the brickwork is lost, then the rate of deterioration of brickwork will accelerate. It is not possible to prevent the surface delamination of bricks and would require replacement of the affected bricks on an individual or whole basis.

Rusting and Deteriorated Wall Ties

the wall construction would involve wall ties. The wall will be exposed to rusting and deterioration and unable to secure the external skin of brickwork to the main building. With complete rusting of the wall ties, this will allow the external brickwork to bow out as it is unrestrained and in extreme cases can cause complete collapse of the external skin of brickwork.

If the brickwork is not bowed, then specialized stainless steel screw fixing can be inserted through the brick walls and can secure the brickwork to the main building. This would only be undertaken if the mortar is in a sound condition. Should the mortar of the brickwork be in a deteriorated condition, and the wall ties known to be rusted, then the only remedy is to scaffold the building and remove the bricks on an individual basis, clean the bricks, relay and reinstall. Specialized stainless steel wall ties will need to be inserted within the brickwork to secure the relayed brickwork to the main building. The extent of deterioration of the mortar and ties can only be determined by an expert in this field.

The presence, or otherwise, of rusted wall ties can only be determined by experts and may involve some part removal of external bricks on an individual basis to examine the condition of not only the mortar but the wall ties which secure the brickwork. The assessment of the deterioration of the mortar to the bricks and rusted wall ties relies upon specialised expertise as well as some investigative site inspections.

Timber Delignification

Various structural timbers, particularly the Oregon and pine, will be subject to delignification if located near the sea. For this reason an inspection on an individual basis is required. Delignification is a breakdown of the cells which results in a substantial furry finish to the outside of the affected timbers. Where delignification is considered minor then it is not a structural issue but mainly visual. In extreme cases, over a prolonged period, this can result in significant structural lose of strength and can cause collapse of a roof.

Shopfront awnings

Many of the shopfront awnings have framework added so that decorative metal or flat sheet fibro can be added to cover the structural framework. Usually the structural framework, particularly in older buildings, is not galvanised and therefore prone to rust. Inspections for the condition is limited, but concern would exist when substantial rust is evident to the perimeter structural beam and soffit cladding.

Where rusting of surface patch overlinings exist, then it would be reasonable that the structural soundness of the framework would be in doubt.

Balconies

Many unit buildings constructed prior to 1985 had insufficient “cover” or thickness of concrete over the structural steel reinforcing within a concrete slab. This allowed salt laden air to penetrate the concrete and cause spalling to many buildings, particularly balconies. If left untreated, balcony failure can occur.