Building Salt Deterioration

 

The Effects of Salt Deterioration in Buildings

Over the last 10 years, there have been many buildings that have been in the news with either collapsed brick walls, shop front awnings, concrete patios and in part excessively sagged roofs. Many of these are caused by salt deterioration and the affects on a building are of a structural concern, particularly those located close to the sea. Many of our buildings are now approaching the age where the prolonged exposure to salt has now caused significant deterioration to the building. Due to a recent incident at Manly, Council now require that all shop owners in the area provide a Structural Engineer's certification that the shop awnings and brickwork are structurally adequate.

The majority of these problems can be related to salt deterioration of the mortar to the brickwork, particularly in an exposed or part exposed location. This does not preclude that some buildings located 1 to 3 kilometres from the sea can also be affected by salt deterioration over a longer period of time.

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The salt will cause disintegration of the soft lime mortar and can cause some dislodgement of brickwork. The problem is further aggravated by the wall ties which secure external brickwork to the internal skin of brickwork. As the external bricks are wet and affected by salt, this will accelerate the rusting of the ties and can in fact result in the ties being completely rusted through.

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This leaves the external skin of brickwork unrestrained to the building and can be subject to excessive structural bowing. In extreme cases this will result in the wall physically collapsing and can cause death or significant injuries. There are some situations where soft callow bricks are deteriorated due to the salt environment. Further, many of the bricks used during the 1960's, 70's and 80's are not salt tolerant and particularly in exposed locations can be subject to surface disintegration.

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Terracotta roof tiles are not salt tolerant, particularly those constructed after 1950. The degree of deterioration is not evident from the external side but can be readily viewed from the underneath side. In some extreme cases the tiles can be affected by excessive salt deterioration and require replacement within 20 years from the date of installation. Failure to replace the affected tiles will result in excessive water entry to the building.

Many of the structural timbers, particularly to Oregon, can be affected by delignification due to the salt environment. Delignification is a breakdown of the cells of the timber which does result in a substantial varied look to the timbers. The early stages of this is not a problem but in an advanced condition it can cause significant lose of structural strength of timbers and can, in the extreme situation, result in the collapse of the roof.

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If you have any queries in respect of possible salt deterioration problems then please don't hesitate to contact us.

David Hall Building Appraisals.

March 2008 ©