Tuesday, 23 October 2012

Transfusion and Diffusion Damp Proof Course Systems

Peter Cox have been successfully installing remedial damp proof courses in buildings of all types since 1951. At that time Mr Peter Cox ran a stone restoration company based in London. He had noted that stonework at the base of buildings was often eroded as a result of rising dampness and he devised a method of retrospectively introducing a damp proof course (dpc) without significantly disturbing the wall structure. The newly installed dpc prevented further damage to the existing stonework and protected any new replacement stone at the base of the building. His original method of installing a dpc was known as the Transfusion system; this was patented, gained Agrément certification and has been listed as a valid method in BS6576 since the publication of the standard.

In brief, a silicon based water repellent liquid is introduced into the base of the walls via drilled holes which are normally into the mortar joint. The siliconate absorbs or ‘transfuses’ into the capillaries of the masonry; this lines the capillaries with a hygrophobic layer which resists capillary attraction therefore controlling rising dampness. The silicone material does not block the capillaries; the masonry can still ‘breathe’ and the wall structure remains fundamentally unchanged. The silicon water repellent used in the transfusion system is water based and non toxic; it is completely inert once cured and has no deleterious effect on the masonry into which it has been introduced .

Due to the installation process generally being via drilled holes in the mortar joint there is minimal disturbance of the actual stone or brickwork and once installed the holes can be re-pointed with negligible aesthetic impact.

Images showing installation of transfusion system and diagrammatic illustration of principle.

The transfusion system has been employed in thousands of prestigious and historic listed buildings throughout the UK and in other parts of Europe including Venice and Gibralter. Well known examples in the UK include York Minster, Selby Abbey, The Royal Mint, The Bishops Palace of Lincoln, Burleigh House Estate and Normanton Church.

Transfusion being used in a thick stone column of a university building.

Normanton Church – this ancient church was within the flood area of the proposed Rutland Water Reservoir. Prior to filling the reservoir the ground level outside the church and the floor level inside was raised by approximately two metres. A damp proof course was installed by transfusion above the new level to protect the stone walls from rising dampness in what were to become fairly extreme conditions.

Normanton Church after completion of the reservoir – the church is now used for exhibitions etc.

In 2002 Peter Cox developed the Diffusion system which was a natural progression from Transfusion. It is installed in a similar manner, the essential difference being that the silicon based water repellent material is now in a thixotropic cream form rather than a liquid. This allows greater control of the installation. Installation is via 10 -12mm diameter holes, which again, when drilled into the mortar joints enables a dpc to be installed with minimal disturbance and visual impact on the building, making it ideally suited to historic buildings. The water repellent material has no deleterious effect on the masonry. Installation of a dpc in this way prevents rising dampness and once dried down, damage to internal decorations is prevented and further damage externally from freeze/thaw is controlled.

Diffusion dpc installation.