St Thomas


Platon membranes go above ground to waterproof ancient priory conversion

Isola Platon membranes, together with other Triton waterproofing and timber preservation systems, have been used in the refurbishment of ancient priory outbuildings on a site classified as a Scheduled Ancient Monument. St. Thomas’ Priory, whose origins date back to 1174, is a unique conversion development of five sensitively restored barn conversions alongside a selection of high quality, stylish new builds.

Local developers contracted Rudders & Paynes to install a Platon cavity drain membrane system to the walls and floors of each barn conversion. Normally installed to provide below ground structural waterproofing, the Platon membranes were specified as an alternative to traditional chemical injection damp proofing systems because building regulations prohibited the drilling into any of the original stone walls. For the same reason the membranes were fixed using ‘Cobb plugs’, which are inserted into mortar joints, instead of the usual brick plugs.

  • The sensitively restored St Thomas Priory outbuildings
    The sensitively restored St Thomas Priory outbuildings
  • Original details have been retained in the development
    Original details have been retained in the development
  • Platon membranes installed to internal walls and floors
    Platon membranes installed to internal walls and floors
  • Cobb plugs were used to fasten the membrane in place of normal brick plugs
    Cobb plugs were used to fasten the membrane in place of normal brick plugs

Rudders & Paynes’ General Manager, Tim Langham, said, “This was the first time we have installed Platon membranes in an above ground situation. But it was imperative to provide some sort of damp proofing system as some floors and walls are partly below ground level.”

To meet building regulations, the Rudders & Paynes team first applied a layer of Triton TT Super to the surface of each new floor slab. Part of Triton’s new range of concrete waterproofing products, Triton TT Super is a surface applied system which waterproofs and protects concrete in depth. It is supplied as a powder which is mixed with water and typically applied on concrete structures such as basements, retaining walls, concrete slabs and water retaining structures such as reservoirs, tanks and swimming pools. The chemical composition works to prevent water ingress, even under pressure, but allows the passage of water vapour so the concrete continues to ‘breathe’.

In one of the Priory buildings, where only one end wall was below ground level, the floor of each unit had been laid to a fall, and Triton Aqua Channel perimeter drainage was installed along the front edge of the slabs to collect any water from behind or under the membranes and direct it to a suitable drainage point. In other units where all walls and floors were below ground level, the Triton Aqua Channel was fitted to the entire perimeter. The cavity membrane system, comprising Platon Multi to the walls and deeper studded Platon P20 to the floors, was then installed using Platon Corner Strip to seal the wall/floor junction. Platon Multi and Platon P20 combine to form a BBA certified system commonly installed as a method of below ground structural waterproofing. A key benefit of cavity drain membranes (particularly when compared to cementitious tanking systems) is that there is little or no preparation required to the substrate. This is particularly important when the building is of historic interest as the original fabric of the building can remain unaltered. At the St. Thomas’ Priory site, following the installation of the Platon cavity membrane system, the walls were dry lined and insulated and a concrete screed applied to the floors.

Additionally, all roof timbers were exposed and cleaned by the developers who also carried out traditional repairs as required to the original beam ends. Rudders and Paynes then treated all timbers to prevent any further fungal or insecticidal infestation, using Triton’s Tritech 120 Plus, a modern, water based, dual purpose preservative with a one hour HSE re-entry classification.

Rudders & Paynes originated in the 1800’s but has operated as a remedial contractor since 1956. Based in Worcester and Solihull, the company works throughout the West Midlands specialising in timber and dry rot treatments, damp proofing and associated repair works.