Flood resilience showcased in Carlisle

Part of the Cumbria Flood Resilience Showcase, the project was the brain-child of Mary Donhau, a flood resilience expert and campaigner. “It came on the back of the Peter Bonfield review that followed Storm Desmond,” explains Mary, who has been awarded an OBE for her services to flooding protection and recovery. “The idea was to find a couple of properties which we could make resilient, and to make the information available to as many people as possible.” Botcherby was the first of the showcase projects.

Although the Cumbria project refers to resilience, terms more commonly being deployed now are: ‘water-exclusion strategy’ (i.e. resistance), and ‘water-entry strategy’ (i.e. resilience).

A ‘water-exclusion strategy’ house is built so that water cannot get into the building and cause damage. A ‘water-entry strategy’’ means constructing the house so that although water may enter, the impact is lessened, structural integrity is maintained and drying, and cleaning is made easier.

The likely depth of flooding will impact on the chosen design. For low water depths, a ‘water-exclusion strategy’ typically is recommended. A ‘water-entry strategy’ is needed for higher water levels: a difference in water level of over 0.6m between inside and outside can cause significant structural damage to standard masonry buildings.

In practice, a pragmatic combination of both is taken because it is often either prohibitively expensive or impractical to provide a completely flood-resistant building – especially in cases where flood protection is being retrofitted to existing buildings.

In this context, Safeguard Europe – a UK-leading specialist in damp-proofing and waterproofing technology – was one of several companies to invest in the Cumbria Flood Resilience Showcase in Botcherby, a suburb of Carlisle. Other funding came from the Environment Agency and the North West Regional Flood and Coastal Committee. Safeguard provided a raft of external and internal products which specialist contractor RTC Group installed, donating its time and expertise to the project too.

Externally, RTC applied Stormdry Masonry Protection cream to the brickwork, having first repointed any cracks or gaps using mortar containing Stormdry Repointing Additive. “The purpose of the masonry protection cream is to stop the water getting into the brickwork and to aid drying out afterwards,” explains Clementine Walker, Research Development Laboratory Manager at Safeguard. Unlike some ostensibly similar products, both the masonry protection cream and the mortar additive allow the walls to breathe.

Internally, RTC replaced timber studding with blockwork up to a height of 1.2m and used Vandex Uni-Mortar 1 Joint Fill Compound to fill the gap between the floor and wall, one of the most common paths for water ingress during flooding. The contractor then applied two coats of Drybase Liquid Applied Damp Proof membrane to
the floor.

On the internal face of the kitchen’s external walls, RTC installed Dryzone damp-resistant plaster. On the ‘internal internal’ walls, RTC used Safeguard’s express system: moisture-resistant plasterboard fixed with Dryzone Drygrip waterproof adhesive. All walls were skimmed with Dryzone Hi-Lime finishing plaster.

Both Dryzone damp-resistant plaster and Dryzone Hi-Lime finishing plaster have been designed to prevent salt migration, and both are porous to aid evaporation. This means they can be left in-situ to dry out should flooding occur again.

These breathable, moisture-resistant plasters allow the fabric of a flooded building to dry out whilst providing a durable finish that will be resilient to future flooding. Moisture-resistant screeds have also been developed using similar technology.

After a flood, one can – for all practical purposes – simply hose down and sterilise the wall. The make-up of these plasters means they have large pores and a high pore volume. This allows salts to form within the plaster rather than on the surface; and the high pore volume results in high water vapour diffusion (breathability) and higher thermal resistance, reducing the risk of condensation.

In Botcherby, with additional flood resilience measures such as specialist doors and windows, self-closing air bricks and non-return valves, the kitchen – and the whole community centre – is back in use once again. As for disseminating the information and lessons from the case studies, Mary has created a series of videos which are now available on YouTube, alerting people to them via an e-mag, Twitter and other social media.