Minto & Turner Building waterproofing
Grade II listed building
Requirement to provide totally dry space while preserving historic features including 1867 baling press
The mill above is being converted to apartments, so a structural warranty provider is on board, meaning that their requirements/approvals for waterproofing design and installation are a requirement
The structure suffered issues of water ingress associated with the adjoining canal lock, but could not be 'tanked' (listed) and we provided a creative solution
Four sump pump systems with eight pumps, eight discharge pipes and eight 60kg batteries (for power outage) were installed.
Original brick features retained in areas.
This was an unusual case in that 50% of the basement included a suspended timber floor, i.e. floorboards spanning between sleeper walls, with nothing but earth beneath.
This provides no actual floor structure to waterproof, and so a strategy for waterproofing was devised which included removal of the decayed timber and replacement with a concrete slab, bearing onto the sleeper walls with fill material beneath.
In listed buildings, systems must be sympathetic to what is a historic asset. Therefore, you cannot slap cementitious waterproof renders (for example) onto the inside of the structure, because it would bond to it, and this is considered irreversible damage.
As a result, reversible cavity drainage (cavity membrane, drainage channels, sump pump systems) waterproofing is the prefered option.
Type C - Cavity Drainage Waterproofing
Cavity drainage waterproofing is water management, you collect and remove penetrating water while isolating it from the interior so that it does not present an issue. There is reliance on the shell of the building to provide resistance to ingress, so that the cavity drainage system can deal with the volumes of water. If volumes of ingress are high, structures will often receive barrier tanking measures to reduce their permeability, but what do you do if it’s listed and you cannot use tanking to reduce substantial ingress?
This is what we had to design for here.
Part of the solution was to manage groundwater using land drainage. We observed the natural flow of water ingress prior to the concrete slab being laid. Part of the site externally falls away from the building (ground level reduces), and water ingress flowing along inside the building, drained out again local to where the external levels reduce.