Working from the ground up
The Tannery Building in Glasgow’s St Andrews Square is an iconic five storey end terrace, built in an Italianate style in 1876-77 for John Inglis and Co. by an unknown architect. It has been converted to residential and commercial use and is a listed category B building – of regional importance.
The Peter Cox Glasgow team carried out below ground waterproofing on both ground floor commercial properties as Branch Manager Gary Bouse explains: “The client invited us to inspect the property where free-standing water and severe condensation had been reported. Upon inspection and given the sit conditions and history we advised that the full British Standard waterproofing to basement recommendation BS 8102 1990 revised 2009 was implemented.”
Peter Cox: A Controlling factor
Peter Cox Ltd had to ensure control of water entry and recommended the installation of a Cavity Drained Membrane System to specific areas. This incorporated perimeter drainage and the formation of a sloping soffit to he metal decked area and was combined with a Sika barrier system.
Gary said: “The British Standard identifies that a drained cavity system is the safest method available for maximum assurance against system failure. This is because ground water is controlled, diverted and harmlessly removed rather than being ‘’blocked’’ at the point of entry. Consequently the risk of increased hydrostatic pressure is reduced and cavity drained membranes require little and sometimes no preparation.”
The cavity drained system is designed to control both water vapour and the penetration of ground water. Once the system is in place, three main functions are achieved. First the system controls vapours, secondly damp pressure is equalised and finally the system acts as a drained cavity system, controlling water ingress.
Cavity drainage systems work on the principal that any water entering on the “wet” side of the system is either drained away to a sump chamber and pumped to a drainage point or where local conditions allow, by natural drainage. The cavity drained system recommended by Peter Cox Ltd is a sealed system with natural drainage across the existing floor enabling water to collect into a sump chamber where it is pumped to an external drainage point.
Before fitting the system, Peter Cox had to carry out preparatory work including the supply and application of Sika 107 cementitious slurry full height to public area walls and the application of Peter Cox drywall plaster to hard wall areas. In order to install the cavity drainage system the team excavated the sub site to accommodate the installation of the sump chamber.
Gary said: “At this stage we carried out a water flow test to establish falls and low spots and then we removed any hollows with a latex screed and formed the necessary chases. Next, we excavated the existing floor slab to accommodate the installation of ‘aqueduct’ perimeter drainage and then provided and fit submersible double pumps, complete with an alarm system.
“The effectiveness of this system is totally reliant upon the pump discharge and so we always remind clients about additional features to guard against pump/electrical supply failure.”
Once the pump was installed. an 8mm cavity membrane system was fixed to the wall surfaces with a specialist sealed plug. The plug has a dual purpose; fixing the membrane system to the wall surface and allowing studding/battens to be secured when specified, without piercing the installed system where appropriate.
On the ceiling a Delta MS 500 membrane spans the 7No arches of the area. This required a specialist design were the arches met the upstand to the flat soffit ceiling. This combined with cast iron supports, which again required a special detail to tie them from the arches and down below the floor membrane.
Peter Cox Ltd provided a 20mm floor membrane which provides greater drainage capacity and helps prevent silt or lime build up blockages which can occur with smaller size studs. A further water flow test was carried out through the jetting eyes of the system to ensure a flow of water from the slightly higher floor level of the east basement to the sump pump assembly in the west basement.
A new lease of life
Gary adds: “The owner and occupiers of this property can be assured that the basement is now fully waterproofed and dry and will remain so for many years.
“The property has been revisited to ensure that all problems have been controlled and the result has been a magnificent success, with the client now letting previously unusable areas, that their client’s have stated they will use as part of their business.”