Subfloor preparation products from Bostik have been used in the redevelopment of St Ann’s Hospital in Tottenham.
The scheme, which included the creation of a 74-bed mental health facility, was highly complex as the unit’s three blocks each had different requirements that needed addressing in different ways – for example some parts of the subfloor were made of concrete while others were made of plywood. Bedford-based flooring contractor, Blade Flooring, was appointed to install the floor coverings and worked with manufacturer, Bostik, to choose the right products. For the concrete areas, HYTEC E570 ONE COAT damp-proof membrane (DPM) was specified to suppress the residual moisture in the subfloor, followed by GRIP A526 UNIVERSAL PRIMER and SCREEDMASTER SL C540 FLOW smoothing compound, which provides improved workability and superior flow characteristics. For the plywood areas, once they had been primed, Bostik specified SCREEDMASTER SL C530 FLEX, a fibre-reinforced, heavy-duty smoothing compound particularly suited for application onto wooden floors.
This varied approach continued into Blocks G and H where, again, some parts of the subfloor were concrete and others were plywood. In this case, however, there were a number of hydration cracks in the surface of the concrete and these were overcome with Bostik RENO P520 EASY, a crack repair system including a solvent-free, 2K repair resin and stitching pins, which can be mixed easily within its containers and dries in 30 minutes. Once the cracks had been filled in, the team primed the surface with GRIP A936 XPRESS, Bostik’s water-based primer with high grip and a fast drying time, before smoothing it with SCREEDMASTER SL C530 FLEX. And Block B required yet another approach, as there was Lytag screed present in parts of the subfloor. In some areas, this could be worked around, while in others it was so damaged it needed to be removed.
In the areas where a new screed was required, Bostik advised Blade Flooring to apply a slurry mix of TECHNIS C720 FLOW – a pre-blended, rapid fluid screed, mixed with Bostik SBRa co-polymer latex that toughens, waterproofs, and improves the chemical and abrasion resistance of screeds. Once the slurry mix was applied to the prepared substrate, TECHNIS C720 FLOW was again used to reinstate the levels where the Lytag screed had been removed. Once applied, TECHNIS C720 FLOW can receive moisture - sensitive floor coverings in as little as seven days. The team then primed the surface with GRIP A936 XPRESS, before a layer of SCREEDMASTER SL C540 FLOW was applied to smooth the subfloor ready for the adhesive and floor coverings. Ian Dennis, technical specification manager at Bostik, said: “This was a large project that involved modernising a sprawling 1950s hospital. “It was therefore necessary to advise Blade Flooring on a range of different subfloors, which were in various states of disrepair and had a number of requirements.
GETTING THE JOB DONE
“With a project like this, you don’t know what you’re going to find until you lift the flooring, and in this case, there was everything from Lytag screed to old pipework. “However, once our team had inspected the site, we presented a set of recommendations for how to prepare the subfloors and this enabled them to get the job done.”