Primary imperative

Take a walk through the village of Toll Bar near Doncaster and you will be struck by the number of contractors’ vans that cram the streets. It’s well over a year since floods swept through the area, destroying hundreds of homes and forcing many families into temporary accommodation, but still the repair work continues.

As water levels rose at the height of the flood, the village primary school was particularly badly affected. Interior partition walls collapsed, electrical systems malfunctioned and, most significantly, its hardwood timber floors expanded and warped beyond repair. The children were decamped to a series of temporary modular buildings, erected on what was once a playing field.

With the community in disarray it became a major concern to get school repairs under way to restore some stability to the childrens’ heavily disrupted lives. ‘It was a heck of a lot of hard work,’ recalls Doncaster Metropolitan Borough Council project manager Karl Kovac, who’s been in charge of the refurbishment operation and is also the scheme’s architect. ‘Once the building was stripped out it looked like a bomb site, the structure was right down to its bare bones.’

The solid Victorian red brick building had not been designed to cope with flooding.

It is also located in a dip in the land, which extended the period of flooding to almost 10 days. ‘At its highest point the water reached about two metres up the walls, which is a lot considering that the school is raised up on steps. It settled down to about 500mm and stayed there for a week or so,’ says Kovac.

The result was serious damage to the timber partitions separating the classrooms from the main corridors. All the floors were affected. Many timber floors had a deep 4ft undercroft – an underfloor void – which had filled with water. All the wall finishes and plastering were also damaged and even areas of tiled masonry had failed to hold back the water, which seeped into the walls.

After the water had subsided, and prior to main refurbishments, all the carpets and furniture were stripped out, along with timber doors and partitions. ‘We knew it was going to take a long time to dry the building, so we tried to assist that by hacking the plaster off the walls up to 1,400mm above ground level. All fixtures and fittings up to this level were stripped back and cleaned,’ says Kovac. ‘There were some lovely hardwood floors in the building, which had concertinaed up and were completely wrecked by moisture. We took those out as well as the floor joists.’

The building was left for a few months to dry using conventional heating and ventilation, but as moisture readings remained high, in April 2008 an efficient dehumidifying machine was brought in to pump super-heated dry air throughout the building and then suck it back in to remove all moisture.

Now bone dry, the building was handed over to main contractor Strategic Team Group (STG). ‘Working on such a high-profile job with the media following your progress puts a little more pressure on to meet deadlines,’ confessed STG contract manager Jason Green. ‘But we’ve had experience doing flood repair work on about 15 domestic properties in Hull, so we knew what we were up against.’

It was a terrible thing to happen but the school has ended up looking 100% better than before

Karl Kovac, Doncaster council

STG’s £409,000 contract encompassed both the primary and adjacent nursery school and required the reinstatement of floors, replacing wall plates on the underfloor sleeper walls, replacing joists, insulating floors, installing a new heating system, electrical upgrades and alterations – but not a complete rewire – plastering, second-fix joinery, installing new doors, frames, architraves, new skirting boards, decorations and suspended ceilings.

The flooring installation took three weeks. First the sleeper walls (intermediate walls in the undercroft cavities used to support timber joists), either damaged by the strip out team, or decayed with age, were repaired. A new 100mm × 75mm timber wall plate was placed on top of each, over a damp-proof course (DPC). Next, 175mm × 50mm C24 stress-graded deck joists were laid at 400mm centres.

A DPC was then wrapped around the ends of the joists where they were pocketed into the walls. The joists were then levelled, with noggins inserted to prevent twisting and to make the structure rigid.

In between the joists, STG placed 100mm-thick Kingspan insulation, capped by the Arnold Laver-supplied, 22mm-thick tongue and groove WBP plywood floor. This comes in 2.4m × 0.6m sheets and was fixed with 65mm galvanised nails. Floor finishes varied from room to room: in the wet areas a Polysafe standard non-slip vinyl was used; main corridors were covered with Rawson Spikemaster carpet tiles; the classrooms got Rawson Felkirk carpet tiles; and the nursery school had Gradus Explorer and Rawson Starquest carpets fitted.

As Kovac explains, many of the materials used at the school were specified to help mitigate the effects of a possible future flood: ‘I chose a plywood rather than a hardwood floor finish to limit future damage. I would have loved to have filled in the undercrofts to make the floors solid, but the void was about 1,100mm deep and would have cost too much to fill.’

Elsewhere, solid masonry walls were erected in place of timber stud walls and the plastering specification was upgraded to cement-based Limelight renovating plaster.

In terms of long-term flood defence for the area, the Environment Agency is investing £2.6m on defences in Doncaster this financial year, with work being carried out at Bentley Ings and the Ea Beck (the combined flows of The Skell river and Hampole Dike). The EA is also working on a full flood risk assessment for the River Don and its catchment area.

That’s good news for Green, whose team won’t be relishing the thought of another job like this one, which meant many late nights and weekends to meet the June completion date. ‘The original 11-week programme had to be extended to 12 weeks due to problems with heating plant and a few issues because of the lead time on certain materials, but the teachers can now get back in ready for start of term in September,’ says Green.

It has been a struggle, but client Kovak is pleased with the results: ‘It was a terrible thing to happen but the school has ended up looking 100% better than it was before. To come from the bare bones starting point to where we are today is brilliant, it’s a big achievement.’ cm