Raised access flooring offers flexibility, but poor specification, overlooked expansion gaps and cost-cutting decisions can quickly turn adaptable office space into a visibly failing floor, says Richard Renouf
RAISED access flooring (RAF) usually comprises wood-based panels overlaid on the top and sides with metal. These are installed on columns to create a floor with a void underneath to allow for power and comms cables to be run to any part of the floor and, in theory at least, changed at will. This can be very appealing to a client but can cause some poor decisions to be made when flooring is being specified.
A flooring contractor wants – needs – a suitable surface for the flooring and, no matter how well RAF panels are fitted, the joint lines will invariably show through LVT and, in some less-well installed cases, will show through carpet tiles, so it’s advisable to prepare the RAF surface using a plywood overlay or a suitable smoothing compound. This, however, can cause the client to assume that this would prevent the panels from being lifted easily if the cables ever needed to be moved around.
This was the case with a recent inspection where an additional constraint was cost. The client pared the specification back to the absolute minimum and, of course, complained when the flooring failed to perform well.
The property managers who had been responsible for fitting out the offices asked me to take a look and advise them about a specific problem. We started on the sixth floor and as soon as we walked out of the lift lobby, the state of the flooring was very poor.
The LVT tiles showed every joint line in the uneven RAF panels. This was not the issue I had come to see, and I was asked to ignore it as the client had not complained about this.
They took me towards the windows. It was a modern office building with full height windows on all four sides and along the floor level frames the flooring was lifting and buckling. Where the flooring was LVT this was severe and where it was carpet tiles it showed as a single line, one tile back, where the tiles were peaking along the joint lines parallel to the frames.
‘It’s solar gain causing the building to expand, and the flooring contractor doesn’t want to know’ they said. ‘But we’ve never had any problem with expansion of RAF panels, so we need to understand what’s going on.’
The flooring had been laid on a tackifier which had been applied over the entire floor area. Some remedial work had been done to try to get the tiles to lay flat using double-sided tape, but this had caused the adjacent tiles to ruck up instead. As we walked the floors I noted rucking in other areas, especially where the flooring met structural features such as pillars.
One floor had not been leased and so had been left with just the RAF panels exposed. These were very uneven and it was obvious that whoever had needed to lift any panels did not have the right tools and so had levered them up along the edges causing the metal to buckle. This would need more surface preparation than ever when it was time for flooring to be laid. But I looked at some other details. Around the entire perimeter where the RAF panels met the walls, and wherever the panels came up to a structural element of the building, there was an expansion joint between the panels and the structure. It was only about 5 mm thick, but it was necessary because the floor would expand and contract at a different rate to the building.
The flooring contractors had not taken this movement into account and had close-fitted the tiles against the walls and window frames. Although the amount of expansion was minimal – millimetres over floor areas of 30 metres and more – it only takes a tiny amount of tightness to cause significant rippling. Of course, solar gain played a part, but more to do with softening the tackifier and breaking its grip.
British Standards require that any expansion joints in a subfloor are continued up to the flooring surface although exceptions can be made when the flooring is floating and the subfloor is free to move. This is easy to remember when the expansion joints are between sections of a concrete slab or between sections of a building because they are visible. In this case the joints looked more like a finishing trim for the RAF panels and I could understand how they were missed during the laying of the flooring, but was surprised they were not considered when problems started to arise.
The RAF panels had not been uplifted or swapped around since the building had been occupied and in my opinion the additional ‘hassle’ of lifting and replacing panels – if it ever became necessary – was more than worth the very poor appearance of the installation because no interlayment had been used. But they tell me the customer is always right and at least this had not been part of the complaint.
Richard Renouf is an independent flooring consultant