BS 8203 guidance helps flooring contractors assess and achieve correct floor flatness, says Richard Renouf
BS 8203 doesn’t actually specify the surface regularity (flatness) that is required for a resilient floorcovering. Instead, it gives details of how to measure flatness and provides three ‘grades’ that can be used to specify how flat the floor needs to be by the main contractor.
The British Standard states that the floor surface level (ie height) should be checked against the datum level using ‘normal surveying methods’. This should ensure the floor height is where it needs to be.
It then goes on to state: ‘Check surface regularity by using a 2m long straight edge laid in contact with the floor surface and resting under its own mass. Measure the deviations of the surface from the underside of the straightedge by means of a slip gauge or other suitably accurate measuring device’.
Most contractors I know check surface regularity using a 2m straight edge and some substitute a 3mm thick disc or packer instead of the slip gauge so they can know quickly whether it’s a ‘pass’ or ‘fail’ against SR 1. But the standard allows for alternative methods to be used, as long as they’re ‘accurate’ (there’s obviously room for debate here!).
This week I was called out to a site where a new wing was being added to a hospital. The main contractor had set out a generous specification for the floor – it only needed to be to SR2 (5mm over 2m). The contract made clear the standard for the screed before it was passed to the flooring contractor, and it was contractually down to the floorlayers to assess the screed surface and apply a dpm and smoothing compound to achieve the correct flatness.
All seemed to be well until the fitting out began. Fortunately this was before any flooring was laid. The door hangers found that when they adjusted the doors to the correct height at the threshold, some of them wouldn’t fully open because they scraped against the smoothing compound.
As the doors were set to an exact 6mm gap at the bottom, and the individual doors were less than a metre wide, the floor was clearly not up to the specification.
I’d hazard a guess that these contractors, like many, assume a smoothing compound is a self-levelling compound. In fact, a smoothing compound may have self-levelling properties, but that doesn’t mean it’ll flow like water and flatten out an entire floor area. There’s a real skill required to ensure the right amount of compound is laid down to each part of the floor area to achieve a high quality finish.
Sometimes floorlayers who aren’t quite up to scratch are nevertheless very creative when it comes to excuses. In this case they met the project manager on site with a 2m level and found a place where it showed no deviation and said that was an accurate enough test.
The PM moved the level to show this wasn’t the case but had limited knowledge of floors and so was unable to persuade the floorlayers this wasn’t satisfactory. This was the reason for my call.
Some years ago I purchased a laser floor scanner which I adjust to the datum level and then it highlights any part of a floor that deviates from this datum. It’s a very quick way to find both level and flatness as a single line separates into two lines, with the gap between them being the height variance from datum at that point.
Sadly this device was discontinued by the manufacturer some years ago but I’m sure some of my readers may have one lurking unused in the back of a warehouse somewhere. If you aren’t going to use it, let me know and I can match you up with someone who would buy it from you.
The scanner showed the story really quickly. The floor surface didn’t even meet SR3 (10mm over 2m) and there were drop-offs along some walkways of more than 25mm, and some localised dips and undulations that would present problems when the sheet vinyl flooring was laid.
The project manager was as amused as me when the site manager picked up the scanner and started testing the floor levels throughout the building. ‘Let me just check this…and this…and this…’!
Fortunately I’d allowed plenty of time for my inspection and it was clearly helpful for him to have a better understanding of the situation.
I left after giving the assurance my report would be done as quickly as possible, but the problem became a crisis within half-an-hour of me being on the train back home. I received a call from the PM telling me that when he’d reported back to the main contractor he was told to stop all the flooring work with immediate effect. As a result I arranged the following day to return once my booked appointments were finished to demonstrate the issue to the manager of the flooring contractors.
We also discussed what could be done to ensure a better surface regularity on the areas about to be dealt with, and how a cross-line laser to good effect to check as the smoothing compound was being pumped across the floor, as a 2m straight edge would be no use on a wet compound.
The detail of the British Standard states that ‘the number of measures required to check the levels and surface regularity should be agreed between the parties concerned, bearing in mind the accuracy required and the likely time and cost involved’. Any saving in these costs had already been wiped out by my fees for the two site visits and the report.
Surface regularity isn’t a linear measure, even though it’s measured in a straight line. The bottom edge of a door is straight, but it swings across an arc that needs to be flat, and other features such as wall-panelling, dividers and desks will highlight imperfections, too.
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Richard Renouf is an independent flooring consultant