Surface Regularity Testing

Surface regularity is a deviation in flatness under a straight edge as defined in BS204-1:2003 Annex C which states: 

“Check surface regularity by using a straightedge 2 m long laid in contact with the floor surface and resting under its own weight. Measure the deviations of the floor surface from the underside of the straightedge, between the points which are in contact with the floor surface, using a slip gauge or other suitable, accurate measuring device.” 

Often the test is carried out by simply placing the straight edge on a high spot and the other end supported, thus leveling the straightedge.  Another method is to overhang the straightedge over the greatest identified low spot. 

Both these methods are incorrect. 

The straightedge should be in contact with the slab, resting under its own weight.  The deviation must be measured between two points, which are in contact with the floor surface. To measure the extent of the gap, insert the graduated wedge into the identified gap at 90 degrees to the straightedge until the wedge is in direct contact with both the underside of the straightedge and the top of the surface of the slab, measure from the point of contact between the wedge and the straightedge. 

The testing frequency should be agreed upon by the parties concerned. 

Surface regularity falls into three classes SR1, SR2, & SR3