Page 27 - Parquet International december 2014

1) whenever anyone walked over them, some areas of the screed gave off a dry thump and flexed downward (relatively large areas of screed were moving up and down);
2) noticeable differences in level were also ob- servable in these areas;
3) the surfaces of the screed were fairly “brit- tle”; in other words, the cement mix was not compact, and so crumbly that it was imme- diately evident;
4) noticeable cracks had formed near the thresholds of the doors, in particular.
The Project’s General Specifications includ- ed the laying of a sol- id wood floor by glu- ing in every part to be completed on site.
The scruples of the conscientious parquet installer As luck would have it, the parquet installer assigned to laying the floor was suspicious of these anomalies, even if the main con- tractor urged him to meet the deadline nonetheless. In order to get a better idea of its characteristics, I ex- amined the technical data sheet of the rapid hardening self-level- ing screed used. At the start of my technical inspection, I had tried to take a few samples of the screed without success due to the compactness of the ce- ment mix, which was, in fact, so brittle that taking samples was impossible.
The causes revealed
Following other in- spections and checks using the test instru- ments required to ob- tain a more complete picture of the laying of a wood floor, the main
and the contributing causes responsible for the various anomalies observed were iden- tified as:
1. “Screed areas that give off a dry thump
and flex downward when walked on”
This situation that was observed in all the rooms, especially in the areas near walls, can be ascribed to an “accidental” penetration of liquid cement mix beneath the heating pan- R