A Hole Days Work

close up of home made stave

A recent investigation of a housing development centred on sagging timber joists to the first and second floors. Some problems had clearly been obvious during the construction phase, since some floors had been topped off using a self levelling screed and ceilings had been packed out to make them level. With the properties occupied any survey work had to minimise intrusive access.

In order to check the safety margins the consultants needed to know the deflection each of the joists was undergoing. Levelling on the floor was not an option, due to the use of the screeding, so it was decided to level the undersides of the joists. To minimise the damage small (20mm) holes were bored through the ceiling plasterboard at the ends and mid-span positions of the joists. A special tubular stave was used to access the joists through these holes, the stave being in short secctions so that it could be used over fitted cupboards and other obstructions if necessary.

close range internal levelling

Multiple close up lenses were required for some of the set-ups inside cupboards and showers where focussing down to 750mm was necessary. The illustrations show the small hole required in the ceiling (which was filled and properly repaired by dry-lining afterwards) and a typical set-up using a nest of close up lenses to achieved focus. Continually having to swap around the lenses was a little irritating but it meant that the job could be carried out with only a mnimum of set-ups, thus aiding accuracy.