Was the Fallen Plaster Ceiling Damaged by Water?

Posted by in Case Studies, Ceilings | July 27, 2020

We were informed that a portion of a plaster ceiling had fallen (featured photograph).

The question was, “Was it related to a previous water incident?”

The account of the water incident indicated that it occurred on the floor directly above the area of damage.  We were told that a radiator from the hot water heating system had sprung a leak that was not discovered immediately.

The floor joists exposed by the fallen ceiling exhibited water stains (Figure 1).  The nails that remained for the plaster board exhibited corrosion (Figure 2). 

moisture staining on joists
Figure 1 Moisture staining on floor joists.
Nails for plaster board exhibit heavy corrosion
Figure 2 Nails for plaster board exhibit heavy corrosion.

Measurement of the nail spacing for the plaster board disclosed that the nailing pattern met or exceeded the pattern required by historical industry standards (Figure 3). 

Bottom of floor joists exhibit many nails and/or nail holes
Figure 3 Bottom of floor joists exhibit many nails and/or nail holes

The coincidence of the damage with the leakage, the moisture staining on the floor joists, the corrosion on the nails, and the adequate nailing of the plaster board indicated that the loosening and falling of the plaster ceiling was related to the water event that had occurred years earlier.

It is probable that the nails were loosened by the swelling of the floor joists during wetting and subsequent shrinkage of the wood floor joists during drying in combination with the damage to the gypsum plaster board at the nails.  The loosening of the nails and the weakening of the gypsum plaster board loosened the ceiling as the nails withdrew and/or pulled through the board one at a time until enough had loosened to allow the ceiling to fall.  

As Sgt. Preston would say to Yukon King, “This case is closed.”

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