Floor slab dropping in Co. Kilkenny

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In modern construction, most if not all internal walls are constructed on traditional strip foundations. Along with other functions, these walls provide support to the roof if it is of traditional ’cut’ construction. One key difference between a ‘cut’ roof and a ‘trussed’ roof is that the trussed roof transfers its load to the external walls only and does not need intermediate support, unlike cut roofs.

In some bungalows with trussed roofs built in the last century, the internal walls were built on the floor slab and constructed in masonry or timber stud. As very little load was applied to these walls, the theory was that strip foundations were not required. This approach has been completed in both one off and estate housing. However, this type of construction requires very good ground conditions and a high standard of construction in order for the floors to perform over the buildings intended design life.

The tell-tale signs for floor settlement in dwellings with trussed roof construction are normally represented by horizontal cracking or gaps at the junction of the internal walls and the ceiling. And this is certainly the case at this property in Co. Kilkenny where there is moderate cracking throughout the property at this particular location. An internal trial hole revealed that the floor was constructed on made up ground full of broken tiles and broken concrete, clearly unsuitable for any type of floor construction.