ALERT | Pyrite & Ground Floor Construction?
There is a lot of uncertainty among Certifiers about the possible consequences of issuing certificates for pyrite and other defective building materials. Recent outbreaks, several years after we thought the problem had been solved, are reported here (see links below for housing in Drogheda and Dublin Zoo).
Inevitably the day will come when an SI9 Certifier has to defend a new pyrite claim. The scale of the problem might be big enough that the Professional Indemnity (PI) insurers decide to defend the case (see the €64,000 Question) rather than settling quickly and paying out from the policy excess.
As a Design or Assigned Certifier you might think that contaminated building material is not your responsibility (see link below). But what about the basic ground floor construction?
In submissions to the Pyrite Panel two years ago both the CCMA (City & County Managers Association) and Consulting Engineers Sutton Cronin raised concerns about the ground floor construction of houses affected by pyrite. They explain-
“If a house is built correctly and the floor slab is exposed swelling of the stone infill beneath then the slab will move upwards in isolation to walls of the building which are not attached to the floor slab. This will result in a clear visible step in the floor slab at all doors. This is clear evidence that the infill is swelling as the slab is lifting. This is NOT happening in the majority of cases reported.
A simple mathematical equation will show that if a floor slab is tied to an internal block rising wall and if the seasonal movement is a mere 1.5mm then a crack of 5mm will result over the door contained in this wall. This is a detail problem and not pyritic heave in the infill”
The County and City Manager’s Association (CCMA) make a recommendation:
“Consideration should be given to reviewing ground floor construction in areas of the country where aggregates that could potential have pyrite, particularly limestone aggregates. The use of suspended floors with walls and roof acting independently is the recommended design for such areas in Canada. In built-up areas such as London, an expandable lining is introduced to mitigate against movement due to vegetation / roots. In sectors most affected by problems of swelling, it has become common for buyers to make and to offer purchase, conditional on analysis of the backfill under the slab”
Are the CCMA and the engineering report suggesting effects of pyrite in ground floors can be mitigated by detailing? If this is the case it is surprising that neither the Department of the Environment Building Standards or the Professional bodies or the CIF have issued any warnings to industry.
Perhaps readers of the blog can point us to any advice issued by the professional bodies to their members about this?
Other posts mentioned in the above post: