BCAB #1087 - T-Nails for Cedar Shakes
August 29, 1989
Re: T-Nails for Cedar Shakes
With reference to your letter of July 21, 1989 regarding the use of T-nails, under the equivalency provisions of the Code, for installing shakes and shingles.
This issue has risen on previous occasions, the last being dealt with under Appeal #956, a copy of which is enclosed. On a general basis we are unable to depart from the decision given under #956; the new edition of Standard CSA 0118.1 will shortly be adopted without qualification respecting fasteners, and it specifically recommends a minimum crown size of 11 mm for T-nails, whereas those addressed in your letter have a crown size of 6.53 mm. While the recommendation is not mandatory, we must conclude that it was considered to be of sufficient importance to warrant a positive statement from the committee responsible for the standard, which refers only to a minimum crown size for this type of fastener. In fact 11 mm represents an increase from the 9.5 mm crown size recommended in the previous edition of CSA 0118.1.
We appreciate the testing which has been undertaken, but suggest that these results should be of far more value to the appropriate standards committee who we assume are in possession of factual data supporting the necessity for a minimum 11 mm crown. It may be that the particular type and quality of T-nail tested is superior to those envisaged by the standards committee; unfortunately they provided no basis for making such a comparison, and permitting application of the Code equivalency provisions. Under the circumstances we do not feel that a departure from the recommendation in the standard is justified and are unable, at this time, to accept the request for approval. If, however, the 11 mm recommendation is not supportable, then the issue can be reviewed; you may wish to pursue this aspect with the standards writing organization.
With regard to the specific installation which appears to have generated the Appeal, namely the Scott residence on Saltspring Island, we have no real concern; the roof has been inspected by Warnock Hersey, an agency accredited in this field, and the particular T-nails used evaluated in conjunction with shakes from the actual site. Under these circumstances, if the agency involved is prepared to certify that the completed installation provides the same level of weather protection, over the same anticipated life, as the requirements in the Code, we would consider this installation to be acceptable. In such a situation it would be completely pointless to require that the roof be replaced.
J.C. Currie, Chair