Point loadings on insulation boards

We have talked regularly about compliance in this column, and with the publication of the Construction Products Association (CPA) White Paper ‘Proposed construction product competence standard’ the direction of travel for 2023 and beyond is clear- everyone in construction will need to pay more attention to the suitability of a product for a given application.

This is why much more attention is being paid to manufacturers’ published product information by specifiers, roofing system suppliers and trade associations.

A recent topic of discussion within flat roofing trade associations has been the issue of Compressive Creep with insulation over time. Whilst not a high focus topic like fire performance, it is nonetheless an important in-use assessment of an insulation product’s suitability for an application.

Insulation companies publish values for compressive strength related to testing to BS EN 826:2013 Thermal insulating products for building applications. Determination of compression behaviour. However, Compressive Creep, which looks at how insulation performs under longer term loads, is tested to EN 1606:2013 Thermal insulating products for building applications – Determination of compressive creep.

This is an important difference as we all know that many roof surfaces are subjected to permanent distributed or concentrated loads, such as air conditioning units, mechanical plants, water tanks, etc. A green roof and/or blue roof could also be classed as permanent distributed or concentrated loads. As we write this column we are not aware of any PIR or Mineral/Stone Wool insulation boards that declare Compressive Creep values. One BBA Certificate for a commonly used insulation of this type actually states that “The products have not been assessed for use with permanent distributed or concentrated loads, such as air conditioning units, mechanical plants, water tanks, etc. Such loads should be supported directly on the roof construction. The products are not suitable when permanent roof access is required”. Would you pass a competency test if you used this product on a flat roof and placed M&E plant directly on it? The BBA suggests not.

There are flat roof insulation products that provide EN 1606:2013 Compressive Creep test data related to testing from anything from  122 and 608 days. This test data reflects an expected life performance of between 10 and 50 years’ service life. These products are generally inverted roof insulation boards manufactured from XPS and EPS, but FOAMGLAS also provide this data for warm roof insulation boards.

We wish you all a Happy Compliant New Year in which we will continue to seek to assist your understanding of insulation board application.

Next month: When is non-combustible insulation not non-combustible?