19 September 2016

Mortar has historically been the popular way to install tiles and fittings at a number of key roof areas, including roof hips, ridge and verges, but there a number of factors that cause mortar to fail, making it unsuitable in the long term.

Recent changes to BS 5534 - the code of practice for slating and tiling - have introduced some important changes to the way that roofs are fixed. In particular, mortar is no longer recognised as being suitable for providing a sole means of fixing under BS 5534 - now, any mortar bedding, such as traditionally found on the ridge, hip and verge, must now be accompanied by a mechanical fix.

The benefits of dry fix

The question of whether to use mortar or dry fix really comes down to the issue of future maintenance and cost. Dry fix is typically quicker to install and can be done so in any weather. In the long run, when maintenance is factored in, is always more cost-effective when compared with mortar.

There has long been an increasing move to adopt dry fix across Europe, as building codes are standardised, and dry fix is already the most popular method in the UK and is well on course to become the more popular method in the future. In many cases, dry fix also provides benefits in terms of the ventilation performance - read more here.

The pros and cons of mortar

Although the cost of having ridge and hip tiles secured by mortar may be cheaper in the short term, there are undoubtedly long term maintenance costs. Mortar only has a limited lifespan and is greatly affected by the quality of the mix, building movement and environmental conditions.

Whilst dry fix should always be preferred, there are some instances where it may still be necessary to use mortar - perhaps on properties with a heritage aesthetic. For these circumstances, Marley Eternit provides a range of mechanical fix solutions for any mortar bedding requirement, so that they comply with BS 5534. In addition to providing a mechanical fix, you'll need to ensure that a suitable mortar mix is used. The NHBC has guidelines which state that an acceptable ratio for roofing mortar is 3:1 sharp sand/cement.

Pre-mixed roof mortars are also available that are accepted by the NHBC.

To find out more about the changes to BS 5534 download our guide.


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