By Ian Weakford, Sales & Marketing Director @ Hambleside Danelaw
With the increasing unpredictability of British weather, particularly in winter, ensure you- and the properties you manage- stay dry.
Extreme winters have challenged roofing product manufacturers to develop solutions to reduce the impact of the weather, particularly wind. It causes slates and tiles to dislodge, underlays to vibrate, and can lead to rain ingress. Even winds as “low’ as 20mph can cause damage.
In most situations there is therefore a requirement to use dry, rather than ‘wet’, fix solutions, so that the roof details, particularly ridges and hips, remain intact, and therefore weatherproof, regardless of the extremes of winter weather. Because the fixing method is dry, remedial work can be carried out almost regardless of the weather; ‘wet’ methods, such as mortar, by contrast need a degree of decent weather for the mortar to cure before being subjected to load.
The realisation of the practicality and durability of dry fix solutions has seen a growth in their popularity. This in turn has led to a growth in the number of mechanically-fixed products available, with a corresponding diversity of quality and performance. It is a case of ‘you get what you pay for’: products with a higher unit cost are usually manufactured and tested to higher quality standards, so can be expected to be easier to use, and to perform better. Thus the perceived higher cost can actually result in a saving, in that the product will withstand the loads, remain in place, and reduce repairs. To put it into perspective, storm Doris in 2017 saw a 300% increase in the cost of insurance claims from wind damage.
Inevitably, in line with these market force changes, a British Standard has been introduced. BS8612:2018 Dry Fixed Ridge, Hip and Verge Systems for Slating & Tiling: Specification aims to create minimum performance & durability standards for dry fix products used in these areas.
But making a roof weatherproof has to be balanced alongside allowing the roof to “breathe”, to avoid any interstatial condensation. Debate continues to rage about the best way to achieve this, with the arguments primarily focusing around the underlay. Should it be airtight or permeable? Because it is a topic so debatable, our view is always to follow a ‘belt and braces’ approach: vapour permeable underlay AND ventilation. Current Regulations require the ridge to be mechanically fixed, so the small, additional material cost is more than outweighed by the cost of fixing a roof riddled with damp and rot from condensation.
A roof does need to breathe, so ventilation openings will need to be provided anyway. Some argue that air permeable membranes are more effective in allowing the dissipation of moisture, but their use needs to be considered in the increased tile fixing specification as there will be greater load on the tiles- another reason to rely on mechanical fix rather than ‘wet’ which is so dependant on the quality of the mix, the quality of application and the weather.
As with dry fix products, membranes too vary in quality and price, and again, you get what you pay for. With the recent years of high winds, the UK has now been zoned by wind uplift. Most membranes are not certified for use in all zones, unless particular attention is paid to the fixing method i.e. restraining battens or taped joints.
To be sure your roofs will perform, the best solution is to check your spec. with the manufacturer, and be sure you read the small print, to understand any limitations of use, and to ensure the roofing contractor quotes for and installs what you have specified.