Why are there two different methods of fixing roofing slates? And how do you decide which is the right option for your job?
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Here are the facts you need to fix the perfect roof every time.
Historically, roofing slates were fixed with wooden pegs, a practice that evolved into two radically different methods: in the UK the pegs were replaced by nails; on the continent they were replaced by S-shaped metal hooks or ‘tingles’.
Designing a successful slate roof must take into consideration a number of related factors and this includes the method of fixing to be used. The site’s exposure level, the roof’s pitch, the type and size of the slate being used and the roof’s shape and aesthetics all play a part in determining which method of fixing will be the most appropriate for the design.
As the two methods have advantages and disadvantages that influence the design and affect the roof’s success, it’s important to be aware of them.
Hook fixing offers greater resistance to wind lift as the hook secures the tail of the slate and locks them together more securely. As a result, this method is commonly used in those parts of the UK where the site’s exposure level is considered ‘severe’, e.g. Devon and Cornwall, Wales, Cumbria and Scotland.
The design of the roof influences the shape and size of the slates to be used and successfully incorporating some features, such as curves, swept valleys, cones and domes, relies on being able to use narrow slates.
Slates to be fixed by nail need a 25mm margin between the hole and the longitudinal edge and this restricts their width to a minimum of 150mm. However hook fixing allows slates with a width of just 100mm to be used.
Where hook fixing is used, the end of the hooks are visible. Where nail fixing is used however, the nails are covered by the overlap of successive rows, which gives the roof a smooth appearance.
One thing to consider when using nail fixing is that with the nail and its hole covered by the next row of slates, replacing individual slates fixed with nails can only be achieved using hooks.
Slates to be nail fixed can be supplied either pre-holed at the quarry or unholed for holing on site, a task that increases labour costs and wastage. Slates for hook fixing are, of course, supplied unholed.
Nail vs Hook fixing: A quick comparison
|Hook Fixing||Nail Fixing|
|Resistance to wind lift||Good||Okay|
|Resistant to storm force winds||Yes||No|
|Allows roof pitches below 20 degrees||Yes||No|
|Effective width of the slate is reduced||No||Yes|
|Allows the use of narrow slates||Yes||No|
|Aesthetic appearance||Tips show||Smooth|
|Holing on site – labour cost||Not needed||Yes|
|Holing on site – material cost (wastage)||None||Possible|
|Lifespan of the fixing is the same as the slate||Yes||Yes|
|Risk of ‘nail sickness’||None||Possible|
|Reduces wastage on site||Yes||No|
|Allows use of smaller slates||Yes||No|
|Slate retention if it breaks across its width||Yes||No|
|Ease of maintenance and slate replacement||Easy||Difficult|