Nailing natural slate, how tight should the nails be?

[epsilonGreedy]

When nailing new natural slates how tight should the slates be nailed to a batten?

 

I understand the nailing should not induce any bend to the slate which defines the upper boundary to my question. So maybe the question is how loose is acceptable?

 

I am nailing with copper nails on 2x1 battens with the rafters below at 300mm centres. The slates are 20x10 of average thickness (guess 4mm to 5mm thick). It is a 30 degree roof which might be more prone to wind uplift and hence rattling tiles. The batten centres are 202mm which translates into a mid range head lap and I am building in a sheltered location.

 

My natural inclination when approaching this task is that before any further slates are layered on a newly nailed slate there might be a hint movement at the nail two holes when lateral force is applied to the slate and this might translate into a mm or two of lateral articulation at the bottom of the slate when high finger force is applied sideways. However is the slate rattles to a finger tap then it is too loose.

 

 

[markc]

Not tight! The nail is only there to stop the slide sliding, you should be able to jiggle it a bit after nailing or they will crack. Hard to describe … sort of snug but not pulling down

[scottishjohn]

wee suggestion-- go through them and make piles of same thickness 

will make them lie better if all slates on same row are same thickness

them ore expensive the slate the more them will be same thickness

I found the ones  Igot to slate my old refurbed explosive shed -which were a £1 a piece varied greatly -but 100year warranty -will outlive me

 

[epsilonGreedy]

Yup already done the grading, but any confirmation is welcome at this point.

 

The following confession will probably trigger some hilarity but I actually used Swmbo's kitchen scales to grade the slates but after the first 50 I could grade them by eye and hand weight.

 

The following in grams for 10x20 slates: 

• 1850 to +2000 = Thick.
• 1700 to 1850 = Medium
• < 1700 = Thin (not many of these).

The more difficult aspect of slate grading is deciding when to reject a slate due to a bend across the slate. A pro restoration slater from a nearby site visited and double checked my grading. He said I was rejecting too many on the bend criteria and he would use some of those.

 

With all my hips and eave slates I should be able to use some of the bent slates where the bend can be cut off. 

[epsilonGreedy]

21 minutes ago, markc said:

sort of snug but not pulling down

 

 

That is the type of phrase I was looking for.

[Thorfun]

my roofer has started today and we're having natural slates fitted so I thought I'd pop out and ask him for you. ?

 

he said the same as @markc in that they shouldn't bend the slate but it should be snug.

 

he also mentioned that the slates shouldn't butt up to each other and there should be a slight gap between them to allow for lateral movement of the roof. thought I'd pass on that little gem in case it's needed.

[epsilonGreedy]

6 minutes ago, Thorfun said:

my roofer has started today and we're having natural slates fitted so I thought I'd pop out and ask him for you. ?

 

he said the same as @markc in that they shouldn't bend the slate but it should be snug.

 

he also mentioned that the slates shouldn't butt up to each other and there should be a slight gap between them to allow for lateral movement of the roof. thought I'd pass on that little gem in case it's needed.

 

 

A champion and timely post, thank you.

 

Does your roofer do FaceTime video consultations?

[Thorfun]

1 minute ago, epsilonGreedy said:

Does your roofer do FaceTime video consultations?

he did mention something about writing a book and retiring. then he realised that he'd be bored sat at home all day so, thankfully for me, is carrying on doing my roof