|Posted on Sunday, February 12, 2006 - 12:02 pm: ||
I am a builder based in the England who occassionally undertakes roofing projects. I have a couple of questions I would like your thoughts on:
1) In England most slates appear to be centre nailed whereas in the US you appear to hole your slates higher up. Doesn't this mean your slate will be more susceptible to the effects of wind suction?
2) Would head nailing 'heavier' slates be an acceptable way of combating wind suction? My thinking is I would be able to buy a cheaper shorter slate that covered the same area.
I have been reading this site and enjoying the content immensely.
|Posted on Monday, February 13, 2006 - 05:09 am: ||
In answer to your questions,
1) In the U.S. the slates can be nailed slightly higher because they are nailed directly to boards, whereas in England the fact that we nail to battens means that the holing needs to be more accurate. Having said that, I don’t see that the difference is big enough to affect the soundness of the roof.
2) Would head nailing 'heavier' slates be an acceptable way of combating wind suction? Are we still talking about slates here, or are the heavier slates actually “stone”. If we are still talking about slate, then my opinion is that head nailing is never as good as centre nailing. Regards. Mjh.
|Posted on Monday, February 13, 2006 - 05:40 am: ||
Thanks for the reply mjh.
Is centre nailing preferable to head nailing because of it's cantilever properties that help with wind suction? Are there other reasons why it is better?
|Posted on Monday, February 13, 2006 - 02:33 pm: ||
I have run across slates nailed nearly mid-point, and others nailed at about the upper 1/3 line. The 9x18 that I am installing now are punched at roughly the 12" mark, +/- and inch or so. I am installing it on 1"x4" lathe, so the variance is not a problem as it would be on 1"x2" lathe. The slate I am removing is 12x24 nailed just above mid-point on 1"x2" lathe. That slate was probably put down in the 1940s or 1950s.
With a proper head lap (3") there is only 7.5" of exposure on an 18" slate, so "wind suction", or lifting of the slate during high winds, is unlikely to be an issue. If winds are high enough to pull slate off a properly nailed slate roof, there are likely to be more significant issues to deal with than missing slates!
My experience is very limited, so others can surely add more to this discussion than I.
Jim K in PA