slate types?

[jungle_jim01]

i, i've just started planning on re-roofing a small annex in slate. The roof angle is 21
degrees so from what i've read i need a 4" headlap but i'm struggling to work out which slates to use. My local builders merchant stocks spanish slate at 96p per slate (12"x16"). The roof isn't really visible so i just need something that will do the job.

thanks

 

[jungle_jim01]

just seen these...prices seem good. Does anyone have any experience with them?
http://www.bethesdaslate.co.uk/catalogue/reclaimed_slate.php

 

[Penners]

No personal experience, but the reclaimed 12 x 16s are more expensive than your Spanish ones. And I wonder what guarantee you get that 100% of the reclaimed stock will be good. A proportion of unusable slates will soon push up the unit price of the good ones.

If there are no aesthetic considerations, I would choose the cheapest (provided they really are the cheapest!).

I'm no expert but 21 degrees sounds a bit tight for slates. What's the orientation of the roof? Is it subject to heavy weather - particularly wind blowing towards the face?

 

[jungle_jim01]

Thanks for the reply. I'd wondered about the angle. From i've found out 20 degrees which is about the minimum as long as there is 4" headlap. The roof's in a sheltered location so wind against the face shouldn't be an issue. I've been reading articles from the following site which seems pretty comprehensive...well worth a look if you're interested in roofing: http://www.traditionalroofing.com/TR6_headlap.html

 

[MdB]

Thanks for the reply. I'd wondered about the angle. From i've found out 20 degrees which is about the minimum as long as there is 4" headlap. The roof's in a sheltered location so wind against the face shouldn't be an issue. I've been reading articles from the following site which seems pretty comprehensive...well worth a look if you're interested in roofing: http://www.traditionalroofing.com/TR6_headlap.html

It sounds like that site knows what it is talking about but the 4:12 ratio works out at being 18.4 degrees. This sounds very small to me (no expertise in this whatsoever) even with a 4" headlap. The calculation also doesn't take into account the size / thickness of the slates which will affect the results so I would be wanting to look into it a bit further if it was me.

 

[Penners]

the 4:12 ratio works out at being 18.4 degrees. This sounds very small to me (no expertise in this whatsoever) even with a 4" headlap.

I would defer to your mathematical skills every time, MdB, but I don't understand that calculation.

Presumably 45 degrees is 12:12, therefore 4:12 is one third of that. Wouldn't that be 15 degrees?

I do agree with your concern, though, whether it's 18.4 or 15. That's extremely shallow.

 

[middi]

If your slates are not more than 8mm thick and with a 4 inch ( 100mm) overlap, you will be extremely safe ( bar a typhoon ) as long as you allow for a min. pitch of 18 deg. ( I have used them at 16.5 deg on an existing roof with no problem).
( use copper nails, galvanised clout nails do not allow slates to be completely close to each other, therefore more gaps and prone to be dislodged by high winds)

Middi

 

[Penners]

galvanised clout nails do not allow slates to be completely close to each other

Why is that, Middi? Is it the thickness of the nail head? I've used galvanised plasterboard nails in the past - the small head sat quite neatly within the countersink in the slate.

 

[middi]

galvanised clout nails do not allow slates to be completely close to each other

Why is that, Middi? Is it the thickness of the nail head? I've used galvanised plasterboard nails in the past - the small head sat quite neatly within the countersink in the slate.

I have used galvanised nails with reasonable success but always found that a few odd slates always "stick up" and that annoyed me. Also in the event of a poor countersink situation the copper nails heads are much more thinner and malleable therefore can be " squashed" closer to the slates.

Just an observation and ease of application on my part.

Middi

 

[middi]

....( a lot of the earlier slates were secured using lead nails )

 

[Feltwell]

You can get aluminium roofing nails now as well - purely because copper is so damn expensive these days! They're fine to use, as for durability I guess time will tell.

 

[Penners]

I can't hammer in copper nails without bending the bl**dy things.

 

[AMc]

jungle_jim01 - I did a lot of sourcing for wide duchess (12"x24") slate a couple of years back and came up with a variety of costs and options.
It was fairly arduous esp. as I was hoping to get a reasonable match to the remains of my existing roof.
If you'd like a copy of the notes I made with names, numbers and prices then drop me a PM.

 

[CliffordPope]

If you have felt underneath then it doesn't really matter about the angle?

 

[Penners]

If you have felt underneath then it doesn't really matter about the angle?

What a coincidence. That's exactly what I used to say to a past girlfriend of mine.

Yes, the angle still matters. Felt is a good second line of defence, but it's not meant to take the place of an effective roof.

 

[another_richard]

When I used to help out a roofer in my younger days I seem to remember thick slates near the gutter medium in the middle and thin at the top.

Do all slates come in the same thickness today?

 

[middi]

If you have felt underneath then it doesn't really matter about the angle?

What a coincidence. That's exactly what I used to say to a past girlfriend of mine.

Yes, the angle still matters. Felt is a good second line of defence, but it's not meant to take the place of an effective roof.

:lol:

(That's disgusting Mr P. :wink: )

 

[middi]

When I used to help out a roofer in my younger days I seem to remember thick slates near the gutter medium in the middle and thin at the top.

Do all slates come in the same thickness today?

Only the " plastic" ones are exactly the same thickness. Real slate will always have a degree of thickness variation.

 

[Penners]

If you have felt underneath then it doesn't really matter about the angle?

What a coincidence. That's exactly what I used to say to a past girlfriend of mine.

Yes, the angle still matters. Felt is a good second line of defence, but it's not meant to take the place of an effective roof.

:lol:

(That's disgusting Mr P. :wink: )

Disgusting? :shock:

Did I not make it clear that I was trying to teach my girlfriend how to re-roof her house?

 

[AMc]

"re-roof her house"? I've never heard it called that before...