From a different topic:

Regarding sizes and weights/thikness of slates,it is largely due to practical reasons that slate is more popular in thinner sizes.A ton of thin slates ,if all uniform size will cover a greater square area than the same wieght of thicker slates.In other words,1000 thick slates take more space to back,and require more haulage cost than the same number of thin slates.Also for handling,and carrying up a roof you could carry 20 countess`slates up a ladder,but if the same sive slates are say twice as thick you are not going to be so fast.If you are into stone slab roofing,you would only be able to carry 1 up a ladder if it was say 2ft x 3ft.Also lighter slates as opposed to thick slabs,are ideal when british practice is to use as little wood in roof construction:In scotland and america roofs are boarded to carry the weight of snow,where as in england and wales roofs are battened.Generally when slate arrive to a job thy are `sorted into 3 or 4 groups,according to the slight differences in wieght,thus enabling slates to lay flat.If you put a thick slate by a thinner one you have what is known in the trade as a `laugher`.

Indeed, but...

I think that modern slates have become too small and too thin.

I'm sat in a house roofed with what's probably Penrhyn slate, but it's a modern house and thus they're modern slates.

To my mind, they're too thin and this causes them to rattle more; and to be more prone to cracking - several have cracked despite the roof only being 12 years old.

A thicker and larger slate would - in my opinion - be better suited to resist wind and rain and although there's an obvious economy in using thinner slates, it's not necessarily the best of ideas.

---

Thin slates are great when new and from a good quarry such as penrhyn.second hand slates are often fine for re use,yet I agree that slightly more thicker slates often look better and provide a stronger roof.Thin slates particularly second hand ones are more prone to rattling in adverse weather over time.The succes of any slate roof new or second hand depends on the initial sorting and grading.if this isnt done the roof can fail,in a number of different ways from day one.I think penrhyn supply a thicker grade of slate (celtics or countys? cant remember at the moment) that are poular with some.
Personally if I were to build my own house from scratch I would use slate over tile any day,and would hook every slate-would be bomb proof.And easier to maintain.
The europeans are keen on this method,not often seen in the UK though.
More power to Ffestiniog and Penrhyn.The E.U has really opened the flood gates for Spanish slates.It is a shame this country values economy over quality.

it's long been the case here.

It's because we have a tax regime of long standing which does not encourage investment, a banking system which has completely abandoned the concept of 'duration of return' in favour of the next quarters' results, a bi-polar, adversarial electoral system which for the past 30 years has been debased to an arena in which two radically opposed ideologies have fought each other to exhaustion instead of running the country, a class of professional politicians who graduate straight from student union posturing to government.

I was listening to Any Questions on Friday, with various ideologues posturing about the question of MP's pay. I don't happen to think that a salary in the £60 - 100,000 range is excessive for a senior MP, or £60,000-plus for a long-established back-bencher on Committees; but why is it automatically acceptable for the schoolgirl recently returned at Norwich? And not one of them questioned this....

we also have far too many lawyers in parliament who are primarily interested in nit-picking and the most slavish and literal interpretation of laws which our European opposite numbers treat as a pick-and-mix counter to dip into as they see fit, and ignore as they suit.

our bi-polar politics mean that no-one dare challenge the shibboleth of the client state of benefit dependents, swollen tertiary education of ever-decreasing value and unproductive public sector employees.

apart from that, we have no problems...

---

Slates on my house are too thin as well. But given I live about 300 yards away from Vanoord it's hardly suprising :lol:

Vanoord, do you know if they're local or imported? There'd be a certain irony if they were imported...

---

I would be surprised if the local planning department had allowed them to be anything but local.

That said, they can now only specify slates that are of a similar colour to local slate, which does allow Spanish slate to slip in.

Whether or not that rule was in place 12 years ago, I don't know?

---

Well at least "bringing slates to Ffestiniog" could replace "carrying coals to Newcastle".

---

WCMS are in the process of renovating a place to use in the Brecon Beacons. It is a nineteenth century cottage with a slate roof. We managed to keep a good proportion of the original slates, were offered a job lot of old slates from a nearby property that were in good condition, but the shortfall was sourced by our builder from overseas. Only these latter slates were required to be handled with care owing to their extra brittle nature. Sad, really.

I have a poor sense of past time but it does not seem very long ago (10/12 years maybe) that the local authority got a lot of bad publicity for using foreign slate on one of their buildings. Portmadog area but I cannot remember which building it was.

---

Intrestingly Snowdonia National Park use to have to have Welsh slate intsalled,but now the E.U specifys that Slate of European origin can be used.You are not allowed to specify.
Funny to go for a ride on the ffestiniog railway and spot the Spanish slate.
I think with second hand slate,getting a good roof depends on selecting the right slates,whatever the thickness.Good to know your supplier and the quarry they came from.Thin slates sorted and nailed properly should function well,provided they are good quality,still have the all important tensile strength,and are flat (notice with spanish slates,particularly poorer quality ones,that if you look down the length of an individual slate,they tend to be warped,or slightly twisted;best way to deal with this is to chop off the top corners,known as shouldering).

To my mind, they're too thin and this causes them to rattle more; and to be more prone to cracking - several have cracked despite the roof only being 12 years old.

A thicker and larger slate would - in my opinion - be better suited to resist wind and rain and although there's an obvious economy in using thinner slates, it's not necessarily the best of ideas.

Quite agree. Our roof is just coming up to 150 years old and large parts of it are completely sound and untouched from the day it was built. These are the bits using Duchess (24x12) slates of medium thickness. Though I think that counts as "very thick" in today's terms.

Other areas with Countess slates were in a poorer condition. Not usually due to a failure of the slate, more due to generations of thieving ignorant roofers. Main causes of failure are:

- walking on the slates instead of using roof ladders
- using galvanised nails instead of copper
- makeshift straps made of lead, not copper.

:curse:

When you look at newbuilds using slate these days, quite often there are slates that just seem to have fallen out of place.

Always the case that steeper pich slate roofs last longer than lower pitch ones.You are less likely to get a window cleaner or satellite ariel man on a steep pitch,smashing them to bits.Steep pitches function better as they shed water faster,thereby delaying feeze-thaw degradation and delamination.As a general rule of thumb lower pitches need shorter and wider slates eg 18x12 would be a good size for a 30 degree pitch if you used a 4 inch lap on them.Same works the other way eg 24 x12 on a steeper pitch with less lap.All to do with water `creep´to the nail holes, and sidelap.If you have second hand slate that have to be re holed (if original holes are worn to big) you are holing further away from the edges of the slate and increasing the chance of water spreading to the holes....
Perhaps I should my change name to slate anorak...
Anyway,I hope its of some interest.I also put some photos from the last 4 years on the Dinorwic user album.Maybe
of interest to fellow slate fans.The place never stops to amaze,in any wether.

Aficionados and anoraks (hi blondin!) might be interested in:-
www.stoneroof.org.uk/cnts.html#Top
www.slateroof.co.uk/invest2.pdf

Enjoy!

cheers!also of intrest might be jenkins slate.com.An American roof slater,who publishes his own Slate Roof Bible`(ISBN 0-9644258-1-5).Second Edition has some intresting German slate roofing in it.Some of the technical info is more relevent to American practice but still worth a look.
Also a good book though a little out dated my grandfather had the same book when an apprentice) is Roof Slating and Tiling by Frank Bennet and Alfred Pinion.Both are available through amazon,and deal at a glance the history of slate (the former has quite an in depth section on U.S quarries).Technically,of limited use but worth a read.The fundamental principals are still there.

It is actually wiser to use a thicker and larger slate for the roof. They are quite stronger and longer to break. Most of the old slate roof has a bigger and thicker slate.

It's down to the builder to buy a 'better' slate, but they build houses with a calculator.......thinner slate( cheaper) = less weight = less timber = cheaper build (more profit).

---

Up here in the northwest we dont ever see new welsh slate it's all chinese italian and spanish
for a 24"x 12" you can pay as little as 0.72 p
the same secondhand welsh slate would be £1.80 p
i belive that a new welsh slate is about £3.50 but as i never see them i dont know if that is true

Up in Yorkshire there are alot of forign slates being used due to cheepness. Unfortunatly you have to watch out for the twisted ones and they twist when installed. The slates are better nailed. With second hand slates it is better to drill any new holes to stop the slates breaking.
You find the thicker the slate the larger the size. With the Welsh and Cumberland slate they used to come flat and were easy to lay. The forign ones are now coming where you have to use wire clips which are exposed on the face so you don't have the big overlap. The clips allow you to use the twisted slates. But do not walk on them.
Theifs are now stripping stone and welsh slats off empty houses, the few that are left. My last bungalow had about 56 ton of stone slate on it.

---