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How to choose the best roofing slate for Melbourne weather conditions

So how do you know what to look for to determine the best roofing slate for Melbourne ? I’m not going to get into all the technical jargon about what slates are composed of but just some real world observations from someone who has been around Melbourne slate roofs for 37 years.

I’m just going to point out a few factors that I’ve found to determine what I consider is the best roofing slate for Melbourne … longevity. appearance and functionality.

Currently in Melbourne if you search hard enough you’ll find quite a few different types of roof slates available. The main ones being Chinese, Indian, Spanish and Welsh.

Chinese and Indian roofing slate.

I’ll just come right out and say it ” I am not a fan of any of the past or current Chinese or Indian roofing slates”. Over the years I’ve been approached by various companies, most of whom know nothing about good slate, but import them along with garden furniture, light fittings and the like. They want me to buy and use these slates on my projects. Sure, they are a little cheaper but the quality is just not there.

Let me just list a few of the things I notice about these slates.

1.
They can be very soft, not to the untrained eye,but to the trained eye its obvious; hence they don’t last very long.

Case in point here. In the early 90’s we were contracted to supply labor only to install a Chinese slate that the homeowner had imported himself, along with other goods for his own business.As soon as I saw and handled the slates I knew there was going to be heartache somewhere down the track, but the owner was very excited about the “saving” he thought he had made so we just bit our tongues, installed the roof, and moved onto the next job.To cut a long story short we re-roofed the home some nine years later with a good quality slate. The thinner slates in the upper courses of the original roof were virtually disintegrating and I would say that given time the others would have eventually followed.

That roof was a real eye opener for me as to the low lifespan of poor quality slate. I don’t think the owner was too impressed with his investment either.

2.
The thicknesses of the slate vary a lot.

In many instances this isn’t a bad thing, you can grade them into more groups, but it is the different thicknesses on the INDIVIDUAL slates that cause all the problems.
These things can have quite a bit of variation as well as humps and bumps; hence, try as hard as you will it’s very difficult to get a nice even, tight, flat sitting roof. There will be slates cocking up everywhere and it’s very unsightly.

One very important characteristic of good roofing slate is that it splits very evenly producing a nice flat even and dense slate.

3.
Not all, but many of these slates contain pyrite which is a type of iron ore which as we all know oxidizes (rusts) when exposed to the weather.

I do not like pyrites. Some slates with pyrites are claimed to be non-rusting but in my experience you just can not trust how they will react with the atmosphere. Depending on the amount of pyrite in the slate, some roofs will only leach ugly brown stains down the roof, but on others I’ve seen, many of the slates rust out with full perforations the size of 20c coins… not good.

4.
Many of these slates also contain varying amounts of calcium carbonate.

Calcium carbonate in slate causes fading, not an even fade, but inconsistently. If you like a chequer board appearance from your slate roof, then consider it a bonus and not the burden that most homeowners consider it to be. The calcium carbonate reacts to the suns uv rays and causes a softening of the slate as well as the discoloring. Over time this softening leads to porous slate and much leaking and eventual replacement.

5.
Contrary to point No. 1 some of these slates can be hard enough but very brittle.

When working with these slates you can never be sure that when you hole or cut them, or even from just handling them, that there is no invisible fracture which eventually breaks sometime in the not to distant future.

There is one particular roof that “springs to mind” as I write this. This roof was installed about eight years ago to an existing home, by whom or what the slate is called we have no idea, we only know from the owner, that it is a Chinese slate. For the last seven years we get calls from the homeowner probably twice a year to replace slates that continually snap between the nail holes. The result is the lower portion of the slate sliding down the roof, subsequently exposing the joint below, causing a leak. Needless to say the owner is extremely frustrated and in his own words “wishes he had looked into it considerably more before choosing the Chinese slate for the meager saving”. The only permanent remedy for this roof is to completely re-roof with a good quality slate. At around $30,000 not an option for the owner at this time but in a few years it may be an option he can’t refuse.

I’m not sure how many of these particular slate roofs are out there but we come across and repair a few of them from time to time and this defect is common to every one of them. I can’t remember who it was that came up with the name but these roofs have quite aptly been dubbed as “snappers”.

It’s pretty hard to consider these slates for the title of ” best roofing slate for Melbourne “

Spanish roofing slate.

Moving onto the slates from Spain. At their best they are one of the finest slates in the world, and at their worst they are not much better than the Chinese or Indian slates. All of the above points apply to the low quality Spanish slate.

I have installed a couple of varieties of Spanish slate over the years with varying results.The ones that I installed first had to pass my close up inspection for pyrites, splitting qualities and general feel.Were they too soft, did they feel too brittle, that type of assessment. Of the few different types that I installed, I have kept a close eye on them over the years and while I can say they are performing OK, they have a few little things that annoy me, purely aesthetic, not their structural integrity. Aesthetically they just don’t quite sit as nice and flat and tight together as I like.

At the other end of the Spanish scale is my personal favorite roofing slate, there just isn’t a better slate, value for money wise, on the market at the moment. My biggest reason for this being my personal favorite slate is that it passes and is still passing, my number one slate test, with flying colors. That test, is the test of time, being personally watched and verified by my very own eyes. Back in 1982 my mentor and I installed an extension and re-roof using Spanish Del Carmen Ultra roof slates.
Peter had used these slates back in Scotland for many years prior to this job and he really liked the way they handled the freeze thaw cycles,showed no rust signs and sat beautifully on the roof. He had installed a few of these slate roofs in Melbourne for a couple of years prior to this one and was very confident they would perform well. I have watched this roof closely over the years and it is as good now as when it was first installed.
About 18 months ago I had to assist a solar energy company install solar panels on this roof so got to inspect it very closely and apart from the moss it is no different than when initially installed all those years ago.

Welsh roofing slate.

Welsh roofing slate has a long history in Melbourne. Beginning around the mid 19th century up until the 1920’s when slate fell out of favor as a roofing material. Recently they’ve made a return to present day Melbourne homeowners and builders.

With a few exceptions they are a very good slate and still serving many of our original period homes quite well. The Welsh slates available today are evenly split, durable and sit nicely on the roof. However, their major drawback is their price. When you compare the qualities of the best Spanish slate to the Welsh they are identical in all aspects. The major point in difference here is that at around double the price of their Spanish counterparts it’s very hard to justify their expense.

Conclusion

So what is the best roofing slate for Melbourne.

I have not yet come across a Chinese or Indian slate that I’d be happy with on my own home. There may be one out there somewhere but I haven’t seen it yet. I’m not saying there never will be one either maybe one day but I’d still be wary until it passed my test of time. Best quality Spanish and Welsh are equal in my book. The Spanish comes with a 100 year quarry manufacturer guarantee and are certified by French NF standards … the most rigorous testing in the world. The Welsh are also very durable but it’s hard to justify their seemingly exorbitant cost. At almost double the cost of the very best Spanish slate it can add up to a considerable amount. Don’t get me wrong, if someone really wants Welsh slate I’m happy to supply and install but because of the cost it’s hard to understand why when its Spanish equal is half the price and looks and performs just as well.