Natural slate vs composite

[Renegade105]

Hi guys,  

 

wondering on my options of grey tiles for our home.

 

so far been looking at the cheaper Marley tiles vs the Spanish Slate. 
 

as you can see I don’t wish to spend a fortune but equally want it to work well.

 

I think safer bet is the natural slate but I’m curious with peoples experience with these concrete/composite tiles from Marley etc.

 

if anyone can shed some light this certainly would help.

 

thanks All!

[epsilonGreedy]

When you say natural slate "works well" and is a "safer bet" what criteria are you assessing against?

[tonyshouse]

Millions of buildings have roof covered with concrete and non asbestos cement artificial slates, they all work.

 

tiles are cheaper to lay than slates

 

many slate roofs are over 100 years old generally they used Welsh slates (the best) unless you can afford Westmorland ones, Spanish slates are not as durable as Welsh slates 

[markc]

As above, real slate has been used for hundreds of years and proved itself to work well, but as a natural product it has flaws, is not consistent and often breaks when you least expect it.

’fake’ slate being factory produced is very consistent, rarely breaks but does look “too uniform” in places. 

[scottishjohn]

not sure there is much diff in price between cheap slates and tiles -£1 a piece for spanish with 100 year warranty + marley composite were more expensive + more complicated nailed with the rivets required at bottom edge to stop them lifting 

  no need for cross batons if using sarking board -nail direct to through the building paper ,

Iwould agree that once you laid out the battons then tiles are quicker to fit 

 

[Dudda]

Natural will always look better. As markc said manufactured can be 'too uniform' in places.

 

Just want to add that the colour of a natural slate will never fade. Manufactured slates and tiles will. This doesn't happen often but does happen. If you check the small print manufactured tiles and slates might have a 20 or 30 year warranty but that's a structural warranty. As in they won't fall off the roof but the colour warranty is usually much shorter at about 5 years, and 10 years if you're very lucky. We had one project where the slates looked crap after 15 years and are now replaced with Blue Bangor natural slates (very expensive top of the range natural slates - Spanish is a lot cheaper). 

[SteamyTea]

3 hours ago, tonyshouse said:

they used Welsh slates (the best)

People from Delabole will disagree with that.

[tonyshouse]

OK one of the best 

[joe90]

The only thing I dislike about slate is you can’t walk on it like concrete tiles.

[JohnMo]

Depends how thick they are, in Scotland they are specified thicker than in England I believe due to higher wind loads.  Our are 8 to 10mm thick.

 

Walk around a 5 or so year old building development near you, to assess what concrete tiles look like, do the same with any slate buildings. Around us the concrete ones tend to have faded and have Moss on them.  But that could be our weather etc. (NE Scotland)

 

[Faz]

I used the Cedral (used to be Marley) Thrutone manmade slates and am really happy with them.  The benefit is that 1/2 of them don't end up in the garden after the first hard frost!

 

[epsilonGreedy]

@Faz

 

How does a hard frost trigger failures in a natural slate roof? Let me guess:

1. Temperature extremes open hairline fractures in the slate? Or
2. Water under one slate in the overlap expands and levers a slate upwards at the nail fixings? 

I have been up on my roof this afternoon fitting natural slates and now I am worried.

[Faz]

Condensation into the hairline cracks in the slate - freezes and half of the slate busts off and lands in the garden.  I am renting a 100 year old house and the things are still comming off - you just can't avoid it mate.

 

It doesn't look unsightly until it is too far gone in many years time - it is just one of those things and depends on the slate coming out of the quarry - some is better than others and the price point is not a factor.

[epsilonGreedy]

On 14/12/2021 at 18:40, Faz said:

Condensation into the hairline cracks in the slate - freezes and half of the slate busts off and lands in the garden.  I am renting a 100 year old house and the things are still comming off - you just can't avoid it mate.

 

 

Ok. I was thinking that thermal expansion/contraction cycles might open up hairline cracks in slate but now I understand that freezing water can drive that as well.

 

When you say the slate "bursts off" do you mean a large flake of slate breaking away in the plane of the slate rather than a fracture through the thickness of a slate?

 

On 14/12/2021 at 18:40, Faz said:

and depends on the slate coming out of the quarry - some is better than others and the price point is not a factor.

 

 

This is very true. I feel people over simplify the quality issue down to Country-A = Good and Country-B = iffy.

 

 I think it depends on the quarry and the seam of slate being mined at a point in time.

[Faz]

You get some flakes but most;ly the slate just cracks into 2 pieces.  I would say that you would have 3 - 5% of the slates affected in this way in the first winter.  Then it will be a few slates a year ongoing.

[JohnMo]

Never had that issue, last house was 200 years old and part of the roof recovered 10 years ago.

 

Latest house has good quality slates and not seen any issues either.

[epsilonGreedy]

1 minute ago, Faz said:

You get some flakes but most;ly the slate just cracks into 2 pieces.  I would say that you would have 3 - 5% of the slates affected in this way in the first winter.  Then it will be a few slates a year ongoing.

 

 

☹️ Sounds like another reason to fit roll top lead flashing ridges and hips. Much simpler to peel back the flashing and relay a section of slate roof.

 

Having said that a mortar bedded ridge on conventional tiles will start to loose chunks of mortar bedding after 15 years because the underlying wooden roof structure moves. Traditional roofers claim fancy dry ridge systems eventually suffer UV breakdown in the bits of exposed plastic. Nothing is problem free for +25 years.

[epsilonGreedy]

2 minutes ago, JohnMo said:

Latest house has good quality slates and not seen any issues either.

 

 

After fitting about 300 slates I have been surprised at how robust they are. I broke my first slate this week when I copper nail would not bed down flush, I had left my ear defenders on after trimming a slate with an angle grinder and could not hear the hammer collisions.

[joe90]

3 minutes ago, epsilonGreedy said:

Having said that a mortar bedded ridge on conventional tiles will start to loose chunks of mortar bedding after 15 years because the underlying wooden roof structure moves. Traditional roofers claim fancy dry ridge systems eventually suffer UV breakdown in the bits of exposed plastic. Nothing is problem free for +25 years.

I think 15 years is a bit optimistic, my builder only uses dry ridge systems (and so did I before retirement).