Slates -vs- tiles

JustAnotherSaver

Aside from the obvious answer of cost, is there any benefit / disadvantage to having slate over tiles?

Also discounting looks too because that's all personal opinion. I'm talking actual benefits/disadvantages?

Story short, house in question was built 1895-1905 timeframe. Old detached cottage and in my opinion it'd just look better with slate. There's approx. £1k difference with the slate cost coming in around £6.5k and the tile quote coming in around £5.5k so for the sake of £1k I think the owner is going to opt for slate as they would just look better on a house of this age.

But what are the actual benefits / disadvantages of going for one over the other?

And to take it a step further on to my own house...

My house is a 1930s semi which currently has slate. On the underside of these is white globs which fall off and land all over the chipboard flooring in the loft. Very bitty/dusty up there. You can see the underside of the slate very clear.

Some houses in the local area, same design as ours actually, have had re-roofs recently - with some going slate but others going tiles. A few questions here...

I suspect they didn't have things like breathable membranes back in the day whereas these days they use all that stuff. So first off would you expect any problems by modernising the roof (even if you replaced original slate with new slate but the whole roof was just re-done to modern standards?

I'd like all this crap that's falling on to the chipboard flooring in the loft to stop - would you expect that with a re-roof? I have a very very loose understanding of what's involved so the answer to this may even be it's impossible to happen under modern specs for all I know.

The house was designed to have a slate roof and from sticking my head up there, it is very very breathable because I can feel the breeze and see daylight. If you switched out for tiles, similar to the first question on my house, would you expect potential for trouble? I'm talking about things like damp as there may be less air flow (maybe there wont be less, I don't actually know - I'm just asking the question in advance for whenever we can afford to getting it done).

Doozergirl

Slates are also tiles, so you're not specifying what the alternative is.  The logical alternative is lightweight fibre cement tiles which are made to look like slate, but cheaper, and durable.   Actual heavy, thick,  concrete tiles aren't suitable for the timber structure of many older roofs and so you get sagging without additional timber bracing.  Best to be avoided.  

A new roof with membrane will stop your bits falling through. The covering is just a covering, it's your spacings and ventilation underneath that keep it all cool(ish) and dry.  You won't cause issues with that, regardless of covering. 

There are different qualities of slate because they are a natural
product.  They come from different seams in the earth and are graded differently.  Welsh slate is widely regarded as the best but you won't be buying that unless you own a very special house indeed.  Spanish and Chinese slates are generally inferior to that and some more inferior than others. They are labelled with quality grades, a bit like timber is.  

Really, if you have an ordinary house in an ordinary street where your neighbours have replaced with all sorts, then a fibre cement slate is perfectly adequate.  They can be moulded to look like more like a rough hewn slate  and from the ground you can't tell much of a difference.  

We have a new house and I was perfectly happy to have smooth fibre cement slates.  The house is modern, the look is clean and I hugely prefer them to the big bulky things that developers put on houses. 

daveyjp

I'm surrounded by Victorian/Edwardian houses which originally had Welsh slate roofs,  a few still have them, but most have changed to tiles.

Of those I have seen being done none of them had the rafters strengthened, just new battens and felt, and ridge sagging is now evident on a number due to the extra weight the original beams are now carrying.

If swapping slate for slate you need to source replacements of equal quality, which won't be cheap.  A lot of foreign slate does not stand up to UK weather and within a few years they will be splitting and falling off.

stuart45

JustAnotherSaver said:

I'd like all this crap that's falling on to the chipboard flooring in the loft to stop - would you expect that with a re-roof? I have a very very loose understanding of what's involved so the answer to this may even be it's impossible to happen under modern specs for all I know.

It's lime mortar known as torching. With a re-roof you won't have it, there will be a membrane under the slates instead.

FreeBear

JustAnotherSaver said: My house is a 1930s semi which currently has slate. On the underside of these is white globs which fall off and land all over the chipboard flooring in the loft. Very bitty/dusty up there. You can see the underside of the slate very clear.

The white stuff is probably a lime mortar. Before felt and breathable membranes were used, it was a common practice to apply a layer of lime mortar (called torching) to the underside of slates & tiles. This helped to plug the gaps, secure the slates/tiles in place, and reduce the risk of wind getting under them.

On my roof, I have some local read with lime mortar slapped on as a base layer - Over the last ~90 years, much of it has fallen away covering everything in the loft with dust. Most of the clay tiles are still serviceable, and a reroof is on the cards.

JustAnotherSaver

I work for a builders supplier so when i say slate vs tiles i'm going off what we refer to as slate and what we refer to as tiles. I appreciate those actually doing the job, roofers, builders etc. will/may refer to things differently.

Roughing bead and angle bead get me every time. Angle bead for us, roughing on bead for some customers, but then you get even further complicated when some others ask for an angle bead but they actually mean a skim bead.

But we're getting off topic.

To explain better I mean this:

TILES:

1) https://redland.co.uk/products/slate-range/mini-stonewold

2) https://www.manninghamconcrete.co.uk/quinn-western-slate-tile/

and others like it

SLATE:

1) https://kdc-pam.southlakeland.gov.uk/NorthgatePublicDocs/00280485.pdf

2) https://samaca.com/wp-content/uploads/2019/06/33-web.pdf

Hopefully from them links it makes sense as to what i'm referring to now?

Doozergirl - know exactly what you're saying regards inferior quality just from handling them. Some are pretty decent but others just snap in your hands for fun and it's not even an accurate rule that the thicker the slate the less likely they are to snap. I've had some thick slates go in my hands when handling them and i've not even been rough.

Our house has what I call a slate roof.

The diner extension which I believe was built in 2000, so before we bought it, has what I call a tiled roof and if the 1 tile that was in the shed when we bought the house is anything to go by then the tiles are actually Redland Mini Stonewold. We have a hole in one of these already.

So aside from cost, why would you pick one over the other? Advantages/disadvantages?

As the person I was talking about is much closer to a re-roof than us (will be next Spring), I'm hoping they don't get stung by someone who will end up doing what you describe. I imagine any fool can throw a roof up, but not anyone can do it properly. You talking about things sagging - to me that's just someone who either isn't educated enough or someone who couldn't give a damn, they'll be long gone with your cash before you get to complaining. It's things like this I'd like them (& myself if I get round to having mine done) avoiding.

stuart45

In the trade most people mean natural or fibre slates when referring to a slate roof. 
Tiled roofs usually are either concrete or clay tiles, although there are metal such as Decra and plastic. 
Natural slate, especially Welsh is normally regarded as the best, although not the cheapest. 

plumb1_2

Eternit slates, make sure copper nails are used

fenwick458

JustAnotherSaver said:

There's approx. £1k difference with the slate cost coming in around £6.5k and the tile quote coming in around £5.5k so for the sake of £1k I think the owner is going to opt for slate as they would just look better on a house of this age.

you need to find out what type of slate, there are many.
Cumbrian or Welsh slate is the best, Chinese or Brazilian is rubbish and worse than concrete tiles by a long way
slate is way more labour intensive to do a roof, and the materials cost more so for a decent slate roof I'd expect much more than a £1K price gap and I think the quote you have is probably for Chinese stuff. 

neilmcl

stuart45 said:

JustAnotherSaver said:

I'd like all this crap that's falling on to the chipboard flooring in the loft to stop - would you expect that with a re-roof? I have a very very loose understanding of what's involved so the answer to this may even be it's impossible to happen under modern specs for all I know.

It's lime mortar known as torching. With a re-roof you won't have it, there will be a membrane under the slates instead.

Always wondered what that was called. My roof, or rather my loft space floor is covered in it 

neilmcl

The biggest advantage by far for real, good quality slate is longevity. A slate roof can last indefinitely, it will be the fixings that fail first. There's a lot of housing stock, mine included, with original slates going back 100 years and more. It's also much lighter than tile.