Issue with slate recently installed ?

jd6677

Hi,

Just looking to get an opinion/advice relating to new roof slate installed recently. From what I can see it looks like some of the slates are curling at the edges and are not lying completely flat on the roof. From what I understand from the roofer he said the slate is spanish and conforms to T1 – S1 – A1 (seems to be a standard from searching around the web). Is this normal for natural slate to be like this or is there something wrong here I need to address with the roofer?

I have attached some pictures of the roof for reference.

Many thanks in advance,

JD

North West

Hi jd
Looking at your photos. Do you know were the slates graded/sorted before installation ?. It is recommended slates especially natural slate should be graded to light/medium/heavy before fixing. this then leaves you with a uniform installation up the roof. It looks that they were not graded. Fixing then starts heavy at the eaves, medium centre of roof and lights towards the ridge. A lot of slaters do not sort the slates properly as it takes a lot of time.

NW

tabby aspreme

North West wrote: »

Hi jd
Looking at your photos. Do you know were the slates graded/sorted before installation ?. It is recommended slates especially natural slate should be graded to light/medium/heavy before fixing. this then leaves you with a uniform installation up the roof. It looks that they were not graded. Fixing then starts heavy at the eaves, medium centre of roof and lights towards the ridge. A lot of slaters do not sort the slates properly as it takes a lot of time.

NW

+1 they look like they were not graded properly , also with natural slate even when graded some may not sit neatly on a particular slate but would be fine on the next one

mykillokneel

As above should be graded ask your roofer did he grade (he'll probably say yes now anyway!) Some of those slates don't look uniform across the width which is okay if it's on bottom of the slate but not above nail hole as causes lifting as seen. Those kind of slates should probably be left out when grading, you'll always have a little in natural slate but that much looks messy from below

jd6677

Many thanks for all the replies and information guys, this has been very useful.
I spoke with the roofer today and he said he sorted and graded the slate and that was the best it could turn out.
I'm not sure what my next plan of action will be yet with the roofer - any ideas?

Thanks
JD

baby fish

grading if the first step for a top notch job, but even after grading the slates need to be fitted to each other when fixing them, its not as simple as throw them on like the manmade slates, e.g. a few slates might have to be tried in one position to get the slate that fits without rocking. It takes time and effort to do it properly. there are definitely some "heavy/medium" slates beside "light" slates on your roof so it doesn't look like too much effort or care went into fixing them.

Grading is for thickness, lets say this was done perfectly, when actually slating the roof you will come across some twisted and cupped slates. These need to be put to one side or they just kick up at the end or kick up the slate that is laid over them.

I hope I don't offend you by saying it could be a combination of poor roofer with a slate at the cheaper end of the scale? the more expensive slates are better quality and flat, but a roofer that doesn't care will do a bad job with anything.

another thing to note is the rafters have to be at least straight or even with a dip in them for the slates to sit without sticking up. if there is a hump in the rafters then this can mess up how the slates sit.

jd6677

Many thanks baby fish for your honest and very useful information/assessment of the roof.
I'm going to dig a little on what the slate is and why the roofer didn't don't look to be sorted and graded. I'm due to get some 50 year warranty cert for the slate - so will be interested to see that.

Thanks again,
JD

bertie 56

One question here :

How fast was your roofer to do this ( poor ) job ?

And accessory, did your roofer follow all these steps ?

- Grading should be done on the floor, before putting them on the roof.
It should be graded in 3 piles, but ideally in 5 piles ( very light / light / medium / heavy / very heavy ).
( For giving an idea, some slates weights the double of another one, that means it is twice the thickness ! )

- The different crates should be mixed. How often do you see this on site ??? You never know if the crates comes from exactly the same vein of rock when extracted, and some difference in colors can be seen between two different crates .

-Even with good quality slates, you have to choose and select the slates . It's often that you take a slate and put it apart because it doesn't go into place. That doesn't always means it's a bad one, it just means that it doesn't go into this precise place. Try another one. And do it again if it doesn't work. It happens for me ( rarely, though) that I try 20 slates before finding the right one !
Some slates are too crooked, they can't be fitted on a roof . Keep them for a plane manufacturer, they are good to make propellers.

To recognized a good slater at work, look at him working : If he takes one slate and nail it straight away, every time, you will have a roof like your pictures, 100 % sure. ( ask him to go down the roof and tell him they are not the manufactured fake slates, in case he didn't see )

If he takes a slate, try it, put it aside, take another one, look at it,try it again, etc, and fit it only when he is happy, then you'll probably have a good roofer there !
Now, unfortunately, these ones don't work anymore, they are too slow and expensive for most of the people !


I wouldn't trust much the "50 years guaranty", though. They are about the quality of the slate itself, not about how they are on the roof. And who knows what will happens to the quarry in the next 50 years anyway ?
And by the way, with an A1- S1-T1 slates ( if the certificate is recent ! ), you won't have to worry about the slate itself , but more with the way it sits on your roof.

Are you in a windy area ?

jd6677

Hi Bertie – thanks for your thoughts and information.
From what I know the roofer did not sort the slate on the ground – there was two crates and he moved it straight from the crates to the roof after the initial slate was stripped. I don’t think he mixed them at all. I didn’t see the roof being fully completed but when I did see him working it was quick in terms of nailing down the slate. I’m also not in a very windy area in Dublin.

Thanks,
JD