Welsh roof slates flaking / delamination - are these bad?

[DIYNotIan]

Hi all

Whilst doing some repairs on my roof - which required removing some slates - I've noticed that a lot of them were wet on the underside. They are also flaking, a bit on the underside, but more on the upper section of the topside (the sections covered by the slates above). I'll attach some photo examples, and wondered if anyone familiar with slates can say whether they look bad.

My roof has sarking boards, covered in 1f felt, and they only used horizontal battens. So I guess there's no ventilation between the sarking/felt and the underside of the slates. Is this the likely caused? Or perhaps they're just getting old (I know the feeling!).

I should add that the battens all seem fine. Would they not show signs of mould or rot if lack of ventilation was a problem?

Cheers

Link to photos. Sorry, they're not the best. Can take more if needed

Slates Flaking – Google Drive

drive.google.com

 

[catlad]

Seems queer to have batons on sarking and not to be counter batoned !
The slates are reclaimed and don't look to great but will keep the water out for another 30 yrs if maintained.

 

[DIYNotIan]

Seems queer to have batons on sarking and not to be counter batoned !

Now that I understand more about roofing, that's exactly what I thought too! It was done well before we moved here, and I don't know by whom. Shame.

The slates are reclaimed and don't look to great but will keep the water out for another 30 yrs if maintained.

I'd be more than happy with 30 years! In terms of maintenance, what kinds of things do you mean?

Do others agree that they might last that long? A fair few have been off the roof for the repair work. Some still ring nicely when tapped with a knuckle, does that mean they might be better than they look at first glance?

Many thanks

 

[datarebal]

If they ring they are good .
Rattle or thud .. no good

 

[DIYNotIan]

Excellent. I've weeded out all the slates that rattle or thud. Of the ones I've kept to re-use, some certainly ring more than others, but I wondered if that has something to do with the thickness of the slate and/or anything else? Some ring high, so low, etc. But basically if it rings and you can feel it vibrate, then I count it as good.

If they ring they are good .

So do you think that's the case even if they are flaky/delaminating on the top as per my photos?

Huge thanks for the help

 

[catlad]

Maintenance is just replacing cracked or missing slates.

 

[datarebal]

Obviously you will get a different note from differing thicknesses. But you should be able to hear good from bad.

 

[DIYNotIan]

Maintenance is just replacing cracked or missing slates.

OK, thanks for explaining.

Obviously you will get a different note from differing thicknesses. But you should be able to hear good from bad.

I think I've got it now. I read a while back that once you know, you know. And I think I know! Rattling slates are obvious. Dull I'm not certain but I think it's when they just thud and sound lifeless. Ringing is when they subtly vibrate in your hand and ring on, low pitch for thicker slates, and higher pitched for thin.

Thank you both for the help. I'm re-assured and less stressed now if these should do another 30 years or so., especially if that is the case even without ventilation between the sarking boards/felt and underside of the slates.

Cheers