Green Building Forum - Don't use slate and a halves? Or use them but with thicker slates? Tue, 19 Dec 2023 07:08:30 +0000 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301971#Comment_301971 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301971#Comment_301971 Mon, 12 Jun 2023 21:02:53 +0100 greenfinger
I've got some repair work to do soon on a single storey roof that abuts a gable end wall. The leadwork was pretty shoddy before and needs replacing with proper lead soakers and flashing. As such, a couple or rows of slates will be coming off.

I've heard it's best to use slate and a halfs where possible, rather than thin width sections of slates. But upon enquiring it seems you don't really get slate and a halves in reclaimed Welsh slates. So that leaves me two options...

1. Forget about slate and a halves, use thinner width slates as needed, and carry on.

2. Use larger format but thicker slates. One rec yard has 30" x 20" slates which could be cut down to almost slate and a half (24" x 20"). The existing slates are 24"x 14". The trouble is that these slates are quite thick compared to the existing. I've never done and am no expert on roofing so am not sure whether the slates being thicker would cause more problems than I'm trying to solve?!

Any thoughts gratefully received!

Many thanks]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301982#Comment_301982 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301982#Comment_301982 Tue, 13 Jun 2023 11:02:07 +0100 Artiglio
At a gable end i’d not be too worried so long as the edge is fairly square and i was using nigh on half a slate, it’s pretty obvious if things don’t look right, if you have concerns you could fit much wider soakers in code 3, which would probably be easier than using the thicker slates you’ve found. This does assume that the roof is not very exposed / subject to extreme weather.

If it were at a verge , i’d be trying to find slate and halves.]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301988#Comment_301988 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301988#Comment_301988 Tue, 13 Jun 2023 11:48:31 +0100 fostertom Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301990#Comment_301990 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301990#Comment_301990 Tue, 13 Jun 2023 12:31:44 +0100 Mike1
As Tom suggests, buy new if necessary - they will blend in after a few years.]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301993#Comment_301993 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=301993#Comment_301993 Tue, 13 Jun 2023 12:38:03 +0100 revor If buying bigger slates to cut down make sure the "grain" runs the way you want. A bigger slate could be cheaper than slate plus 1/2.]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302010#Comment_302010 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302010#Comment_302010 Thu, 15 Jun 2023 14:15:10 +0100 greenfinger
@Artiglio - "i’d not be too worried so long as the edge is fairly square and i was using nigh on half a slate"

The edge isn't square unfortunately. The wall itself bends like a banana, and being a stone wall it's not flat either (protruding stone)... Perhaps worse still, it won't be anywhere near half a slate. It's pretty much thin slivers of slate. I will go up now though and double check/take measurements, as it's a while since I've been up there to look.

@Artiglio - "if you have concerns you could fit much wider soakers in code 3"

Wider soakers is something I had been thinking beforehand as well, just to go the full belts and braces approach. So I guess without slate and a halfs, that becomes even more important. I was planning to use either 225mm or 240mm lead, with 75mm upstands, leaving 150mm or 165mm wide pieces on the slates horizontally. Would that be wide enough do you think?

@Artiglio - "This does assume that the roof is not very exposed / subject to extreme weather."

The weather can be quite extreme where we are, but luckily it tends to come from the West and this gable end is East facing as quite shielded.

@fostertom - "What's wrong with new ones, apart from cost(?)."

Tbh, I just hadn't thought of that as an option. But now that you've mentioned it and I've looked into it, it would definitely be the cot putting me off! The backside has 20x12 slates. I've found 20x18 (450x500mm) and the cheapest I've found is around £25 per slate! I'd be needing around 10. Seems that's the largest they do, so that would still leave me without slate and halfs for the front, which need to be 24x20 or thereabouts. I didn't spend a long time looking, so they might exist. But didn't find any on first look, and live in fear of what the price of those bessies would be!

@Mike1 - "One company I worked for did a lot of re-roofing, and slate and a halfs were always mandatory to ensure water-tightness."

Was that using new or reclaimed? I've been asking about, and tend to get a chuckle when I ask for reclaimed slate and a halfs in the sizes I need. Most say not a chance in hell, and some expand that they never used slate and a half back in the day, which is why they don't exist in the reclaimed world.

@revor - "A bigger slate could be cheaper than slate plus 1/2."

It certainly seems that way. The only problem being as I said in the OP - that huge slates tend to be a lot thicker.



I had another thread recently in which I asked about doing the flashing in Z shape, which horizontals over the slates. It wasn't a popular choice. But if I can't get any slate and a halfs, would that not help as an additional layer of protection to lessen the amount of water reaching the soakers in the first place? That coupled with the wider soakers as discussed above?

Here's a link to that thread for future reference:

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17853&page=1#Item_23

Thanks again]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302012#Comment_302012 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302012#Comment_302012 Fri, 16 Jun 2023 06:59:23 +0100 cjard Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302013#Comment_302013 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302013#Comment_302013 Fri, 16 Jun 2023 11:53:42 +0100 Mike1 Posted By: greenfinger@Mike1 - "One company I worked for did a lot of re-roofing, and slate and a halfs were always mandatory to ensure water-tightness."

Was that using new or reclaimed?More reclaimed than new, but there are no doubt geographical variations in availability.]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302025#Comment_302025 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302025#Comment_302025 Sun, 18 Jun 2023 10:42:52 +0100 chrisinbrighton Showing how slates are split in a Cornish slate mine...made me think i could split my own!]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302144#Comment_302144 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302144#Comment_302144 Sun, 25 Jun 2023 16:27:59 +0100 greenfinger
I was thinking somewhere around the 100mm - 150mm mark. But having re-read the above, and looked into it some more, I'm wondering if perhaps scrapping that idea and sticking to just having the vertical flashing will suffice.


On a more general note, I think I may have mostly found what I need. I can get some slate and a halfs for the back of the house where the slates are a bit smaller. And I will try to cut the slates to roughly follow the contours of the wall.

For the front, I have now measured up... Using what I can get, in the worst case scenario the slate will stop an inch short, so leave an inch gap (maximum) between the side of the slate and the wall. ***Is this acceptable or an absolute no no?*** To help mitigate, I plan to use soakers with a 165mm width across the tops of the slates

Many thanks]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302246#Comment_302246 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302246#Comment_302246 Sun, 02 Jul 2023 14:33:45 +0100 greenfinger
The main question is - is it ok to have a one inch gap between the side of the slates and the abutment wall?   Soakers will have a width of 165mm.

Many thanks]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302247#Comment_302247 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302247#Comment_302247 Sun, 02 Jul 2023 18:17:50 +0100 Mike1 Posted By: greenfingeris it ok to have a one inch gap between the side of the slates and the abutment wall?I think that would provide adequate support, though ideally you'd space several of the adjoining slates to spread out the gap, unless the gaps between slates are already excessively wide.

However I'd also increase the width of the lead by 25mm to ensure adequate coverage - so a minimum of 200mm wide (125 on the slope + 75 up the abutment) instead of the usual 175mm.

Don't forget to carry the underfelt up the abutment, below the soakers.]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302248#Comment_302248 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302248#Comment_302248 Mon, 03 Jul 2023 07:04:33 +0100 cjard
Yes. Whether your gap was one inch or one millimetre, water will still end up dripping off the edge of the slate and onto the soaker below and end up being discharged onto the face of the next slate down

The smaller the gap is the more large wind-blown debris will be inhibited from coming to rest on the soaker, but that's about all I can think of for differences

"Soakers will have a width of 165mm"

Is that the total width before it's folded or the width that doesn't run up the abutment?

Spacing out several adjacent sites is a good call, though it might become visible if your slates are regularly sized- the break in the visual regularity may not bother you, of course..]]> Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302282#Comment_302282 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302282#Comment_302282 Tue, 04 Jul 2023 14:08:44 +0100 greenfinger
The issue with spacing out adjoining slates is that the plan was just to re-do the leadwork. As such I'm planning to strip a couple rows vertically. Stripping back more rows - to increase gaps enough to add up to what's required at the wall - would make it a much bigger job, which I'd really prefer not to.

Yes, sorry - I should have been clearer RE the lead for the soakers. I was proposing to get 240mm width lead, so 75mm upstand and 165mm on the slope.


Posted By: Mike1
Don't forget to carry the underfelt up the abutment, below the soakers.

    Thank you. Yes, this was part of the plan but appreciate the reminder! Would you come up the wall with the felt the same amount as the soaker (75mm)?


    Posted By: cjardThe smaller the gap is the more large wind-blown debris will be inhibited from coming to rest on the soaker, but that's about all I can think of for differences

    Hmm... Interesting to note. We live in a wooded area with plenty of leaves, pine needles, and debris about! I guess I'll just have to add it to the maintenance list to keep an eye on it and brush it down as and when....


    Thanks again :bigsmile:]]>     Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302289#Comment_302289 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302289#Comment_302289 Tue, 04 Jul 2023 20:17:11 +0100 Mike1 Posted By: greenfingerStripping back more rows would make it a much bigger job, which I'd really prefer not to.It's not vital - go ahead.

    Posted By: greenfingerI was proposing to get 240mm width lead, so 75mm upstand and 165mm on the slope.
    Sounds good.

    Posted By: greenfingerWould you come up the wall with the felt the same amount as the soaker (75mm)?
    Yes :)]]>     Don't use slate and a halves? Or use them but with thicker slates? http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302362#Comment_302362 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=17868&Focus=302362#Comment_302362 Sun, 09 Jul 2023 12:04:10 +0100 greenfinger