A question for any experienced roofers... We had the entire roof tiled with Spanish Duquesa slate tiles just over a year ago, and have had at least half a dozen slip or slide off completely since then, several fairly soon after completion and the rest one by one during the year. So the question is, does this sound acceptable / reasonable / to be expected, and if not is the most likely reason to be poor quality slate, or poor quality fitting? Many thanks for any and all informed feedback.
Fixed correctly, slates shouldn't move or come loose, now't wrong with slates,poor workmanship, in fixing, batten spacing & batten size. Cembrit stipulate slates must be laid in accordance with the Code of Practice for Slating and Tiling, BS 5534: 2014, and the Code of Practice for Workmanship on Building Sites – Slating and Tiling, BS 8000: Part 6: 2013. How were they fixed, Cembrit recommend slates should be twice centre-nailed to horizontal battens which should 50x25mm, nails should be copper,or other suitable nail, & penetrate into the batten by a minimum of 15mm. As to fixing hole I have always prefer to drill them,(slower) but, least chance of damage to the slate, then punching hole through. There also the hook fixing method.
KIAB - thanks for the response, that's sort of what I was expecting, but as I know next to nothing about roofing I just need some independent experience so that I can go back to the roofer with some kind of confidence or assurance that it is definitely down to poor workmanship, as I'm almost certain he'll try to blame the materials! I don't imagine he would have followed those codes of practice, but did seem competent and experienced, and appeared to fix them as you stated (no way of measuring nail penetration though). The slates appeared to have holes pre-drilled, and of the couple that have come away and not smashed to pieces, it does look like they have split across from one hole to the other, which is why I'm in two minds about the cause. I've attached a photo of one of the slopes to give an example of the work mid way through. Thanks again, any other informed advice from anyone would be welcome!
Jitender - yes, it was a roofing contractor, but not the first choice of the overall works contractor. If you were going to suggest he should come back to repair / replace, that is what we're about to do, but I'd like to have some 'ammunition' before we have those conversations with him...!
Looking at the pic, it seem they have done a good job, even using copper nails to stop them rusting, can't see how there would be problems looking at the work in the pic.
The roofing works looks good, roofer has used copper nails. The slates seem very thick compared to some welsh slates, and has use double tile to the gable end. Doesn't look like they have installed a felt support tray for the gutter. The only way to reinstate the loose tiles is by hook or straps now. Is there a possibility that the roofer clambered onto the roof after the job and could have possibly broke some slates during the process 9i.e when the (ridge tile were fitted), does happen -and is most likely the cause.
JoHo, any idea if the roofer left a 'minion' to do the donkey work? All it needs is a heavy-handed person who doesn't know when to stop 'ammering... Too many clunks and the slate is fractured along that batten-line, betwixt t'two 'oles. Whatever the cause, it is not normal and I'd say not acceptable. At all. I mean, how many years did your last roof covering last without any broken slates/tiles?! The onus is on the roofer to sort it. End of. If the cause turns out to be down to faulty slates (I doubt it...) then it's for him to prove that and get recompense from the supplier. If he doesn't play ball, then you need to tackle this the correct way - recorded delivery letters, etc. He needs to be told he sorts it (with a specified time interval for him to respond - say 2 weeks) or else you'll get someone else to repair the roof and sue them for the total cost. Obviously be reasonable in your dealings - "it is with regret..." - but the bottom line is that it's not normal and is unacceptable. The roofer - who I presume bought the tiles and fitted them? - is liable. So he needs to understand from your conversations that you know this and will ultimately hold him accountable. If, however, you bought the slates and he chust fitted them, you're stuffed...
Thanks for those views, but again brings me back to the initial question of would you expect a small percentage of tile failure, or would it definitely be due to some form of incorrect fixing? I probably should mention that this was quite a big job, I can't remember the exact figures but I think the slates were in the thousands (?), so would half a dozen slipping be the norm? Don't know if it's pertinent but most seem to be in the bottom row, directly above the guttering, or one or two rows above. Attached a pic to show the remains of one of the slipped tiles, see what I mean about the split between the holes? Faulty tile or the result of damage whilst fixing?
Jitender - ridge is mortar and original (Victorian?) ridge tiles replaced? Devil's - Yes, minions were left on many occasions, so this is my primary suspicion - but again, just trying to get a gauge on whether there is as much chance of faulty / failing tiles, which judging by your comments, there isn't! The tiles were bought by the overall works contractor (there was a lot of other work done at the same time), and it is he who we are in contact with. I'm fairly confident with our position, but as I say it would be good to be able to stand firm with some conviction just in case either tries to wriggle!
Slates will sometimes delaminate if you puch holes through, that is why I prefer to dril the fixing holes. Nails could be too short, considering thickness of slates.
I have done some roofing work, only concrete tiles. The first row of tiles (half broken) do not look as though they have been nailed into the battens, unless they were re drilled and secured.
BS 5534: 2014 Only came mandatory form Feb 2015, although many roofers worked upto the standard up until that date. I would have expected the ridge tiles to be dry fixed rather than mortar alone, as it is now a requirement to be either mechanically fixed or with mortar and mechanical fixing. Are the ridges like this That's a fair bit of tiling, so the breakages is very minimal.
I tested Chinese slates at a local testing facility as the slates had blown back and snapped. I got the data sheet, had them tested against their tolerances and they were compliant. Was due to the nails fixing them and high prevailing winds - copper should have been used. The test cost about 60 quid.
My money is still on them being blattered too much during fitting - the nail holes are chust above the top edge of the lower tile so the stress line will be focused along there. But - sadly - good luck trying to prove it... All I can hope is that the original roofer will replace them FOC or charge only a minimal sum. Nice looking slates, tho'...
KIAB - nails were evidently '65mm copper clout'. Just out of curiosity, can anyone tell me why they used extra strips of (untreated?) batten on the bottom two rows? Seems to be a feature on every slope...
BMC2000 - these slates are Spanish, and are supposed to be very high quality (Cembrit Duquesa), hence my query as to whether anyone has any experience of failures of this specific tile; is it a known issue with them? I did wonder if recent strong winds may have played a part, as being a three storey building the roof is maybe more exposed, but surely if fitted correctly they should be secure enough? Jitender - this is an image of a large part of the roof, and the ridge tiles in place, if it helps identify the fixing method - although ridge tiles haven't been an issue. Hopefully also gives an idea of the scale of the job - maybe half a dozen slipped tiles are to be expected...?
Devil's - Currently there isn't an issue with the roofer coming to repair / replace FOC (once we can pin him down to a date...!), so this is really just a pre-emptive info gathering exercise just in case things get awkward at any point. Particularly if this becomes an ongoing issue - whether to expect a regular cascade of tiles, and if so how best to convince him that it really is his problem and he needs to sort it indefinitely?
When I did a re-roof a few years back, I used a dry fixing for the ridges which didn't use any mortar and this provide ventilation 10mm air gap. I'm sure there are products available on the market for your type of tile. Funnily enough I have a picture of a church roof which was probably done about 20 years ago, using fibre cement tiles, and have the same ridges as yours. i will be going over sometime this week so will be able to get a better picture of it, but the joints between each ridge are very minimal and don't seem to be held with mortar.
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