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Roof "revision" ? - Canal tuiles... What to expect and aim for?


joidevie
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I was hoping for some additional things to consider before our macon comes by this evening to discuss a 'revision' of our Canal Tuile roof.. Previous 'chats' with him have discussed bits and pieces, but I now want a clear idea of what to get him to do.

It's reasonably water tight but pretty old, and before plaster boarding the inside the loft, we want to get someone up there to clean, re-arrange, replace tiles etc so we have our best chance of no leaks. We've budgeted about a week's work for someone, and as many new tiles as they might need, and it's about 100 m/2 of roof (taking into account the roof pitch).

The chevrons running downwards are all good, and currently the tiles sit directly in the gap, and are mortared in with a crumbling chalk based mix. No litteaux or planks running cross ways.

What should the macon be recommending? Lifting every single tile, cleaning and replacing? Should that bottom layer be mortared in again, or should it just sit with gravity in action? Should any 'cross slats' (litteaux) be added? I presume the main central ridge should at least be mortared in.. Is there a good herbicide to consider applying to deter weeds?

Our plan later was to then attach OSB 3 underneath the chevrons (from inside the loft), then some battens, insulation & placo.. But my concern is spotting any later leaks, and any water running through the tiles will naturally accumulate at the point where the OSB and beams meet.

I suppose, if each tile is actually lifted, the OSB could go on top of the chevrons, but this would all amount to an almost re-roof, with scaffolding, much higher costs etc. Which is a bit more than we perhaps wanted for now..

Any thoughts on an effective and low to medium budget 'revision'?

Many thanks..

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Your roof repair is a very elasticated piece of string. Noone seems to really know what is wrong with it, what needs repairing and how far to go. Are the tiles old? Are the bottom tiles flat or round? When was the roof last replaced? It seems that you could go from replacing a few tiles to replacing the whole roof and that you are in the hands of the roofer for this.

How did you choose him, has he worked locally before, is he a registered artisan, how many quotes are you getting? Have you made it clear to him that you want it repaired to last a few years until you do the whole job? Can the job be donw before winter?

Questions, questions, but they all need to have satisfactory answers before you can proceed.

If the tiles are cemented in and not hooked over horitontal wooden strips, then I suspect the roof may be quite a bit older than you think, but I could be wrong. Either that or it is an amateur job, perhaps.

One could go on!
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We completely replaced our roof, apart from most of the

chevrons, a couple of years ago, as some of the large purlins supporting the chevrons were rotten where they were set in the walls.

One section was constructed as you describe, closely spaced chevrons with the lower canal tiles bridging the gap and held in place with plaster. It was apparently built in the early part of the last century, possibly in the 1920's or '30's.

Although it didn't seem to leak, the old tiles were almost certainly porous, and since we were about to replace about 2/3 of the total area with new mechanical canal tiles (fixed on battens over OSB and a membrane), we decided to replace the entire roof. It was quite expensive, but should outlast us [:)]

The total, including replacing a quarter of the purlins and any bad rafters, was just on 31,000€ for 260 sq. metres of roof.

If your tiles are quite old there is a good chance that they may break when removed, and that it may not be possible to find new tiles with the same dimensions.

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When we had our roof done - 10 years ago now - we were told in no uncertain terms that to retain as many of the existing tiles as possible would mean:

1. a very high cost - every tile would need to be inspected, assessed and if deemed Ok, carefully lifted down and stacked for reuse. Matching tiles would need to then be sourced and would probably be more expensive than brand new ones.

2. There would ne no insurance on the old tiles, since only a visual assessment could be made and it would be valid on the day of inspection only. For that read, there is no insurance at all except for grossly negligent work.

We replaced the whole lot, and having seen the state of the removed tiles, it was a good decision.
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Many thanks for all of the helpful responses..

For the meantime, we have decided to invest in a few day's labour and 150 or so new tiles (a new 'patinée Midi' style which look great) to replace any degraded/cracked/broken tiles, along with a good 'lift & sweep' and rearrangement etc. Probably around €1,200 all in once all the bits 'n bobs are included..

The basics are all pretty decent in truth, and access to the chevrons and beams is an easy reach, and I'll Xlophene everything, and I even bagged a couple of large tins of water based exterior wood varnish which I'll spray onto susceptible timber.. It would be so easy to over spend on these sorts of things, and with regular 'tidying & cleaning' of the tiles, we hope that all will be well for the meantime..

Thanks again.

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Hi Joidevie

I had the same problem and done the same as you you propose if I had wind in the wrong direction and it rained, water would blow under the tiles and enter as drips always in strange places, answer, seal the underneath of the roof joists, new problem, as the gap to beam could not be sealed i ended up with drips coming down where the boards met the beams, this did allow a better control of the drips as i could catch them with a bucket. my answer in the end was to remove every tile and and lay a breathable membrane onto the wood, secured with the odd staple, then re fitted the tiles on top, now I have no problem as any water getting under the tiles passes down the membrane and into the gutter and not into the bedroom, as the membrane is around 1 Mtr wide I removed the 1st mtr high amount of tiles from bottom of roof and stored them off the roof, then laid and fitted the membrane, the next Mtr of tiles above were removed and placed straight onto the membrane below them thus leaving a new Mtr high space to fit the next line of membrane and continued this up the roof simply refitting the removed tiles onto the new run of membrane a Mtr run at a time continued this to the ridge then only had to bring the first line of tiles stored, back up to the roof for the last run, it was a bit easier then it sounds, hope it makes sense and not made your brain explode.

Dave
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You can never be sure with canal tiles (they can look fine from the ground but just overlap and let water through with worrying consequences). C

Canal tiles "should" all be held with special hooks to prevent them slipping down.

When we bought our house, the roof was leaking as most of us have experienced. After some research, we went for sheets of Eternit "flammee" www.eternit.fr which are screwed into your timber, ensuring the roofremains watertight for many many years to come.

The roofer then put the original covering canal tiles on top with those hooks (they come in 3 lengths).

This also allows the weight on the roof timber to be halved, can't be bad.

Our roof now looks as if it had never been touched.

I am so happy with the result that I am going to re-roof both our little open barns myself (the roofer, now retired has agreed to be my consultant for that job).
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