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Ridge tiles looose and chimney crown replacing

Discussion in 'Roofing and Guttering' started by echase, 10 Sep 2010.

  1. echase

    echase

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    After 25 years the ridge tiles on my roof are quite loose in places. They are a grey cement/concrete type. Some can be just picked up as the mortar no longer ‘sticks’ them on. The mortar looks like lime and is quite soft/eroded in places but none falls out in chunks even if I do lift a tile. They are only mortared at their ends and not all along the roof/ridge tile interface. Is that normal?

    I have scaffolding up for another job and only have a very short time left before it comes down, so I don’t really have time to remortar the whole run, nor the skill to do it well. So instead what about using a bitumen sealer paint to fill the mortared gaps between the ridge tiles. This will waterproof the mortar (limiting further erosion), stick the tiles to the mortar and stick the tiles to the roof tiles at their corners only. Also retains flexibility if not applied too thickly. I have some Aquaprufe water based emulsion bitumen I could use. It’s quite thin so will penetrate the joints well. Any drawback? How flexible does the joint need to be to allow for heat expansion, etc?

    I also have an unused chimney with metal flue pipe whose mortar with cement on top crown is completely broken up. Can I just use a premix concrete to replace this? I have read that 2:1 cement and pea gravel mix or 1:4 cement and sand is recommended so this premix is pretty close. I am not casting an overhanging cap. And what about bitumening over that too to limit water ingress? Not suitable for a working chimney.
     
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  3. echase

    echase

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    How UV proof is Aquaprufe? Do I need to sprinkle sand over it to reflect the sun?
     
  4. SASroofer

    SASroofer

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    :confused: I'd have them re-bedded tbh, any other way is just a bodge.
     
  5. echase

    echase

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    OK it’s a bodge but realistically there was no time to re-mortar them so a few more years would have gone by till they started crashing to the ground.

    The alternative argument runs like this. For thousands of years lime mortar has been used and it’s know it lasts decades at best (about 20 years on my house) before repointing is needed. Also cement mortar is used. We presumably now have better materials based on plastic (e.g. epoxy) or rubber, either as mortar substitutes or as protection over the lime or cement mortar.

    So it’s a low cost bodge to still use only conventional mortar, yet 99% of the building trade do so, as there are presumably alternatives that now achieve a longer lasting result. Using a higher cost and more reliable method would be well worth it on chimneys, ridge tiles and other hard to get to and exposed/high heat stress locations.
     
  6. chappers

    chappers

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    how come you don't have time, it's a couple of hours work to rebed the ridge, I suspect it will take at least that long to bodge it.

    Just because we aren't using the original method doesn't mean it's a bodge. Cement mortar is the accepted method and in this situation is far superior to lime mortar.
     
  7. SASroofer

    SASroofer

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    What he said, you're better off leaving them well alone than pugging them up with some mastic or gunk, nothing out there is better than sand/cement mortar and if done properly should last as long as the tiles on your roof will.
     
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