Semi detached 1940's house - Re-roofing 1 house only (slate)

Discussion in 'Builders' Talk' started by BMC2000, Oct 7, 2015.

  1. BMC2000

    BMC2000 Screwfix Select

    Hi there

    I have 16x40mm slating laths on 110mm rafters and a natural slate covering - all as original with no sarking felt.

    I am undertaking a loft conversion and am using it as an opportunity to strip off and add a breathable membrane (Kingspan Nilvent).

    As my roof runs into my neighbours roof, I didn't want to push the height up by using 25mm laths, what is the opinion of the forum on this? Is it best to keep the original sizing or would you go for +9mm and risk an ugly interface detail or worse, would this put stress on the last line of slate toothed in to the neighbours.

    The neighbour doesn't want to do her roof at the same time unfortunately.

    Als - nails wise, if using the 16mm lath I was thinking a 60mm annular nail (stainless) and for the slate copper 38x3.35mm annular nail.

    All advice welcomed!
     
  2. chippie244

    chippie244 Super Member

    If 16mm lath has lasted 75 years you're probably fine using it again.
     
  3. Jitender

    Jitender Screwfix Select

    I don't think 9 mm is going to make much difference.

    In an older style house the rafters are more likely to sag in places anyway, and this is what adds character to an older style roof.

    When you re roof pull a string line perpendicular to the rafters and you will see that they don't line up.

    You will have to replace the batten thickness with the current regs at time of re-roofing.

    You could overcome the discrepancy between your roof and your neighbours' by carefully removing the last nailed in battens and packing it out by 9mm, so the slates will blend in more smoothly. I would recommend using stainless steel screws when refitting the battens/laths.
     
  4. chippie244

    chippie244 Super Member

    I've helped on a few re-roofs and we've never used S/S screws.
     
  5. Jitender

    Jitender Screwfix Select

    For the main re-roof annular galvanized nails would be ok, you could use 63mm paslodes.

    For the stainless steel screw I am only referring to the neighbours batten which will need securing once it has been packed up by the desired 9mm, if done carefully you could use the same hole, and when/if the neighbor does decide to re roof in future then removal would be a lot easier.

    Remember for securing the slates you will need to use a smaller nail, otherwise it could damage the underfelt.
     
    BMC2000 likes this.
  6. chippie244

    chippie244 Super Member

  7. BMC2000

    BMC2000 Screwfix Select

    Thanks guys, I appreciate the input.

    Jitender, by packing out the neighbours batten by 9mm I'm I just moving the bump, and not solving the difference? From your experience does the difference in height look negligible?

    Finally, although I spec'd 25mm on the Building Control drawings, what part of the regs say battens had to be 25mm minimum?

    All I would need was an over eager inspector if I did the 16mm option for a world of pain!
     
  8. chippie244

    chippie244 Super Member

    It would be 9mm difference over 400mm.
     
    BMC2000 likes this.
  9. BMC2000

    BMC2000 Screwfix Select

    A good point well made, although I know the 16mm will do, I reckon I'll go 25mm I reckon, will try the packing out advice too.
     
  10. chippie244

    chippie244 Super Member

    If you don't go for the packing you would have to plane the last 400mm down from 25mm to 16mm which would appear not to be in regs.
     
  11. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Or plane down the last 800 or 1200mm to give a more gradual decline.

    Would you be keeping 16mm at the top, to keep the ridge tiles even?

    Mr. HandyAndy - Really
     
  12. BMC2000

    BMC2000 Screwfix Select

    That was my other knock on concern though I was thinking with it being held in with mortar I'd have more scope to play around with
     
  13. BMC2000

    BMC2000 Screwfix Select

    The more you try and make the 25mm work, the more you think of keeping it as is!
     
  14. chippie244

    chippie244 Super Member

    Just off the top of my head but you could rebate into the rafters by 9mm where the lath is to go or just do 9mm on the first rafter and then 4.5mm on the second, it will never show and your lath meets regs. Use a sharp chisel. There will be slight creases in your membrane.
     
  15. BMC2000

    BMC2000 Screwfix Select

  16. Jitender

    Jitender Screwfix Select

    Finally, although I spec'd 25mm on the Building Control drawings, what part of the regs say battens had to be 25mm minimum?

    This is a good guide to roof battens, it states that battens need to be minimum of 25mm thick, and come in 38mm or 50mm depth depending on the rafter spacing and roofing material used, but in using slate a 50mm depth batten has to be used whether the rafter spacing is betwwen 450 and 600mm. You will now see at the timbers merchants the battens are pinkish in colour.

    New regs introduced means that ridge tiles cannot solely be bedded on mortar, which has been the tradition method used. But now indicate that a mechanical fixing is used whether solely or in conjunction with mortar.
     

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