I just bought a house which had an extension done 12 years ago. I am about to do some work in this area and want to understand what has been done before. Below is a screen shot of the bits of the planning drawings relating to the flat roof construction.

Planning drawings re flat roof construction

  1. What does this say? (it is hard to scribe something when you don't fully understand it )




on 70 mm pearldeck,

175x30 mm joists

on 400 mm centers

  1. What is a pearldeck?
  2. Is this a warm or cold roof?
  3. Does this have sufficient insulation properties or would you recommend I add more?
  4. If yes, can I do this internally without causing condensation issues?

on [10?]mm PEARLDECK ([.025/.023])
ON @@@@@ SC3 Joists

@@ RRING [PIECES?] [10?/TO?] @@@ 1-30

CP144 is a standards document describing roofing requirements. (It's been superseded.)

Based on some cursory research, it doesn't looks like Pearldeck comes in 10mm thicknesses, so I'm not sure what that number might be.

SC3 is a European strength rating for joists that has been replaced by a different rating system. (According to the link, SC3 is roughly equivalent to C16)

I'd bet that the last line is "100 CENTRES" with 100 being cm, which seems to be a common spacing for joists.

Pearldeck is hard to find, but based on these two sources:

http://www.woodgreentimber.com/Roofing-Materials-Wood-Green-Potters-Bar.php http://www.euroken.net/supplies/products.html

It looks like it's an insulation board for roofing.

As to whether or not it's a good roof, cold, hot, or anything else, I have absolutely no idea, and it will largely depend on your local climate. Maybe an expert can add something to this answer, or maybe my translation will let you ask someone you know.

Lastly, not only am I not a professional, but I'm also American (I'm not familiar with common European building measurements/practices), so any or all of this might be completely wrong. This is all based on deduction and Google ;-) So feel free to edit whatever is obviously wrong.

I hope that helps!

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  • 5
    it's probably 70 mm pearldeck, 175x30 mm joists on 400 mm centers. – longneck Feb 26 '14 at 16:27
  • 1
    70mm insulation board alone is a little scarce for roof insulation, but might there be more insulation in the roof structure? There's no way to know if this is a hot or cold roof from the description, it's what's below and how it's vented that would determine that. Any added insulation that's not waterproof needs a vapour barrier to prevent condensation from forming in the insulation. – bcworkz Feb 26 '14 at 17:57
  • bcworkz, it does not have any insulation in the void above he ceiling (if that is what you are referring to?) – Joe U Feb 27 '14 at 21:49

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