Home Forums General Discussion Building paper – purposes and problems

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    Sarah Grant

    Hello all,

    I’m wondering if someone can give me some guidance on the purpose/function of building paper and common problems? I’ve come across a couple of houses now with ripped (dry – no evidence of moisture) building paper under the roof and wonder what effect this has (if any) on the buildings performance?

    Is there anything in particular I should be on the lookout for (moisture is a given)?

    Thanks in advance,

    Ian McChesney

    Hi Sarah
    Attached is an article from Build magazine from a few years ago about roof underlay. BRANZ has further information that might be helpful as well.

    As the article suggests, underlay has multiple purposes – providing a second line of defence against any water leak from the roof and a collector/channel for condensation, reducing draftiness, and reducing ingress of dust/debris.

    Houses vary in being prone to roofing condensation, draftiness etc. So ripped underlay may not present any immediate issues in some houses. In others it might result in any leakage or condensation being channelled into the ceiling space rather than out to the guttering, and increase ceiling cavity draftiness, debris etc.


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    Sarah Grant

    Oarsome! 😉

    Thanks Ian!

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