Should Hessian be nailed into external lime render scratch-coat? (and other questions)?

Discussion in 'Builders' Talk' started by Ollie (Croydon), Nov 25, 2021 at 1:17 AM.

  1. Ollie (Croydon)

    Ollie (Croydon) New Member

    We have some builders currently half-way through lime rendering for us. They've finished scratch coat ... but:

    -> I think without wetting bricks first
    -> have nailed hessian to this overnight (into the brick) until temperature consistently back to 5'c from Monday onwards

    What impact is this nailing in of Hessian likely to have on the scratch coat and overall rendering?

    What is likely impact of not wetting bricks first too? (fyi bricks are fairly porous/spooled due to a) old cracked cement render allowing moisture in /freezing and b) us getting that cement render removed)

    And what should we ask them to do? I'm thinking:

    -> remove nails
    -> fill in holes with fresh lime render
    -> drape hessian from roof downwards, keeping 1-2 inches away from the lime render
    -> drape plastic sheeting from higher on roof to keep area waterproof

    Any advice very welcome.

    (As background: we've had to stop these builders using PVA ("to help render stick"), Waterproofer ("to make mortar more workable") and Sika portland cement WinterMix ("to protect from frost"), so we're aware they're not experienced in lime.)
  2. jonathanc

    jonathanc Screwfix Select

    I wouldn’t worry about a few nail holes in scratch coat nor the hessian. It’s protecting the mortar from frost but allowing it to dry (or cure)

    bit late now but it would have been good to look at external insulation with render over it. Given the drive to make homes energy efficient it is something that is going to be on the cards

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