External render onto Thermalite block

Discussion in 'Builders' Talk' started by Plumbcrazy, Mar 20, 2004.

  1. Plumbcrazy

    Plumbcrazy New Member

    Do you need to treat the block surface prior to smooth render to prevent the water being sucked out of the mix, or is a plastasizer and waterproofer in the mix adequate? I intend two coats, but don't want the first to crack by being sucked dry in seconds.
  2. Robbo

    Robbo New Member

    I think Thermalite do a product that you mix to a slurry and then scud on to blockwork to help with suction dont recall what it is called but do remember the fumes make you high, If you dont enjoy that get a gas mask.
    Incidentally it is not actually that good, use a hose pipe unless you have some one (ie. architect that says otherwise) better still use both, and a good bit of waterproofer in the scratch will hold back the finish .
    Why do you have Thermalite as opposed to Clinkers externally B.T.W.
  3. Plumbcrazy

    Plumbcrazy New Member

    Thanks will look into that with Thermalite. Thermalite outer skin because Mr Thermalite said it was fine for both inner and outer skin above DPC and better U-value, also light to handle and cut easy. Think I'll go without mask, could do with the high!
  4. Plumbcrazy

    Plumbcrazy New Member

    Thermalite hedge their bets somewhat on their finishes section. They do say that a suitable bonding agent could be applied prior to the render scratch coat. I've slapped a PVA solution to brickwork on internal walls prior to render, I GUESS that this situation is no different. Any thoughts anyone?
  5. Wattsy

    Wattsy New Member

    Course I was on recommended soaking the wall thoroughly and to use a weak mix such as 6:1 and waterproofer.Though there were differences of opinion between lecturers.Some said to use pva or a derivative of it (SBR) and a 5:1 mix.
  6. Robbo

    Robbo New Member

    In practical terms a good hoseing does the job, but it is not reccomended by either Thermalite or any engineer..architect..B.Inspector. But then what is usually practical and what your standard run of the mill architect has taken from some book and landed on you are invariably polls apart.
    Allways have your backing coat stronger than the finish and a good thick coat at that so the block wont show through the finish. plenty of waterproofer in the scratch as it will be better to sit all day supping tea waiting for it to take up and get it sponge finished perfect than it setting straight off the trowell me thinks.

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