Rendering over painted backgrounds

Backgrounds covered with paint result in a weak interface which isn't suitable for rendering directly onto. More importantly, rendering over paint is not in-keeping with good building practice – delamination, crazing and cracking are highly likely outcomes.

You will need to first remove the paint before prepping the surface and finally applying the new render. Alternatively, you may wish to apply a decorative finish, instead.

Step-by-step guide

  1. Remove paint

    Firstly, the paint will need removing by either sand blasting, grit blasting, or scabbling. Do not use chemicals.

    Note: It is important to ensure that all paint has been fully removed before proceeding to the next step.

  2. Clean surface

    It is important all dirt and organic growth is fully removed and cleaned as this can create a weak intermediate layer and affect the performance of the new render.

    Larger pieces of dirt and organic growth may be removed with a soft brush. Following this, a render biocide cleaner such as weber CL150 must be used to kill spores and prevent further growth.

    See our guide on using weber CL150 to find out how to do this.

  3. Apply primer

    Now the substrate is clean, prime with weber PR310 using a brush, roller or spray and allow to dry for 24 hours – drying time may vary depending on weather conditions.

    For product details or a more detailed application tutorial, please visit the weber PR310 product page.

  4. Apply new render

    Apply choice of new render and finish as desired, bearing in mind that the entire render system must not exceed a total thickness of 25mm.

    We recommend using a through-colour monocouche render:

    If preferred, you could instead use a base coat render such as weberend OCR and then add a decorative finish.

Contact us

If you have any questions about rendering over painted backgrounds, our technical team is here to help.

Our technical team are available 8:30am until 5:00pm, Monday to Friday.

    Click Compare to help you choose the right product for your project, if you need further assistance please email technical@netweber.co.uk

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