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If I have cement render inside or outside of my solid walls, should I strip it all off before insulating?
Cement renders and plasters are actually not that vapour impermeable when compared to limes and so assuming the external surface of the wall is in good order and not letting in any rain then there should be no need to remove an external cement render. In some cases the render is actually beneficial as it will prevent rain driven moisture from penetrating the walls, keeping the insulation drier.
Internally cement plasters are also not a problem as they can often provide a useful surface into which the insulation fixings can hold. Removing the cement plaster can also do a lot of damage to soft brick and stone and so we usually suggest it is left in place. However, any pink gypsum plaster should be removed as it can attract moisture and cause elevated moisture levels in the insulation, resulting in decay in wood fibre insulation or other natural fibre insulations.
We offer dynamic heat and moisture modelling as well as condensation risk analyses.
Back to Earth is a natural building material supplier. We're not your typical builders' merchant though and instead work closely with our clients during the planning, designing and building phases of projects.