Falling render and bulging external insulation become a falling-object hazard over time and create liability for building management. Unsafe sections must be removed under control and the surface rebuilt, prioritising anywhere material could fall.
A crack in a facade is not just a cosmetic issue. Bulging insulation and loose render are a serious risk in buildings with pedestrian traffic below, and the building can be held liable for resulting damage.
Common causes
- Water ingress: water entering the facade collects behind the cladding and breaks down the adhesive.
- Thermal movement: day-night temperature differences drive expansion and contraction.
- Installation defects: insufficient adhesive or missing mechanical fixings.
- Ageing: the material reaching the end of its service life.
When it cannot wait
Work should not be postponed if any of the following apply:
- Material has been seen falling from the facade
- Large areas sound hollow under hand pressure
- There is visible separation at the parapet or soffit
- Balcony soffits have started to shed
The repair process
- The facade is worked on rope and hollow areas identified, usually by tapping.
- Loose sections are removed under control — the ground must be cordoned off at this stage.
- The substrate is prepared, insulation board renewed where needed and mechanically fixed.
- Render and finish are applied to match the existing facade.
Repair or full replacement?
If the hollow area is a small part of the facade, localised repair is both economical and sufficient. Where the problem is widespread, repeated local repairs cost more over time than full replacement. That assessment should be given honestly after the survey.
Frequently asked questions
Why does external insulation bulge?
The most common causes are water ingress behind the cladding, thermal movement from day-night temperature swings, insufficient adhesive or missing fixings during installation, and natural ageing.
What should be done if material is falling from the facade?
The work should not be postponed. Loose sections must be removed under control with the ground cordoned off, and the surface rebuilt. The building can be held liable for damage caused by falling material.