What is a precast concrete sandwich facade?
A precast concrete sandwich facade (in Dutch sandwichgevel) is a prefabricated concrete facade element made up of three layers: an inner leaf, an insulation layer and an outer leaf. The three layers are cast in a single mould in the factory and tied together with anchors. On site, the complete element is lifted into place with a crane. In one operation you get a loadbearing wall, the insulation and the finished outer facade.
Build-up
- Inner leaf: the thickest part, often loadbearing. The floors rest on it.
- Insulation: usually PIR, EPS or XPS boards or mineral wool, in the thickness needed for the required Rc value.
- Outer leaf: a thinner concrete shell that takes the weather. The surface can be finished smooth, sandblasted, exposed aggregate, with a pattern or with cast-in brick slips.
- Anchors: connect the outer leaf to the inner leaf. They are made of stainless steel or glass-fibre-reinforced plastic. Plastic anchors cause fewer thermal bridges.
The outer leaf moves differently from the inner leaf as temperatures change. The anchors are therefore arranged so that the outer leaf can expand and contract without cracking.
Applications
- Series housing: terraced houses and flats, where many identical elements are needed.
- Non-residential buildings: offices, schools and commercial buildings.
- Fast construction: the facade is closed in a short time, so the fit-out can start sooner.
Advantages and disadvantages
Advantages: high dimensional accuracy, little work and waste on site, consistent quality and a short construction time.
Disadvantages: a crane is needed, the size of an element is limited by transport, and later alterations are difficult. An extra window or opening cannot be made without consulting a structural engineer, because the wall is often loadbearing and the anchors must not be damaged.
Points to watch
- The joints between the elements must be properly sealed and maintained; this is where most leaks occur.
- Do not fix anything heavy to the outer leaf alone without advice from the supplier.
Related terms
- Cavity wall insulation
- Thermal bridge
- Facade panels
- Stainless steel
- Sandwich panel
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