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External Render Systems Marmorit/Sto/ Alsecco/K rend/Lime

Solid wall retrofit insulation: Render on insulation (insulated render)


  • Insulated render is usually applied as part of an overall refurbishment scheme.
  • Where external walls are poorly insulated.
  • Where external walls are deteriorating or are insufficiently weather tight, causing damp, draughts and heat loss.
  • Where wall cavities are bridged or blocked, making them unsuitable for cavity fill insulation.
  • The external appearance needs updating as part of a rehabilitation scheme for high-rise or system-built housing.
  • Installing internal lining insulation would be disruptive, would alter critical internal dimensions or make room sizes too small.
  • Greater thickness of insulation is required compared with what is usually achievable with internal linings


  • The design and installation of insulated render is a specialist job.
  • Though not always, insulated render systems usually come in the form of proprietary products. In these instances, standard details and construction methodology are determined by the system manufacturer.
  • The products are accredited by a third party such as the BBA or BRE for use in specific situations.
  • They are normally guaranteed when installed by the manufacturer’s approved contractors.
  • Though construction technique remains the same, systems differ through their use of components such as types of insulation or render finishes.

Cement rendering

This Is the application of a premixed layer of sand and cement to brick, cement, stone or mud brick. It is often textured, coloured or painted after application. It is generally used on exterior walls but can be used to feature an interior wall.
Depending on the ‘look’ required, rendering can be fine or coarse, textured or smooth, natural or coloured, pigmented or painted

Acrylic Rendering

There are also a wide variety of premixed renders for different situations. Some have a polymer additive to the traditional cement, lime and sand mix for enhanced water resistance, flexibility and adhesion.
Acrylic premixed renders have superior water resistance and strength. They can be used on a wider variety of surfaces; including concrete, cement blocks, and AAC concrete panelling. With the right preparation, they can be used on smoother surfaces like cement sheeting, new high tech polymer exterior cladding such as Uni-Base, and expanded Polystyrene. A few of these require activation with cement just prior to application.

Some of these premixed acrylic renders have a smoother complexion than traditional renders. There are also a wide variety of acrylic bound pigmented ‘designer’ finishing coats that can be applied over acrylic render. Depending upon the product, they can be rolled, trowelled or sponged on. A limited number can also be sprayed on. Various finishes, patterns and textures are possible such as sand, sandstone, marble, stone, stone chip, lime wash or clay like finishes. There are stipple, glistening finishes, and those with enhanced water resistance and anti fungal properties. Acrylic renders take only 2 days to dry and cure – much faster than the 28 days for traditional render.