The ground floor ingress and façade had been rendered in a modern Portland cement render and painted with an acrylic paint system: we decided to recoat this part of the façade in acrylic paint. For the first floor and parapet, we decided to preserve the various existing renders and use mineral materials without any plastic additives to avoid the same damages reappearing again in a few years.
This is the typical appearance of a degraded paint system based on synthetic polymers. These paints are incompatible with lime render and contribute to the early deterioration of lime rendered facades.
Paint over shrinkage cracks in lime render: a set of differential physical characteristics causes the synthetic paint coating to fail. Shrinkage cracks arise by applying render under the wrong weather conditions.
Water damage on the profiled cornices led to the complete disintegration of the render.
We removed the paint with a paint stripper and hot pressurised water. This procedure exposes the various layers of paint applied to the façade and renders the leftover paint porous enough to accept the new material used for its renovation.
Paint removal is a laboursome step in the preparation phase, but necessary to optimise the surface of historic buildings before applying the correct materials to guarantee a durable and respectful renovation.
The original render is in fair condition. The original coating, applied over the freshly applied render, consisted of a lime wash tinted with ochre oxides.
Interesting fact: the perimeters of the various façade elements and the cornices were executed in a different render, with a higher content of hydraulic components – a means to accelerate drying times and facilitate the execution of the work.
Here we see the various layers of the original render system, showing on top the leftovers of the modern paint (yellow topcoat and white primer) and the tinted, reddish lime wash on the red top coat render. Limewash over render was always considered a sacrificial coat to be reapplied regularly, thus protecting the underlying render system effectively, making up the much more costly and, therefore, more valuable façade element.
Interesting detail: the original yellow render next to two repair patches from different renovations. Although not ideal, we left those patches in place to keep the costs down.
All repair work was executed in pure hydraulic lime render, with coarse sand for the scratch coat, and graded fine sands for the top coat.
Scratch coat
Cornice repair with the same render based on hydraulic lime
Finished cornice repair with smoothly troweled in top coat
Another section of the final repair work of the cornice
We rendered over the flat sections of the façade with a very fine render mix, also based on pure hydraulic lime as a binder. This is very satisfying work and guarantees maximum compatibility between old and new renders, thus facilitating graceful ageing and - this is an important detail: straightforward future maintenance work.
Lime render surface ready to be coated. Maximum compatibility and durability are achieved by using purely mineral coating systems, which are lime wash or silicate paints.
Render has three primary functions: 1) protect the brickwork, 2) add decorative surface structure, 3) regulate water content and evaporation. "Natural" render and coating systems facilitate the last two functions without compromising the first and most important one.
The following pictures illustrate a few details of the restoration work and the beauty of the lime render.
When applied during the warmer season, lime render must be protected from drying too quickly and kept moist over an extended period - planning is essential.
Moist render must be protected from direct sun and wind - premature drying would stop the lime from curing correctly and lead to a shortened durability of the renovation.
Due to harsh weather conditions (leading up to summer), we abstained from coating the restored render with lime wash. We decided instead to paint the restored façade of the first floor with pure mineral paint. The ground floor was coated with Porter's stone paint, a flat acrylic paint.
Lime Render Facade Restoration
Location: Middle Park
Building Type: Heritage, residential
Budget: $25’000
This Melbourne terraced house, heavily altered by previous renovations, was up for a fresh façade. The project’s goal was to optimise technically
the compatibility between the existing materials and the materials we chose for the
restoration.
Since the ground floor ingress and façade have recently been renovated and rendered in a modern cement render and painted with an acrylic paint system, we decided to focus our restoration work on the first floor and recoat the ground floor of the façade in acrylic paint.
For the first floor and parapet, we decided to preserve the various existing renders and use mineral materials without any plastic additives to avoid the same damages reappearing again in a few years.
For the render repair and skimming, we used three different on-site lime mortar mixes based on NHL (Natural Hydraulic Lime) and a variety of graded sands – free of any sealing or bonding agents. We used a mineral paint free from any polymer additives for the coating.
