Restoration of Portland Stone Floors at Leinster House

By Published On: November 4th, 2021
Leinster House Main Foyer Portland Stone Floor

Restoration of Historic Portland and Limestone floors

Client: OPW

Architect: OPW

Main Contractor: Duggan Bros

As part of the major restoration and conservation works carried out at Leinster House, we were honoured to be awarded the contract to restore the historic Portland Stone and Limestone floors and stairways throughout. The overall conservation strategy for Leinster House placed the emphasis on repair and conservation of the historic fabric of the building rather than replacement. We adhered strongly to this strategy when restoring the stone floors, carried out repairs to stones wherever possible and only replaced with new stone when absolutely necessary.

Restoring 18th Century Workmanship

The stone floors are original to the building dating back back to the mid-18th century. If stones could talk right? The intricate design in the main Foyer is a regal checker pattern of octagonal white Portland stone with smaller black stone inserts. Borders and thresholds are highlighted by using a combination of rectangular and triangular patterns.

The floors have undergone some change, covering up and abuse over their 300-year history, however, all things considered, they were in pretty good condition. We were very confident we could bring the floors back to close to their original state and ensure they were functional for generations to come.

Removing layers of glue, paint, polish and concrete

Some stones in the main foyer had been replaced at some stage with black limestone. Extensive areas of the main foyer and stairs were covered in an orange/brown carpet residue which had seeped deep into the stone causing brown staining.

Portland stone Stair threads had been painted on various occasions and there was also extensive carpet glue on the Limestone floors in the basement.

Exposed stone had been heavily polished over the years leading to a build-up of product trapping moisture in the stones.

Some sections of the floor had been filled with cement where electrical and plumbing works had been installed.

Following extensive trials and samples the OPW Conservation Architects were happy to proceed with works.

All works were carried out in small sections for better management and to limit the amount of water used. Minimal use of water is best practice when working with stone.

Carpet glue was gently scraped off using fine blades. We then proceeded to remove all contamination from the stones using pre-approved specialist stone cleaning products. This process had to be repeated several times until we brought the stones back to their original colour. The clients were thrilled with how well the stone came up once stripped of all contaminants. Now fully exposed we could assess the extent of repairs required and set out a repair strategy.

The lengthy repair strategy begins

A lengthy process of various sample repairs was carried out using different mortar mixes and replacement stones.  Once approved we proceeded with the restoration and repair element of the project.

Cement infills were very gently removed by hand to avoid damaging the adjacent stones. Repair works were a very slow and gentle process given the historic value of the floors. Most works were carried out on hands and knees.

The next task was to gently remove all mortar joints to an agreed depth. Special care had to be taken where cement was present in the mortar joints to avoid cracking or breaking the stones. Stones for replacement or repair were carefully lifted, photographed, numbered and stored away.

Replacement stone was sourced from Portland Bowers base bed quarry. Various samples were initially imported to find the closest possible match. Exact measurements were taken on site and each replacement stone was cut at source.  Replacement stones were spread out over the floor to ensure they blended in with the existing. This required some good stones to be lifted and re-bedded elsewhere to avoid a cluster of new stone in one section.

Repairing chips, cracks and dips

Stone indents from excess stones were used to repair chipped corners. Gouges and dips were repaired using Portland repair mortar. Cracked stones were glued and filled with matching repair mortar made with shavings and dust from existing stones.

Once all repairs were complete all joints were cleaned out and repointed in a grey sand and lime mortar.

Really beginning to take shape now the floors were given a final clean down and left for several weeks to completely dry out. We then returned to seal all the floors with a breathable penetrating sealer. This sealer will not alter the appearance of the stone but penetrates into the stone increasing its resistance to staining.

The restoration of these historic stone floors was a true honour and labour of love for our very skilled stone floor restoration Crew. It was a slow and labour intensive project, as previously mentioned, many hours spent down on hands and knees. Each step of the process had to be photographed, catalogued and approved by the OPW Conservation Architect before we could proceed with the next phase. Alas, even though each step of the process was meticulously photographed we were unable to take any for our own archives due to the sensitive nature of the building.

We are extremely proud of the amazing works and finish achieved here by our crew. As a Company, we are proud to have played our part in this mammoth conservation project. We hope that future generations of Members of Parliament and the many thousands of visitors who pass through Leinster House each year will enjoy admiring this beautifully restored 18th century building. These stone floors will bear witness, no doubt, to another 300 years of important historic events.

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