Petra Heights: Stone towers rise on Finchley Road

A new residential development named Petra Heights has emerged on Finchley Road, characterised by its distinctive towers constructed from large, rough-hewn rock slabs. The project, designed by architect Amin Taha, aims to bring structural stone back into mainstream use, a practice largely abandoned for over a century in favour of cladding.

Eco-friendly Construction with Stone

Read Next in Barnet Press2 min read

Finchley play centre Gymboree to close after 27 years

Landlords have ended the lease for the pre-school music and play centre located at the O2 Centre.

The towers are built using three-metre slabs of materials including pink basalt and igneous larvikite. Taha claims this method of construction is not only more economical but also reduces carbon emissions by approximately 30% when compared to buildings made with concrete or steel. He further noted that if a proposed internal frame of cross-laminated timber had been used instead of concrete, the savings could have reached 75%.

This approach represents a significant effort by Taha and engineer Steve Webb to revive the use of structural stone. Their previous project, Clerkenwell Close, also built with substantial stone blocks, was shortlisted for the Stirling Prize in 2021. Webb, whose firm Webb Yates developed a stone pylon prototype, advocates for stone's stiffness and stability to reduce steel requirements, envisioning a new era for stone in construction.

Development Challenges and Design

Related Borough Coverage3 min read

Hertsmere plans spark Green Belt and transport fears

New housing developments near Barnet's border raise concerns over infrastructure and congestion.

The design for Petra Heights was initially conceived in 2015. The project encountered numerous obstacles throughout its development, including shifts in site ownership and supply chain disruptions attributed to the pandemic. These challenges led to modifications, such as the substitution of the original mass timber frame with concrete, which Taha suggests proved more costly. Consequently, stone elements were made larger to support the increased weight, with some sections reinforced by steel diagonals.

Supply issues during Covid-19 meant that while the lower sections of Sicilian basalt were already in place, the remaining floors were completed using igneous grey larvikite from Norway. Both types of stone were treated with a reddish wash to ensure a consistent appearance. The towers, ranging from six to ten storeys, are linked by a central lift and stair core, with upper levels connected by a bridge. The stairwell is exposed to the elements and leads to a communal roof garden, contributing to the building's rugged, mountain-like aesthetic.

Reviving Stone's Role in Architecture

Taha has expressed that developers often perceive structural stone as too unconventional for the British public, who he believes prefer traditional brick. He points to popular towns like Bath and Edinburgh, built predominantly of stone, as evidence of its enduring appeal. Steve Webb has been particularly critical of brick construction, describing bricks as a heavy, energy-intensive decorative element that adds significant weight and requires extensive structural support. He argues that modern construction often inverts the historical role of walls supporting floors, leading to inefficient designs.

The slabs used at Petra Heights, some three metres high and 10cm thick, were transported from Norway. The construction team managed to erect the full height of the lift shaft in a single day. The names of the architects, engineers, masons, and contractors are inscribed on the building in a runic typeface, with the intention of attributing praise or criticism directly.