In 1869 Turnbull designed a large building of four storeys plus a basement and an attic for H H Bancroft & Co, a printing company.

Every precaution has been made to procure the best material and erect the structure in a manner which will render it as thoroughly earthquake-proof as possible.

He worked for a year for the government's Colonial Architect William Clayton before setting up his own practice.

[5] Turnbull maintained his interest in earthquake-proofing buildings after his arrival in New Zealand.

In 1888 he presented a paper at the Philosophical Society in Wellington, asserting that masonry buildings properly constructed with good bricks and mortar, reinforced with iron built into the walls and joists fitted with wrought-iron anchors, would survive a large earthquake.