When there's a historic building involved, Mason Architects is usually called in to help renovate or restore it.

The Honolulu architectural firm has occupied a niche for preservation research, historic restoration and adaptive reuse of historical buildings for the last 25 years. The midsize firm recorded an estimated $5.4 million in billings last year.

Principal Glenn Mason started Mason Architects 11 years ago and was a partner of Spencer Mason Architects 14 years prior to that.

The firm is now helping Kalahikiola Congregational Church through the final stages of restoration from the destruction it suffered during the October 2006 earthquake.

Luckily, the 1855 church's roof structure (made of rare hand-hewn ohia) and tower were in good shape, said Mason, and were able to be kept in place. Most of the church's windows were also salvageable, except for two, which have since been reproduced. The church's original doors were also saved.

Mason's approach is to preserve whatever is original as much as possible, and to replace what can't be kept with the closest match.

The 154-year-old church's stone walls, which crumbled during the quake, are being recomposed with cinder blocks that will be plastered by specialists to look like the original one mimicking sandstone blocks.

“;The appearance will be historically accurate, inside and out,”; said reconstruction committee co-chairman Patrick Ku.

Multigenerational members of the church in North Kohala were devastated and heartbroken over the destruction but are now seeing the light at the end of the tunnel as the walls come back up, said Ku. Work to rebuild the church began last December.

The small congregation of about 60 active members has been meeting in the parish hall since the disaster hit.

Ku says the church's $1.1 million restoration is on track for completion in October, about three years after the earthquake. Kikiaola Construction Co. is doing a lot of the work.

“;The reason we picked Glenn is he tries to maintain the historical accuracy of the church, and that's very important to us,”; said Ku. “;Everything will be brought back as best it can to what it was prior to the earthquake.”;

Many of the projects require a good dose of patience, given that they are slow-paced.

Typically, historic projects need to go through numerous permitting hoops and sometimes consultation with the state and national registry of historic places.

Past Mason Architects projects range from 13 phases of restoration work at Iolani Palace to the renovation of Hawaiian Hall at Bishop Museum, and the restoration of the 1905-era Stack Building in Chinatown, which has now been transformed into a retail space.

The firm also has researched the history of Kakaako for the Kamehameha Schools' master plan, replaced the windows at Kawaiaha'o Church and even built a custom, open-air home for Rusti the orangutan at the Honolulu Zoo.

The 8,168-square-foot, two-bedroom home for Rusti (and now Violet), complete with swinging ropes, hammocks and vantage viewpoints, was a unique, one-time project for the architecture firm.

Mason and his staff of 24, which includes nine architects and five architectural historians, also work on residential homes, park service projects, consulting work and some federal work, including design-build projects for the military.

Because Mason Architects occupies a specific niche and does a lot of government work, it hasn't much felt the impact of the slowing economy, according to Mason.

Other projects in progress include plans for interior work on the 1874 Kohala Girls School on the Big Island, repairs for the Hilo Federal Building and restoration of Club Hubba Hubba in Honolulu's Chinatown, which is under design, with drawings due out in about two months.