The buildings were generally constructed by the family and other workers, without the aid of architects, planners or even expert carpenters. The earliest mill buildings were built in the 1930's and building construction continued until the mill closed in the 1960's.

The working mill buildings were mainly constructed from unfinished red cedar and Douglas fir. The wood was logged nearby and cut at the sawmill. The building materials are described as dressed logs, sawn timbers, dimension lumber, corrugated iron and metal pins, plates and rods.(Heritage Conservation Program, Mclean Mill National Historic Site Port Alberni, British Columbia. Condition and Impact Assessment: Main Mill Building. Ch.6, 1) The sawmill is located in a Coastal Western Hemlock zone and the surrounding forest consists mostly of western hemlock, Douglas fir, grand fir and western red cedar. (Chathan,Robert Mclean Mill Historic Site, 1997 Archaeological Investigations and Impact Assessment. p.3)

The buildings were designed to be purely functional and utilitarian, and the use of local timber gives them an appearance of being part of their environment. In the wet western Vancouver Island rainforest climate it doesn't take long, usually about 25 years, for the wilderness to reclaim buildings. Most of them were beginning to rot from damp. Any equipment which was left exposed, such as the green chain, was practically rusted away.

Building materials at the R.B. Mclean sawmill site evolved with the technology of the mill itself. In the beginning rough plank boards, the best the mill was capable of cutting, were used in the construction of the buildings. As time went on and the milling techniques and technology got better, then more refined timber was used. There is a significant difference between the materials in the early and later buildings.