Sawn timber post and beam frame

The old warehouse section of the Centre for the Arts building is a multi-storey timber post and beam structure, characteristic of harbour side wool stores and warehouses built all over Australia in the first 150 years of European colonisation.

Built as part of the Henry Jones IXL jam factory, the warehouse’s design exploited the economy and strength of unseasoned hardwood columns and beams to provide cheap but robust storage space. Construction was simple. Large section timbers were used throughout, rough sawn or finished with a broad axe or adze. Where the member’s joined, they are housed into each other or worked into mortice and tenon joints and strapped with steel.

Tins of jam were often stacked to the ceiling. The original frame had a capacity to support live loads of 700 kg/ m2 but this proved inadequate for the loads applied. Intermediate columns were installed on the upper floors and were supported by an additional set of knee braces on the ground floor columns. Excessive loading and the uneven seasoning of the timber has led to several corbels crushing. Many of the columns are out of plumb, due again to the excessive loading, movement in the timber and settlement in the pile footing. Below the first floor the columns lean to the west while between the first and second floors they lean to the east. This is in part due to the absence of any effective bracing systems. Though the knee braces may have been intended to provide horizontal bracing, they are probably ineffective due to the high shrinkage of all the unseasoned hardwood elements.

In an effort to contain the movement of the floors, raking shores were installed in about 1940 and again in about 1955. Notwithstanding the excess loading and the slope in the columns, the frame is structurally sound and the warehouse has been refurbished to exploit both the colour and texture of the heavy timber elements. It currently houses part of the University of Tasmania.

Owner

The Tasmanian Government

Location

Hunter Street, Hobart

Date Completed

c. 1920

Description

The four storey warehouse has a heavy timber post and beam structure, enclosed by masonry facades. The internal frame has lines of large section timber columns supporting bearers, hardwood joists and two layers of timber flooring.

Constructed from unseasoned hardwood, each column assembly consists of a sawn column, a corbel, a pair of knee braces and two floor bearers, all tied together with flat steel. The knee braces are roughly housed into both the column and the corbel and are fixed with a through bolt. The corbel supports the two bearers and supplies the seat for the next column. On the lower floor, the columns have an additional pair of braces below the knee braces. These support additional columns on the upper levels that prop the bearers mid span.

The frame was braced with solid hardwood diagonals about 20 years after construction to restrict a developing lean on the first and second floors. The building has a sawtooth south light roof of triangular oregon trusses. These have mortice and tenon joints, held together with tie rods and flat steel brackets.

References

University of Tasmania, 1981, The Centre for the Arts, Hobart -Technical Papers, Hobart.

Legend

1. Column, 390 x 370 mm

2. Column, 360 x 360 mm

3. Column, 285 x 285 mm

4. Column, 250 x 200 mm

5. Knee brace, 200 x 200 mm

6. Corbel, 410 x 260 mm

7. Corbel, 360 x 250 mm

8. Floor bearers, 2/400 x 145 mm

9. Floor joists, 365 x 75 mm

10. Oregon roof truss

11. Steel connection bracket

Captions

a. Masonry facade

b. Line of columns

c. Raking shore