In building a hut from green wood, drop slab walling – according to Lachie – delivers the most satisfying blend of benefits over other materials, such as weatherboards, vertical slabs or corrugated iron.
The drop slabs for the walls of miners’ and cattlemen’s huts were traditionally riven lengthways from a messmate or mountain ash log using a broad splitting axe or wedges. Lachie’s 21st century refinement is to replace pure brawn and deploy what is known as the Alaskan chainsaw mill technique.
Lachie began by felling a messmate in private native forest on top of the Dividing Range in central Victoria. Messmate (Eucalyptus obliqua) is the dominant species in the dense forests of the south-western Divide. It splits easily and was described by 1850s gold miner William Howitt as “the most useful of trees” for mine props and hut construction. A sturdy hardwood, messmate holds the honour of being the first tree to be encountered by a European explorer; namely, Dutchman Abel Tasman as he skirted the southern end of the island named after him in 1642.
Lachie’s chosen messmate was tall and straight with little taper – ideal for cutting into uniformly thick slabs. Under the Alaskan innovation, an aluminium frame is fitted above the chainsaw bar. The rigid frame guides the chainsaw, ensuring it slides evenly as it cuts longitudinally through the log. This simple setup replicates in miniature a mobile sawmill. Such downscaling meant the tree fellers could sled with huskies into back country, find a towering conifer and fall and disassemble on the spot.
To remove the first curved outside flitch, Lachie aligned a homemade rail/ladder along the centre of the log. This assures that the first longitudinal cut through the log follows the true plane between the pith or centre of the log at each end. Crude judgement of thickness by eye is abandoned. Prior to slicing off each quartersawn layer of 2” slabs, Lachie measured precisely at log ends. The consistency achieved rivalled a loaf of Tip Top.
The drop slabs for the walls of miners’ and cattlemen’s huts were traditionally riven lengthways from a messmate or mountain ash log using a broad splitting axe or wedges. Lachie’s 21st century refinement is to replace pure brawn and deploy what is known as the Alaskan chainsaw mill technique.
Lachie began by felling a messmate in private native forest on top of the Dividing Range in central Victoria. Messmate (Eucalyptus obliqua) is the dominant species in the dense forests of the south-western Divide. It splits easily and was described by 1850s gold miner William Howitt as “the most useful of trees” for mine props and hut construction. A sturdy hardwood, messmate holds the honour of being the first tree to be encountered by a European explorer; namely, Dutchman Abel Tasman as he skirted the southern end of the island named after him in 1642.
Lachie’s chosen messmate was tall and straight with little taper – ideal for cutting into uniformly thick slabs. Under the Alaskan innovation, an aluminium frame is fitted above the chainsaw bar. The rigid frame guides the chainsaw, ensuring it slides evenly as it cuts longitudinally through the log. This simple setup replicates in miniature a mobile sawmill. Such downscaling meant the tree fellers could sled with huskies into back country, find a towering conifer and fall and disassemble on the spot.
To remove the first curved outside flitch, Lachie aligned a homemade rail/ladder along the centre of the log. This assures that the first longitudinal cut through the log follows the true plane between the pith or centre of the log at each end. Crude judgement of thickness by eye is abandoned. Prior to slicing off each quartersawn layer of 2” slabs, Lachie measured precisely at log ends. The consistency achieved rivalled a loaf of Tip Top.
Back in the ImLal clearing, the long slab lengths are transformed into drop slabs when cut into short lengths and slotted into place between the standing posts of the hut’s frame. Literally, they are dropped into place from the bottom plate beam upwards; one on top of each other, with gravity replacing the job of glue or mortar in binding the wall together.
“It’s so simple and workable,” says Lachie. “The short horizontal lengths provide lateral strength without any fixing. Plus their small size makes them easier to handle and you avoid the shrinkage problems faced with vertical slabs.”
“It’s so simple and workable,” says Lachie. “The short horizontal lengths provide lateral strength without any fixing. Plus their small size makes them easier to handle and you avoid the shrinkage problems faced with vertical slabs.”
Besides cutting into lengths, the only other essential characteristic of a drop slab is to create a 30 degree bevel top and bottom. Flat in profile, slab edges sloping uphill prevent rainfall finding its way inside.
Why, you may ask, do slabs need to be so thick? Two inches is enough to prevent distortion and, just as importantly, offers excellent insulating properties – almost the equivalent of a double brick wall.
Why, you may ask, do slabs need to be so thick? Two inches is enough to prevent distortion and, just as importantly, offers excellent insulating properties – almost the equivalent of a double brick wall.
Lachie sees no need to reinvent the drop slab wall. “What I love is that you’re making a whole wall from one piece of wood. As well as cladding, you’ve got a moisture barrier, weather seal, insulation and internal lining.”
And in the hands of a craftsman, the drop slab wall is a work of art. What’s not to love?
And in the hands of a craftsman, the drop slab wall is a work of art. What’s not to love?
