Prefabricated off site, it took Lachie and a team of three little more than two hours to erect the sugar gum frame on site in the clearing at the Imal biorich plantation.

While careful preliminary craftwork is essential to the traditional mortise and tenon building technique, prefabrication is becoming increasingly fashionable today. It allows for quality control and pre-packaging has enabled a faster roll-out of new houses to replace those lost in the Black Summer bushfires.    

​The bottom plate beams for the 21C drop slab hut were laid out on a grid of ‘granite’ staddle stones. Bolts through the beams were nested into a central hole on top of each stone. Armed with a spirit level, Lachie adjusted the height of each bolt, until the base floated perfectly flat above the ground’s surface.

The stones serve two obvious purposes and one not-so-obvious: they ensure underfloor air flow, stop termites and offer the clearance for lifting the hut and transporting it to another location. 

Like a jigsaw, the post and beam pieces slotted together. Unlike a jigsaw, Lachie had numbered each piece, so the team knew exactly where each piece was supposed to go. 

Corner posts were wrestled into place. Uprights for window and doors carried to their assigned slots. Then came the moment to bring out the modern machinery to do the heavy lifting of the top plates. Lachie had hired a Telehandler with a wide forklift for the day. Up and over went the long beams, with the team atop ladders gently guiding these nine metre-long heavyweights onto the post-top tenons.

As each of the four sides was capped with a beam, pegs were hammered through the corner posts and beams, anchoring the 3D jigsaw into a fixed pattern. Finally, the Telehandler raised its articulated arms high and added the gabled framework for the roof. The oiled skeleton of the drop slab hut gleamed firm and proud, the solid wooden frame at one with its natural surrounds.
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​The high levels of tannin in black wattle makes the wood rich red in colour. A beautiful stable timber, it grows well in low rainfall, and was once widespread, thriving in the heavy clays of the basalt plain that extends from the outskirts of Melbourne to beyond the South Australian border. As a common local timber, we thought it was an ideal candidate for the flooring and window frames in the 21C drop slab hut.
 
From settlement’s outset, however, black wattle (Acacia mearnsii) was consigned to a low value destiny – similar to sugar gum. With its bark found to contain 40 per cent water-soluble tannin, industry seized on it as ideal for cleaning and preserving animal skins. Countless numbers of black wattle were flayed alive, with their bark stripped and bundled up for making leather or scouring sheepskins in the cities’ tanneries.
 
Sent overseas for its tannin qualities, black wattle soon developed a poor reputation. From South Africa to Germany, it became regarded as an invasive weed. Its tough black seeds readily germinate once damaged. After fire, it suckers prolifically creating dense thickets that eliminate other species. Around 15yo, the species becomes untidy, literally falling apart.
 
Tainted by its past, the best that agroforestry manuals can recommend for black wattle is to plant it as a nurse crop for more valuable timber species. When grown in alternate rows, the fast growing black wattle forces the more favoured species of eucalypt or exotic timber to grow straight as they strive to reach the sun. After 5-10 years, the manuals recommend cutting out the black wattle for firewood.
 
At his property near Mt Egerton, Ballarat Region Treegrower (BRT) farm forester, Campbell Mercer, put this formula into practice. In 2003, he planted a 20 acre woodlot of black wattle nursing a range of species from brown stringybark to cypress.
 
Fifteen years on, the black wattle was outcompeting everything else on a wet, south-facing slope. Encouraged by BRT’s resident pruning fanatic, Phil Kinghorn, Campbell had over the years pruned some of the black wattle and he thought: “There must be a better use than firewood, particularly as some of the trunks are in excess of 20cm and clear to 10’.”
 
Using Phil Kinghorn’s mobile Lucas Mill, they produced some 1” and 2” boards with ease. There was no shrinkage or end checking and the milled boards had a distinctive wavy grain pattern and swirls of dark red. They sent the boards to specialist timber retailer, Fairwood, in Melbourne for appraisal. 

Fairwood knew nothing about black wattle and were amazed at the colour and how it sustained such a good polish,” remarks Campbell. “Given it grows so strongly and has the added benefit of offering a dense and clean burn for any firewood thinnings, I don’t understand why it’s not a popular timber plantation species.

“Maybe it’s something to do with the tree being naturally very branchy, making it totally unsuitable for timber unless pruned.”

Campbell and Phil went on to mill six cubic metres of 1”and 2” boards of black wattle. We are the first to buy the boards, with Lachie picking up 92 lineal metres on a fine day this spring. When he finishes them for flooring and frames, who knows what standard they might reach? We’ll keep you posted!
 

Hopes were always high for a very productive spring bird survey at the ImLal Biorich site following the wet winter and pleasant survey conditions on the day, and the small group of birdos were not disappointed – a huge tally of 46 species was recorded along our usual 90-minute circuit! This is an impressive number of species for a single survey – for context, our previous visits in spring and winter 2019, yielded 28 and 22 species respectively.

Firsts for the spring bird survey included a Sacred Kingfisher and a Musk Duck on the dam. We watched a pair of swamp harriers  hunting without him among the Lal Lal Wind Farm turbines. For a full report of the spring bird survey by leader Grant Palmer, visit the menu for the Bird Survey.

Traditionally, in Europe and North America the pegs for the holed post (mortise) and grooved beam (tenon) are made of oak. That’s the way it’s always been.
 
In what is possibly a world first, Lachie decides to try shaving down some sugar gum offcuts. We are determined to use as many local materials as possible. What innovation ever occurred without taking a risk? Lloyds of London refused to insure the first Tasmanian clippers made of the only timber available to the local boat builders in the early 1800s – blue gum. One hundred years later they were still plying the Derwent.
 
As a Class 1 naturally durable hardwood, we know that sugar gum will have more than sufficient strength to hold the hut’s frame together. The known unknown is whether or not the dense sugar gum will shave to a taper smoothly? 
 
Lachie starts roughing out the offcut’s taper with a small axe. The sugar gum offcut is clamped down to the neck of his home-made saw horse. He mounts and begins work stropping back and forth with his two handled shaving knife, whittling the pegs down to a point. “It's smooth as…,” Lachie declares.
 
Lachie estimates that he will be able to produce the 50 or so pegs for holding the hut’s frame together in little more than a day astride what he fondly dubs his “pleasure pony.”
 
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For a small build, chainsaw milling is another means of keeping costs down and avoiding the middle man. 
 
Lachie uses a Stihl Magnum M5 661C chainsaw as the cutting agent, with the log lain out on a Logosol M8 Sawmill. A 45yo gantry hoist designed by a friend of his grandfather provides the lifting heft to swing the sugar gum logs on and off the saw bench. These three items are capable of handling logs up to five metres in length and 60cm in diameter – more than enough to build a house.
 
“It’s empowering once you master the skills,” says Lachie. “You can cut anything you need for a hut or house on your own.”
 
Like any craft, the truly limiting factors are the hours and hours of dedication required to acquire the cutting skills and the physical strength to turn logs around and heave them onto trolleys. The old, slow ways are not for the desk bound.
 
It’s just six weeks since the trees were felled and the wood is still moist and responsive. Lachie guesstimates that green wood is four times easier to cut, drill and chisel than inert and inflexible kiln-dried timber. The downside is that it shrinks and splits more easily. Not a viable option for the ‘perfect’ finish, but fine for the rugged splendour of the 21C drop slab hut.
 
Lachie is assembling all the hut’s components off site. He’s crafting a jigsaw in his back yard and won’t put all the pieces together until they are freighted to the clearing in the ImLal biorich plantation.
 
Back in his yard, Lachie sets the sawn 175mm square posts and 150mm beams straddling a series of saw horses. He begins preparing them in keeping with the ancient mortise (old French for hole) and tenon (tongue) pattern. Chiselled and shaped beam ends will slot into grooves on post tops. Holes are drilled through each post’s tenon and corresponding mortise. 
 
When assembled on site, a wooden peg will be hammered through each hole, wedding beams and posts together into a sturdy frame. Like people standing in a line, their outstretched arms on top of each other’s shoulders.

Granite foundation stones are a perfect match for the 21C drop slab hut. When quarried locally the old way, they are low in embodied energy. So, although high in weight and density, the granite’s carbon footprint is light. An altogether appropriate product for the 21st century upgrade of our drop slab hut.
 
Known as ‘staddle’ stones, the granite foundation stones will raise the drop slab hut clear of the ground, enable air circulation and termite resistance, while offering the clearance that allows the hut to be moved around the ImLal plantation. Flecked grey-white, the staddle stones will have a solidity and natural beauty. 
 
Lachie sourced the granite from a small quarry on the flank of Mt Alexander owned by father and son team, Vin and Brent Oliver. Harcourt granite, as it’s named from the local area, formed the base of many of Melbourne’s grandest buildings in the 19th century. Famously, the structural slabs on which the Sydney Harbour Bridge sits are Harcourt granite.
 
Structural bases are these days made of concrete, the most widely used building material in the world., estimated at an average of two tonnes for every man, woman and child on Earth. A processed product, concrete not only consumes energy, but as Vin, a third generation stonemason, remarks, it’s not made for the ages like the polished tombstones he creates, rather “concrete crumbles.”
 
Most granite these days is blown to smithereens for road construction or as a filler, Vin said. In the old days, five tonnes was the limit a horse-drawn wagon could carry. Now, the smallest slabs of granite start around nine tonnes.
 
Vin demonstrated the traditional way of cutting a slab of rock. He drilled a line of holes, seeded each with two metal ‘feathers,’ hammered in wedges between the feathers, then prised the rock apart with a crow bar along the fault line that sprang up between the wedge-holes. Physical labour is the major energy input when deploying the slow, old way to split stone. Not only does it respect the rock, but the end product is a natural thing of beauty.
 
And, unlike a concrete base, the staddle stones will rise out of the earth, not smother it.

Only seven of the original plot of 52 sequoias has survived the onslaught of the bouncing roos on the ImLal North site. They don't seem to like the swampy conditions much either. The sequoia pictured is as old as the young Nate on the left – 10yo and way behind Nate in the growth stakes.

Phil on the right shows his patented ring of steel  guard for keeping the roos at bay – for now.