Sawdust Bricks? - whoever heard the like!

 Clive Johnston (Kevin's father), a semi-retired blocklayer, helped us build The Mudcastle. He not only taught me how to block lay while Kevin handled the brick production side but Clive was able to expand his own repertoire by working with adobe blocks for the first time.

Clive laying the very first adobe  brick of The Mudcastle in the  last week of January 1993.

 His overall impression of this new building material was favourable as clay didn't go 'off' like cement did giving more time to work it, less wastage etc. and it was simple to mix, mould, drill and lay. But it bothered Clive that there was some shrinkage in the moulds, that it wasn't a weather resistant product, that the mpa was low at 2 - 2.5 and the blocks were heavy. So Clive started to experiment, first with the conventional products he was used to - cement, plasticisers, hardeners etc. then moving onto more natural materials such as clay, bark and sawdust.

This brought the weight down and the mpa up but then Clive had one of those 'moments' (the 4 am kind) and the way forward was revealed in the form of a juice that remains a closely guarded secret.

Now the average mpa of blocks was 12 - 14, they weren't brittle and were 50% lighter in weight. Yay from me!

Even more amazing, the moulds could be removed from the mix almost immediately and, although still only sun dried, the blocks could be stacked or used in 2 - 3 days! Yay also from Kevin!

The blocks could be cut with any blade, even a handsaw, sanded, nailed, screwed and even glued together. And, once hardened, were weather resistant. They could be painted or sealed in the same way concrete products could and even be used partially buried as garden edgings without ill effect. 

Even better, the rigorous testing showed that the thermal rating was within the parameters necessary for compliance with the new Building Act and the product was endorsed by local structural engineer Gavin Robertson. This paved the way for Tasman District Council to pass consent for the first construction in the world of this product and the second major phase of building at The Mudcastle - two two storey turrets and a 40 metre two storey crenellated wall. None of these structures would have looked remotely authentic with the overhang verandahs required by adobe blocks to remain shielded from wet weather. This brickmaking and building phase took a relentless 16 months to complete for up to 10 men (and a concrete mixing truck that could only go backwards) and upped our overall brick tally to 20,000.

The first sawdust brick building in the world. And that's Clive on the battlements in the distance.

 Apart from the ecological benefits to the timber industry of recycling a significant waste product, the other potential applications for this as yet unnamed building product are impressive -

• Used in conjunction with fire clay, the mix becomes fireproof allowing it to be utilised as insulation for logburners
• Plastering walls and laying paths can be accomplished by virtual novices given the amount of 'play time' plasterers have with the mix
• Its strength and lightness makes it a no brainer as an alternative breeze block to the ugly concrete version we all know - imagine the saving to ACC alone if heavy lifting was able to be reduced for the construction industry!
• Its ability to be free formed and its fast moulding properties makes it ideal for making garden furniture, flowerpots, urns, pavers, tabletops and garden edging 
• Due to a key component being sawdust, the mix is perfect for use in areas where sound absorption is required
• With above average heat retention properties, spa surrounds and BBQs are possible

and Clive is just getting started!

We are looking for someone to take this product forward so that its obvious commercial potential can be explored.

Please either contact Clive on (03) 541 8200 or email kevin@themudcastle.co.nz if you would like to discuss this extraordinary discovery further.