Diederik and Tara Haneveld’s account of building a fire bunker on their property Bodhidharma, at Shepherd’s Flat near Daylesford, Vic – passed on to us by Soumitri Varadarajan – is worth reading. Yes, there were fires in the Wombat State Forest near Daylesford.
“The myths surrounding container fire bunkers eg they will become an oven etc can be summed up in one word, horse…..
Once they are in the ground they are cool as a cucumber. It is true that soil is the best insulator.
So a few things I have learnt doing this project. First and foremost buy a good, I mean a GOOD container, if it already has a lot of dents and rust it will make your job twice as hard. Too many dents make it prone to crush easier and a lot of rust means more work for you sanding it off after it has been delivered (make sure you unload it close to the hole) you can begin your reinforcing.
We used 100mm x 50mm square steel and it was 5mm thick. I am glad we did as the container crushed a fraction and we had to weld more reinforcing on the inside. For the roof we put a length of 100mmx50mm down the middle and a “c” purlin on top of it, then one either side at a gap of 450mm to take the corrugated iron roof. I am also glad we did this as the roof would have sagged quite considerably with the soil on top of it.
Next comes the bitumizing which must be done on a hot day otherwise it does not flow. It took one person 6 hours to do this. We did the roof as well.
Next was solving the problem of being able to close the door from the inside. This turned out to be simple, we took the closing bars, which seal the door shut, and ground off the closing mechanisms on the outside, so they could not operate. We then welded two angles, one on each door, on the inside, and dropped a large piece of timber across it like an old castle door I guess. This insures you can’t get locked in. It hasn’t sealed 100% but I am confident with a little bit of fiddling, it will.
Marking out the hole was simple but don’t expect to get it with an even 200mm fill gap around for your rock-fill. With a massive excavator digging it out, it just doesn’t work that way. Allow extra rock. We made sure the bottom of the hole was sloping down to allow for water runoff.
We leveled the bottom of the hole with 50mm blue metal and lowered the container in. That was one of the easiest tasks. We put industrial plastic over the roof and started the backfilling. It truly was a shock that the walls bowed, even if it was only marginal.
We are confident with the new centre support in place nothing more will move. You will notice in the photos the supports for the retainer walls on the top and sides, this stops the soil from slipping until the front airlock is built. I will take my time doing the airlock as I don’t like block laying much. So, the cost so far.
3) blocks…..1,000 with cement
5) excavator and blue metal…3,000
6)odds & sods…200.00
The welder was a friend and worked for barter, the rest my wife and I did and will do. Labour has not been factored in.”
Thanks for this Diederik and Soumitri.