people who like to have sex with goats that are on fire
And the search engine, seeking clarification on the query, responded with :
"Please specify breed of goat?"
Of course everyone knows that search engines don't ask for clarification, but
the joke would probably lose a little something if we didn't pretend they did.
Anyway, in the spirit of this sanguine belief that the net knows everything,
and in the context of trying to build my own walls, I've been attempting to get
a sensible answer to the perfectly sensible question : "Exactly how much does
a combined panel of concrete and sandstone, 20 centimetres thick, 2.4 metres high,
and 2 metres wide, weigh?"
Actually that's not all that hard to work out. I know the mass of
a cubic metre of average sandstone, and also the mass of a cubic metre
of concrete, so I can come up with a worst-case scenario for the total mass,
given that I intend to have no more than 25% of the wall made from sandstone,
but what I really need to know is how thick the slab would need to be to cope
with this kind of wall, if I wanted a rectangular slab floor about 6 x 8 metres.
Which I do.
I've heard some absolute horror stories about slabs .. but since bedrock is such
a long way down in the area of my would-be building site I can't really
avoid one. Unless I go the truly, horrendously expensive approach of capped pile
and beams, where they dig cylindrical holes down to the bedrock, fill with concrete,
and then put beams across those piles. It seems an astonishingly arduous
process .. and the idea of banging up a few broken tree limbs and covering the
thing with a dozen layers of glad-wrap is beginning to have some appeal.
At least for the summer months.
Of course I have to factor in the weight of the insulation and inner cladding, which
normally wouldn't be an issue on an average 10cm slab with conventional walls, but the combined mass of the
tilt-up external wall and the possible three or four-string 200mm strawbale insulation,
makes it look like it might become an issue. Yesterday in Sydney was the coldest December
day we've had in this city since 1924. So much for the greenhouse effect. Catering
for a few cold decades seems the sensible thing.
Assuming I'm using medium-strength concrete for the walls, that's between 3,000 and 4,000 pounds
per cubic yard, which is a stupidly useless measure, but the patently not-all-knowing net
couldn't provide anything more useful. But it's relatively easy to convert to something
understandable to an educated human[1], and equates to somewhere between 1,780 and
2,373 kilograms per cubic metre. Which sounds like a lot.
But I'm luckily not putting in metre-thick walls.
I hope to use embedded lumps of flat (at least on one side) sandstone, which won't add
anything to the structural integrity -- that's just there for the aesthetics.
Again, the net's predominantly populated by non-cognoscenti types who
insist on using deprecated units. (Bloody yanks.)
Granite's about 168 lbs / cubic foot = = 2,691 kgs / cubic metre
Limestone's about 162 lbs / cubic foot = = 2,595 kgs / cubic metre
Marble's about 168 lbs / cubic foot = = 2,691 kgs / cubic metre
Sandstone's about 143 lbs / cubic foot = = 2,291 kgs / cubic metre
Slate's about 175 lbs / cubic foot = = 2,803 kgs / cubic metre
I'll probably end up using a combination of granite and sandstone, depending how
much local sandstone I can quarry from the property, so let's assume an average
stone weight of 2,400 kg / metre3. The subsequent assumption
is that there'll be about 20% of the mass occupied with stone, the rest rebar and
concrete, which brings us to, say, 2,200 kilograms per cubic metre. At least,
that's a fairly safe number to work with, allowing for over-engineering and so on.
Total wall mass will therefore be :
thickness x height x width x 2200
So with 6 x 8 metre dimensions, and walls that are 2.1 metres high and 150mm thick :
0.15 x 2.1 x ((6 x 2) + (8 x 2)) x 2200 = 19,404 kgs
Which simply can't be right. That's a fucketload of concrete. An impossibly
heavy structure. But maybe it is right. It's only 20 normal cars worth, and the
total area is enough to fit 8 cars. Or the same as 12 tractors worth, and the
existing shed got a 4" floor to cope with the tractor (otherwise it'd have got
a 3" floor).
And realistically, with the panels going up in 2 metre wide lumps, and every third one having
a window (and two of them having doors), that takes the weight down quite a bit. Assume a window
is 1m x 1m, and really is on every third frame. There's roughly 14 panels, so 5 windows,
so (5 x 1 x 1 x 0.15 x 2200) = 1,650 kgs less. Probably a goodly amount more, perhaps double
that figure, since windows are both easier to make, and more fun to look through, than stone walls.
But while that takes the external wall weight down to around 17 tonnes, that figure still doesn't include
internal cladding, insulation, roofing & ceiling cladding, rebar in the walls, or even furniture (I imagine
king size waterbeds aren't light beasties).
What I need is someone who can take these numbers, factor in their accumulated wisdom from
doing this stuff for the past twenty years, and tell me how thick the slab needs to be.
But where to find such a person?
To reduce costs I think I'm going to have to do my own form-work, as well as all the finishing &
screening work.
Which sounds like fun.
I've never done anything like that before .. but how hard can it be?
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Vaguely related to building homes .. I found out a couple of weeks ago that they (the proverbial
they) are going to pull our house down in two or three years. The house was purchased
with an affectation applied to it from the local main-roads department, but that notice had
been on houses in this area for about 30 years, and no one ever expected them to actually ever
do anything like build a road around here.
The way the road goes is at right-angles to the vast bulk of traffic flow, and it won't
actually assist the trouble spots in the area. The road won't connect the two main
roads in the area, and no one's quite sure exactly what it will connect to at either
end. With a state election coming up in a few months everyone's been very quiet
about it, but if I know, then everyone knows.
Of course, financially it's an absolute boon. If we were three houses either side then we'd
have no compensation, and instead have a bloody great road 50 metres from us, with lots of
heavy traffic throughout the day and night. Pity the poor fools in that position. But
the affectation obliges the roads authority to purchase the house at market prices, which was
always something I found curious (since the property was purchased at something less than
market price because of the very same affectation that guarantees a decent buy-back
price).
And the timing is probably going to be perfect. Olive production should be starting to
be respectable in two or three years from now, on the farm. Boredom of living in the
burbs will be reaching critical levels. Inverting the default home locations & default
work locations will be a moment of much joy.
It'll be the second house I've lived in that's been pulled down, which is kind of spooky because
I've only spent significant periods of my life in three abodes.
The first one was where I'd lived for twenty years. This one for 5 or 6. Lots of
good memories, plus the inevitable handful of bad ones of course. The problem I've
been pondering these past few days is what to do with the in-ground plants - the kiwi vines
are producing fruit this year, the tangello is positively laden with fruit. I refuse
to have them bulldozed ignominiously .. so there promises to be much Fun on that front too.
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