1. Joe used 75mm (3") foam sheet. Yours looks thinner?
I used only 50mm foam. Joe felt he needed
at least 75mm to support the concrete render surface.
I skinned mine with thinner, lighter material. It
was a gamble but 50mm was fine for my situation.
Also, I had originally planned the foam as a mould
for fibreglass. 75mm seemed overkill for a mould.
It also was about 50% cheaper going for 50mm foam.
2. Where did you source the foam?
The foam is used as cheap insulation for buildings
and coldrooms.
Any building supplies wholesaler should have a contact
for 'polystyrene foam sheeting'.
3. How long did it take?
All up, from the first cutting of tiles to first
light, about 12 months, but a lot of that was my fussy
time consuming woodwork.
4. What size work area was needed?
A shed of about 20' x 18' was fine.
5. What sort of glue was used to join the triangles?
'No More Nails Fast Grip'. It comes in caulking
gun cartridges and has a fast ' contact' effect.
This is far cheaper and goes further than 3M #77
spray on glue, a purpose made product.
6. How did you seal the seams or gaps between the triangles?
Every join had 'drywall joining tape' laid over
it and then NoMoreNails screeded over it.
This made a very smooth filled joint. I did this
both from the inside and outside.
7. Looks like you used newspaper pasted on and then painted over?
UPDATE: Concrete rendered the
entire dome as of January 2005....
This was all a cheap experiment. It is about 20
layers of papier mache! :)
Strips of newspaper were soaked in a warm water/wood
glue mix
and layered slightly overlapping each other.
If it failed I would not be too disappointed. But
it was amazing how strong it turned out.
Newspaper has a 'grain' and so it tears easily along
one direction only. So each alternate layer of
newspaper would be 90 deg different.
ie: | then __ then | then __
The very first layer was glued with wallpaper glue.
PVA Aquadhere didn't seem to glue well straight to foam.
In between every 2 or 3 layers of newspaper I'd
make a layer of random, very long strips of 'drywall' or
'gyprock' jointing tape.
By about layer 5 or so, I knew it might work, or
at the very least, be a good release layer for fibreglass.
By layer 6-7 I knew I was on to something.
I must say that, I don't endorse using this approach
in all climates of the world. Where I live we have fairly
low humidity weather year-round, and this helped
completely dry out each paper layer once it went on.
Also, I'm not sure of how my dome would go in a
cold or sub-zero climate. It may crack. Snow might be
a problem.
Note: In retrospect I would not recommend the papier mache idea anymore...too much maintenance
needed to keep it sealed and dry....any water will get in and spread like a cancer under the skin.
8. The slot looks different to Joe's. It looks like you enlarged
it?
Same as Joe's, 24 inches or so. The 'widening' you
describe was actually
my successful attempt to put an exact parallel circular
slot track in a very roughly cut
un-parallel foam slot.
9. Your sliding door looks as if it runs 'inside' the slot -How
have you done the door?
Do you have some kind of 'track' on the back
of the dome for the door to run on to?
It does run inside. But it has an overhanging weather
lip. Wheels run on the top curve of the slot.
I have about a 5/8 door and a 3/8 door if you know
what I mean.
The bottom 5/8 door removes and is the entry point
into the dome with a small ladder.
The 3/8 door is trapped in the slot and moves on
wheels the entire length to suit the sky being used.
10. Why the change of colour?
Colour is a contentious issue. The whole dome was
painted in (at last count) about 5 layers of acrylic
water based outdoor paint. First it was white.....then
green because it was too bright in my yard!
The green was hot to touch on the first 25 C day
I had, and at that stage I was worried about it all
cracking due to the heat. So it went white again!.
About 2 weeks later the brightness was too much so I
made a decision. Green it would stay. Anyway more
layers wouldn't hurt :). It's now green.
It has survived winter rains and small hail.....no
leaks....and as of January 2001, the hottest January
since 1930......nearly every day above 30 C with
many days over 40 C.
11. What wall construction did you use?
The wall is 15 steel supports on a radius matching
the dome base ring centreline, set in concrete.
It is clad in std roof / fence steel sheeting.
A bead of waterproof filler around the base concrete
and sheeting stops rising damp along with a
waterproof membrane painted inside over the concrete.
Inside slab is a centre circle, isolated from the
outer concentric slab by a gap filled with foam strip.
12. Is there anything you would do differently in retrospect?
It is a buzz making and using your own dome. First
light is a pretty cool experience.
I was inspired by Joe's success and have him totally
to thank.
Pride might make me hesitant to mention any downfalls
in my work but in the spirit of Joe's page and all
ATM pages, I must point out any negatives in my
dome so that others can at least make a change or improve.
Things I'd do different:
1: Make the door arrangement 1/3 and 2/3....There
is a tiny part of sky I
can't get for about half hour because of the overlap.
To solve it I may slice my present 3/8 door in half
and have two trapped, moveable doors in the slot.
2. When pouring the centre slab I put a conduit in
the pour from it to the
outside wall, so I could keep all cables off the
floor to stop tripping. I should have put more conduits in!!! :)
(thanks to Dominic, Paul, Clement and Tom for FAQ ideas, any others are very welcome)