SHELVING, free standing or along the walls.
No such thing as too much storage space!
Make it wide enough and strong enough to double as a 'Bunk' in the event you have to live there for an extended period.
Some 'Economy' 2"x4" Studs and some metal joist hanger brackets make a simple, but strong frame for heavy duty shelving, and a 4'x8'x3/4" piece of plywood ripped down makes for 16' of 24" wide shelving that will hold more than a grown mans weight very economically.
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WATER.
Some provision for water storage should be made in the even of blizzard, or illness to where you can't get out and bring in water.
A lot can be done with plastic barrels and some PVC/Fittings/Glue!
For me, that would probably be in a barrel(s) in the attic/rafter space since stored there empty it would out of the way, and if full, gravity would feed my water needs.
Being in the rafters should also keep it from freezing.
Small scale storage can be done with nothing more than 5 gallon buckets on the sheves or stacked on the floor, but that takes up some of your floor space that is already in short supply.
I would suggest a sink with drain that goes out to a 'Sump' filled with rocks...
Just a 'Gray Water' sump, hole filled with rocks with your drain leading into it.
Sink can be nothing more than a larger stainless steel mixing bowl with a common bathroom sink drain installed in the bottom of it.
We are talking a 'Bowl' with a 'Stopper On A Chain' here, not fulling working lavatory...
This is not a 'Solid Waste' removal system, it's for washing dishes, shaving, maybe emptying bladders in the middle of the night...
It's not a 'Slop Bucket'...
(and if you don't know what a 'Slop Bucket' is, We can go into that later)
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PRIMARY BED.
This one is easy for me since I like sail boats...
HAMMOCK! Really wide hammock if it's two people.
Folds up in a flash to store and takes up virtually no space!
Can be made from ropes, '550 Para-Cord', wire or about anything else you can call 'Cordage'.
I got hooked on Hammocks in the Marine Corps when I spent several months 'Operational' and didn't often have a bed to sleep in, but a 'Fish Net' hammock took up very little room, weighed very little, went up about anywhere from between two armored vehicles in the desert to 100 Feet up in tress in the rain forests!
Jungle Hammocks were my favorite, they had bug netting!
It was very nice having an 'Apartment' I could put up and take down in less than 5 minutes no matter where I was!
Fish nets or heavy material (Canvas/Sheeting) make good hammocks.
I spent one summer camping in a hammock made from 2" saplings on the ends, and that bright 'Safety Orange' plastic fencing! Made a GREAT hammock...
Now, don't hang a hammock like you see the movies or on those stupid things you see in peoples' yards...
SPLAY the two 'Head' ropes out, like they are both going to different trees so the hammock spreader bar doesn't rotate on a center axis!
That will make them as rock steady as you can possibly imagine!
(even my girlfriend can't flip us over, and she can fall down on flat sidewalks!)
OR,
You can lay in the hammock 'cross-ways' to what you see on TV...
Lay Parallel with the spreader bars across the hammock...
This is more for one person than for two people, since if there are two, you will have a tendency to 'Run Together' in the middle...
Cowboy Hammock,
Take a 4x4 frame, drill 3/4" holes about 6 or 8" apart all the way around, and stretch rope back and forth through all the holes, cross ways and long ways, weaving the rope as you cross other ropes.
The 'Criss Cross' weaving makes for a suspension bed that is surprisingly comfortable.
When you are not going to use it for some time, you can cut a piece of plywood to put over it and use it for a bench or shelf, and if the need arises, you are ready to go!
.........
You want to stay away from conventional 'Mattresses' for this purpose...
Mattresses don't store very well in non temprature and humidity controlled environments.
They have a tendency to collect moisture, mold, mildew, rot, collect bugs, parasites, and just generally get filthy.
They are very hard to store in 'Moisture Proof' containers because of their size, even if you seal them up in plastic & tape, that isn't going to keep the bugs and rodents out!...
You are better off with CLOSED CELL foam pads
(not the 'Sponge Foam' that is used in couch cushions and pillows)
Blankets, rugs or anything that is easy to store and you can take out and wash, beat the crap out of and generally boil if they get dirty or parasite infested.
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TABLES.
Shelving isn't the same as a 'Table' you can get your legs under, entertain guests, work on some larger project you need to be about to get around and over,
Or put an injured person on to render first aid.
Again, this can be as easy as a double thick slab of 3/4" plywood on barn hinges screwed to the wall,
(so it will fold up and out of the way when not in use)
And a couple of barn door hinges on legs so the fold down when you let the table down...
Or as complicated as one of the folding tables with plastic tops from Wally-World or somewhere else.
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HEAT.
Does anyone know what a 'Rocket Mass Heater' looks like or how it works?
rocket mass heaters-super efficient wood stoves - Google Search
http://www.oasisdesign.net/energy/woodheat/index.htm
In the case of outdoor cooking, a rocket STOVE...
http://solarcooking.wikia.com/wiki/Rocket_Stove
http://www.homegrownevolution.com/2007/11/our-rocket-stove.html
http://www.rocketstoves.com/pdf/b&w.pdf
Anyway, rocket mass stoves and heaters are SUPER EFFICIENT at burning wood in particular, but they like rolled up phone books, catalogs, newspapers and about anything else you have laying around that will burn!
Three good selling points for me are...
1. DIRT CHEAP TO BUILD!
Most of the time they are made from scrap materials and they are VERY EASY to build!
2. SUPER EFFICIENT means a hand full of twigs will keep you warm for hours!
3. Virtually no SMOKE to give your position away or get in your eyes/shelter when they are in operation!
The super efficiency makes them virtually smoke free if you get the air intake proportions correct!