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Here is a rough estimate of what you'll need 2-1/2" 4x8' cdx ply wood for floor8-1/4" 4x8' luan ply wood for the walls if that is what you will use, paint it 2-1/4" or 3/8" cdx ply wood for roof, your choice on thickness, I use 3/8"2-2"x10"x10' pressure treated(or regular spruce kiln dried your choice)8-2"x4"x93" for the floor joices, you can cut the 3" off a 8' 2x4 and nail it to the inside of your 2x10's to make the floor area 8' wide, i space mine 16" on center. Or you could build a box frame and then put it on your 2x10 ski's then you'll need 2 more 2x4's for that method.For the wall studs I usually rip down 2x4's in half approx to 1 5/8" a 2x4 is 3.5" and usually a table saw blade is 1/8" so you usually end up w/ 1 5/8" x 1.5". 1.5" being the thickness of the 2x4. I still call them 2x2's, I usually space my wall studs at 24" on center no real need to do 16" on center like in a house. 20-2x4x8' ripped in half for the walls. That is w/ no windows, if you want windows than you need to frame them out and that takes more 2x2's. Walls I base on the gable ends to not exceed 8' from the peak of the roof to the floor. Other wise we'd need more ply wood. 5-2x4x10' for roof here is how I do itRoof I always just do a peaked roof, I like them. No slanted or flat roofs for me. I always use a ridge pole as well, then I run my rafters down to my walls. then sheet the roof. I'm tall at 6'7", so I like a tall interior. I put my side wall height at 6'9" and the center of the roof height from the floor at 8'. Rafters I use 2x4's notched out so that they fit over the wall a little bit, so that there is a 1.5" eve, and about 1" gap b/w the roof sheating and the top of the wall for ventilation, I then put my rafters at 24" on center as well. you'll use 5-2x4x10' for that. When I put my roof sheeting up I set it at the edge of the rafters and then nail it down. You'll end up with a gap at the Ridgline for ventilation. for roofing I use single coverage rolled roofing comes in differant colors, I use black b/c it sucks up more of the suns heat which helps to melt off the snow and warm the interior. A single role of this you'll need they are 50' long by 3' wide so you'll have extra left over. I start at the bottom and roll accross, parrallel to the ridge line on both sides, then the final strip accross the top. I use roofing nails, and drip edge on mine its up to you. more or less I build mine like minature house w/ some down size materials. I spend alot of time in it so I also finish the inside. any questions just ask.