With JB's method for constructing the base, I believe the walls would be open. If the underside were open for air to circulate freely then no a dpm wouldn't be much use.
I was describing what I would do were there a continuous perimeter wall of blocks/bricks. My presumption causing confusion, sorry there.
The cls does come in 8 or 10ft lengths (2.4 or 3m) Most places only do them in 2.4. Height is up to you, a standard door in a house is about 6'6", 2 metres-ish. I'd consider a minimum height of 2.2m but you can go all the way to 2.4 if you want it to feel nice and spacious inside.
Distance between studs should be at maximum 600mm, 450mm will be be better though. At least one row of noggins down the centre, the height of which should be the same height as the type of insulation you are using, rockwool type come in at 1200mm high, rigid boards usually come in big sheets which will need cutting to size regardless of noggin height.
You will need to temporarily brace the frame work with a long 4x2 diagonally on the inside, to keep it all square before you add the outer boards/cladding.
The ply/osb on the outside isn't strictly necessary, but better for rigidity when building, and security if that will be an factor. 11mm OSB will do the job just fine, you'll get away with 9mm ply if cost is an issue.
You can put it on the inside, under the plasterboard, if you wish.
Breather paper is brown 'wrapping paper' with a waterproof coating, breathable roofing felt would do the same job, only better.
Rockwool slab is fine for the insulation, you will get better performance from celotex/kingspan but at a higher price.
Only use pre-treated timber for the base, the cls should all get a coat of clear wood preserver before construction, although many builders wouldn't bother as it's not overly important if it's built correctly.
Roof should go before insulation or flooring, you can work on a ply temp floor while you are putting the walls up.
Low pitch ok, but fitting a skylight will be tricky at low pitch, I'd be tempted to get a sheet of polycarbonate for a section of the roof, which continues all the way down to the edge of the roof. Or a roof dome of some kind.
I was describing what I would do were there a continuous perimeter wall of blocks/bricks. My presumption causing confusion, sorry there.
The cls does come in 8 or 10ft lengths (2.4 or 3m) Most places only do them in 2.4. Height is up to you, a standard door in a house is about 6'6", 2 metres-ish. I'd consider a minimum height of 2.2m but you can go all the way to 2.4 if you want it to feel nice and spacious inside.
Distance between studs should be at maximum 600mm, 450mm will be be better though. At least one row of noggins down the centre, the height of which should be the same height as the type of insulation you are using, rockwool type come in at 1200mm high, rigid boards usually come in big sheets which will need cutting to size regardless of noggin height.
You will need to temporarily brace the frame work with a long 4x2 diagonally on the inside, to keep it all square before you add the outer boards/cladding.
The ply/osb on the outside isn't strictly necessary, but better for rigidity when building, and security if that will be an factor. 11mm OSB will do the job just fine, you'll get away with 9mm ply if cost is an issue.
You can put it on the inside, under the plasterboard, if you wish.
Breather paper is brown 'wrapping paper' with a waterproof coating, breathable roofing felt would do the same job, only better.
Rockwool slab is fine for the insulation, you will get better performance from celotex/kingspan but at a higher price.
Only use pre-treated timber for the base, the cls should all get a coat of clear wood preserver before construction, although many builders wouldn't bother as it's not overly important if it's built correctly.
Roof should go before insulation or flooring, you can work on a ply temp floor while you are putting the walls up.
Low pitch ok, but fitting a skylight will be tricky at low pitch, I'd be tempted to get a sheet of polycarbonate for a section of the roof, which continues all the way down to the edge of the roof. Or a roof dome of some kind.
. I like the way he did his foundations. Just wondering if this is easier to do for my build? Mainly because I thick obviously as I am unable to work out how I use the water level I brought to make sure the concrete levels in each foundation strip is the same height! (unless I'm again being thick I can't see how the water level would work when the concrete levels are below ground level). Using the technique in the link you gave I only need to make sure the level of the pile shuttering is level and all should be fine.