Just waiting for plann perm before I can start - a big tall shed, not a garage, but insulation important for dry storage.

How about,
Main construction element , 4"/2" or 3/2 wooden studs , 400mm centres, internally braced with full sheets 8'/4' of 9-12mm OSB board ,taped/glued at joins for airtightness ,
External finish ,feather edge boarding , perhaps british grown Cedar , insulate between studs with cheap (DIY shed ie. BQ ) mineral wool
To increase wall depth you could make your own "I" beams 2 x 2"/2" studs with a OSB flange connecting , internal / external stud to a depth of your choice , again internal braced with OSB , external counter battoned and feather edge finish
Roof , pitched , A frame 4"/2" or larger to suit span , again OSB ceiling with mineral wall above
Roof finish 2"/1" batton and Cedar shingles , or second hand tiles , perhap OSB board on pitch for sarking
Concrete/Limecrete slab for base on compacted ground ?

or more than 4m high

One problem is that water running down the outside of the woodwork will rot out the bottom sections and what with splashback from driven rain means that the bottom 9"+ must be truly water resistant*. - build on top of 4 courses of brick? Likewise water ingress under the garage doors, a groove 1/4" wide and the full width of the slab, right in line with the edge of the doors. Also the thermal conduction of the floor must be considered or you will get cold feet when working in it in the winter.

* My wooden shed (1" marine plywood) is built slightly overhanging its slab on wooden joists. The ground is sloping and the slab is surrounded by paving slabs. Where the distance between the wooden planks and the garden slabs is less then 9", the planking is a little rotten. It has been up for 27 years and reproofed every 5 years or so. How DO you paint upwards underneath a floor?.

I do slightly raised slab and one course of bricks stuck on to the slab edge while wet. This seems to be enough to keep the wood up high enough to stay dry and rot free.

Here is one I built about ten years ago

Posted By: tonyHere is one I built about ten years ago

Looks good. What do you call that style of hipped roof where you're left with a small gable?

David

Some years later! The garage was built and the house is in the process of being sold.

This was more of a low-tech / low cost build than anything, and only took a couple of weekends to construct, not including the slab (poured a barrow at a time from a small electric mixer).

The wood was from a small local sawmill but I will use untreated larch or similar for the planking next time.

Following the suggestions above I used 95x35mm treated fence rails to make 12 "A" frames, held together with 3 M12 bolts. These were stood up and temporarily held to the 600mm spacing with battens.
Then the skeleton was wrapped with tyvek, spacers nailed through to the uprights, and then horizontal 18mm planking. At this point it seemed quite rigid (even without a wall plate) so the steel roof was added.
Insulation batts were then placed between the uprights and 9mm OSB screwed in place to walls and ceiling.

Whilst not massively well insulated nor heated it definitely felt nicer than a simple shed or a concrete box to work in and I had no issues with frost or condensation on metal equipment.

Evan - Looks good.

If you want to stain the wood... I've had great success with Ronseal General Purpose wood preserver applied using a small Hoselock plant sprayer. If cleaned out afterwards they survive two or three applications and work out about the same cost as brushes but way easier and quicker.