We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Tim S saying
something like:

This is now making me wonder if I will need pillars to strengthen the wall
- or if a 5m run of single block will be O.K.

The house I grew up in had a standalone brick garage about that length - or
perhaps a little longer. That was single brick wall with one double
thickness butress about halfway along each long side.

The most impressive single-skin brick garage I saw was actually a truck
shed, of about 30' long by 30' wide and two stories empty space. Not a
buttress in sight and...

That didn't fall over.

It had been up for many years, too. Probably fallen over now, mind.