Thanks for your responses. I represented it in this way on our plans, but my builder built a stud wall in its place and it now claiming a variation to change it. Do either of you have a reference to text book or something a little 'official' that I could show to my builder to say he misinterpreted the plans?

How could he build a stud wall when you didn't draw any boards to cover the studs with? Clearly he misinterpreted it, although you could have indicated/highlighted the fact it's not an ordinary stud wall. Normally at work we would always specify everything out of the ordinary such as this kind of timber screen/wall with int. elevations, details and notes etc. 

You didn't call it out in any way?????

Regardless of who's fault it is.  Tell the GC to rip the stud wall out and rebuild to your specifications. Lesson learned. 

I would draw it as rectangles and add either crosses, as with any wood framing member section cut, or another hatch pattern. Anything that deviates from standard construction needs to also be called out on the plans, and usually also represented with detail drawings.

Builders routinely fix things that architects missed on plans, so it's not fair to them to show something that looks like you just forgot to add a couple of lines and expect them to know what you intended. 

agree with all above - if you just drew rectangular boxes at best you would have ended up with standard 2x wood studs.  I assume the intention is for a much higher grade of wood with some type of finish on it?  No way for the builder to know this.

We can't be talking about that much $$$ though, if this is your only problem you're doing well.