Where's my damp proof course - Rendered wall

[PatioNovice]

I’m not sure where the damp proof course is in my rendered wall. Three photos show the patio prior to work, the patio with flags and mortar removed, and detail of the hole in the wall.
In the hole is the kitchen waste pipe. You can see a damp proof course on the inner layer of bricks under the floor joists, but nothing visible in the outer layer of bricks.
Could the damp proof course dip down for the patio doors, and then return to a higher level either side of the doors? Is the extra thickness of render on the lower 400mm of the wall significant?
There is no sign of damp on the inside of the house. Your thoughts would be most appreciated. Thanks.
Patio2009

[Pablo]

Depending on how old the house is you may not have one. The plaster detail sometimes indicates a dpc but it is too high in this case. Dpc's are usually at internal floor level or below and if you have wooden floor and not a poured concrete one then they will be at least 150mm below the top it. These are general rules and not always followed.

[PatioNovice]

Thanks Pablo, The house was built in the 1930's and has wooden floors. I've had a bit of a poke around in the hole below the patio doors, and can see traces of the dpc on the outer wall. This dpc (below the patio doors) is 140mm below the final level of the original patio.
My neighbour tell me that the patio was built in the 1960s by a local builder who owned and lived in the house for many years after the work was done. Any idea what he might have done to protect against damp? There is no sign of damp on the internal walls.

[Tony McC]

If you;re uncertain, play it safe and use a level that is at least 150mm (6") below internal floor level.