[Cob] drainage level

[Predrag Cvetkovic]

I showed one my friend nice Cob Builders handbook from www.weblife.org to
introduce him to cob. He is plumbing and sewerage systems designer.

On page "Foundation Summary" they show a drainage system. The level of
perforated pipe is a bit lower or almost the same as the level of
foundation. My friend suggested that level must be higher, if not, water can
flow under foundation and the foundation can settle. The situation in the
pictire on that page is maybe special one, because of the slope?

I would appreciate your comments.

Predrag Cvetkovic