single layer of waterproofing for raft foundation

[swelm]

hi

we have raft foundation and contractor refuse to make double layer of waterproofing under the raft
he side the high level of ground water table under the raft by 45 cm and he that that is enough

but i insist in to make two layer he ask me about the reason

but i can not answer

anyone can help

regards

 

[JedClampett]

If it's in the contract documents (specifications or drawings), he agreed to it and has to do it. If it's just a preference from you because you want a belt and suspenders design, he doens't have to do it.