Your rights are more extensive than your builder is prepared to admit.
The Customer Protection Law (חוק הגנת הצרכן) update of 2011 gives protection to home purchasers of up to 7 years for many waterproofing issues.
I would recommend e-mailing the builder this information (in order to have it in writing). In most cases this should be enough to make him realise that he is dealing with an informed customer.
If you still are not having success please be in contact.
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