Sack the contractor...

For tiles, u can use MS-1 polymer, a polymer glue which adhere to anything. Expensive but very lasting. I used it to stick stones outside my car porch. Rain or shine, the stones are still there. Best of all, can DIY. Don't need pesky contractors. Or hire 2 Indon workers to help u. Pay around RM 30-40 per day. Must supervise personally.

For staircase balustrade, u can use adhesive or nails.

Post some pics so people can help u.