Mr Maha, whose 8-year-old son James was on the deck where the buffet-style meal had been set up, said the crash was a huge shock.
"We said our family prayer in the living room, and after doing the birthday song and blowing out the candles, then family [members] started to walk to get the food [on the deck]. All of a sudden, bang."
A Fire Service spokesman said emergency services were called just after 4.20pm. About a dozen people were treated at the scene by paramedics, and six were taken to Waitakere Hospital for further treatment.
Said Mr Maha: "Mostly they were really shocked when it happened, but when they settled, it was all right."
James was checked over by emergency staff because "he had a sore bum", but he was fine.
A spokeswoman from the hospital said last night that all of the patients had been discharged.
The collapsed deck, which was on the front of the house, still had emergency tape around it last night.
Mr Maha said it had been used on numerous occasions for family events and never felt unstable.
"It's a good house," Mr Maha said.
He had lived there from 2007 to 2010 with his wife and James before other members of his family took over the lease, he said. No one had had any problems until yesterday.
Police inspector Peter Rayne said as there was no criminal culpability or liability, the matter was not being investigated further.