“Javan has gone away from Wales and developed as a person and a player, picking up international experience. He is technically excellent around his set-piece and will add to the Cardiff game model with his work in open play,” said Cardiff head coach Matt Sherratt.
“Sam will add real depth and competition to the tight-head position. He has very good experience for a 27-year-old – playing in the English Premiership at Saracens and the URC (United Rugby Championship) with the Scarlets, while gaining international experience.
“He has a real passion for the set-piece and a great work ethic that will enable him to add to our game model.”
Sebastian said: “I have seen what they have been building at Cardiff over the last couple of years and it’s really exciting.
“Moving closer to home and family is also nice and I’m looking forward to giving 100% for the jersey.”
Wainwright said: “Myself and my family are really grateful for the opportunity Cardiff have given us and we are really looking forward to coming to the capital and linking up with such a great team, with so much history.
“We have heard nothing but good things about Cardiff. It is a great environment for players and their families, which was a big reason for signing.”
The signings come during a torrid period in Welsh professional rugby.
Cardiff have been owned by the Welsh Rugby Union (WRU), which took them out of administration in April amid serious financial difficulties.
Cardiff and Dragons subsequently signed a new deal with the governing body – the new Professional Rugby Agreement (PRA).
Scarlets and Ospreys have not done so and say they asked the WRU for assurances the takeover “will not disproportionally benefit Cardiff and disadvantage the independent clubs” but claim they were not given guarantees.
