The Bulls needed 12 tries to pass Loughor and Waunarlwydd into the safety zone but it wasn't to be as they could only muster scores from John Thurston, Shaun Hughes and Fred Lewis. Jonathan Morgan, Barry Maddox and Stewart Phillips replied for the Quins, who finished runners-up to Bonymaen and a nine point cushion over third-placed Narberth.
Despite their relegation, Builth Team Manager Justin Lewis believes his side can bounce back next season. He said, "We left it too late to claw ourselves away and the slow start to the season cost us. We took just one point in 11 games and it's hard to make up that deficit at any level.
"I'm confident though we can come straight back up next season and we will keep the same squad. We had five youth players in our team so the future is looking great for Builth."
In Division One East, Newbridge's dismal end of season form continued when they tasted another defeat after going down 17-13 at mid-table Newport Saracens. Matthew Taylor ran in Newbridge's try but Lee Williams touched down for the Saracens and Darren Gregg added the crucial 12 points with the boot.
Ystrad Rhondda, who looked certain candidates for the dreaded drop a few weeks ago, extended their remarkable recent run with a 45-15 win over Abercynon to send the visitors down. Having notched up 10 points from the last four matches, they now face fellow strugglers Blackwood in the remaining key game.
Elia Tellegrotti and Gareth Fear both grabbed a brace of tries and Captain Cliff Hamley, Nathan Rees and Gareth Pugh ran in a try apiece in their seven-try win. Wayne Jervis added 10 points with the boot to complete the win.
Blackwood kept their survival hopes very much alive by beating UWIC 37-26 to set up the winner-takes-all clash with their relegation rivals.